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  • Interactive effects of vegetation and water table depth on belowground C and N mobilization and greenhouse gas emissions in a restored peatland
    Plant Soil (IF 3.259) Pub Date : 2020-01-27
    Cristina Lazcano, Anoop S. Deol, Martin E. Brummell, Maria Strack

    Abstract Aims This study assesses the relative effects of hydrology and colonization by vascular plants on belowground C and N mobilization, and emission of CO2 and CH4 in an extracted bog under restoration in Alberta (Canada). Methods A wet (high water table) and dry (low water table) area were identified at the site and plots with cottongrass (Eriophorum vaginatum) or bare peat were established in each area. Plant growth, peat and porewater dissolved C (DOC) and N (TDN), microbial biomass and the emissions of CO2 and CH4 were monitored at the plots throughout the growing season. Results The largest concentrations of DOC were measured in dry and bare sites. Lower E2:E3 ratios suggested a higher aromaticity of the DOC at these sites that were net sources of CO2 and CH4. The concentration of TDN was greater in plots with cottongrass and high water table, supporting a more abundant microbial biomass. Cottongrass dominated plots also had larger gas emissions as compared to bare plots even though they were net C sinks due to their high photosynthetic rates. Conclusion Maintaining a high water table is key to reducing peatland C losses. While vascular plant presence seems to prime the release of N and greenhouse gases, the inputs of C exceeded the losses and recovered the C sink function of the peatland ecosystem in the short term. Carbon inputs are maximized under high water table and plant presence.

    更新日期:2020-01-27
  • Differential functional traits underlying the contrasting salt tolerance in Lepidium species
    Plant Soil (IF 3.259) Pub Date : 2020-01-27
    R. Hajiboland, S. Bahrami-Rad, N. Zeinalzade, E. Atazadeh, H. Akhani, C. Poschenrieder

    Abstract Aims To explore the mechanisms responsible for salt tolerance in Brassicaceae species, a multifactorial approach was used to clarify the functional traits underlying the differential salt tolerance in two Lepidium species, namely the halophyte L. latifolium and its glycophyte relative, L. sativum. Methods Parameters related to photosynthesis, nitrogen assimilation, ion accumulation, water relations and succulence, osmotic adjustment, phenolics metabolism, antioxidative defense, nitric oxide (NO) level and the expression of Na+ antiporter (SOS1 and NHX) were analyzed in plants grown under salt stress in hydroponics. Results In addition to significant differences regarding the majority of salt tolerance indicators, a characteristic early boost, 52 h after exposure to salt, was observed in the concentration of H2O2 and NO in the halophyte, which was almost absent in the glycophyte. Following the application of detrended component analysis, discrimination between the glycophyte and halophyte could only be performed via temporal curves in the antioxdative components and NO, and less effectively, by phenolics metabolism. Conclusion H2O2 and NO signaling and the adaptive modification of phenolics metabolism play crucial roles in determining the halophytic behavior of L. latifolium. These data may result in new insights concerning the studies on halophytism in the Brassicaceae.

    更新日期:2020-01-27
  • Correction to: Linear relation between leaf xylem water potential and transpiration in pearl millet during soil drying
    Plant Soil (IF 3.259) Pub Date : 2020-01-24
    Gaochao Cai, Mutez Ali Ahmed, Michaela A. Dippold, Mohsen Zarebanadkouki, Andrea Carminati

    In the original version of this article, equations 4 and 9 unfortunately contained errors

    更新日期:2020-01-24
  • Response of bacterial communities and plant-mediated soil processes to nitrogen deposition and precipitation in a desert steppe
    Plant Soil (IF 3.259) Pub Date : 2020-01-22
    Zhen Wang, Risu Na, Liz Koziol, Michael P. Schellenberg, Xiliang Li, Na Ta, Ke Jin, Hai Wang

    Abstract Background and aims Changes in nitrogen (N) and precipitation levels can substantially alter soil properties and plant growth, thereby altering soil microbial diversity and functionality. Method We used manipulated precipitation treatments (50% reduction, control, and plus 50%) and tested two N fertilization levels (control and plus 35 kg N ha−1 yr−1) from a 4-year field experiment to evaluate the effects on soil bacterial diversity, community composition, and N-cycle gene abundance. Results N additions significantly increased ammonia-oxidizing bacterial abundance (via AOB-amoA) but decreased denitrification genes (i.e., nirS and nosZ). Decreased precipitation significantly decreased the abundance of N-cycle genes (AOB-amoA, nirS, and nosZ), while increased precipitation conversely increased the abundance of these same genes. Decreased precipitation led to differences in the microbial community composition that favored drought resistance, indicating that plant-associated microbiomes may be able to modulate plant growth fitness in the context of extreme environmental conditions. N additions substantially altered soil bacterial communities, increasing the relative abundance of certain bacteria and of nitrification-related genes in a manner that depended on precipitation fluctuations. Conclusions Differences in the bacterial community composition and N-cycle genes determined the functional response of a grassland ecosystem to decreased precipitation conditions, and therefore could affect the influence of N deposition on plant growth as well as the physical and chemical properties of the soil.

    更新日期:2020-01-23
  • Both vacant niches and competition-trait hierarchy are useful for explaining the invasion of Caragana microphylla into the semi-arid grassland
    Plant Soil (IF 3.259) Pub Date : 2020-01-21
    Ke Dong, Yujuan Xu, Guang Hao, Nan Yang, Nianxi Zhao, Yubao Gao

    Abstract Aims Trait-based coexistence theories are useful to explain community processes. The aim was to distinguish which theory played a more important role in explaining the invasion mechanism of Caragana microphylla into communities in the Eurasian semi-arid grassland region. Method We conducted a water condition (WC) × neighbouring plant diversity (NSD) experiment, measured functional dispersion (FDis) and biomass of neighbours, absolute and hierarchical distances between neighbours and C. microphylla for plant height, specific leaf area and leaf dry matter content (LDMC), and explored the relative effect of each predictor on neighbour-effect intensity index (NIntA) on C. microphylla. Results Significant effect of NSD was direct or mediated by cascading effects between FDis and biomass of neighbours, significant effect of WC was direct or mediated by LDMC hierarchical distance, shoot biomass of neighbours mediated indirect effects of both NSD and WC on the NIntA on C. microphylla. None of the trait absolute distances was employed to explain the variability of the NIntA on C. microphylla. Conclusions The reduction of NSD or water could decrease the inhibitory effects of neighbours on C. microphylla by increasing vacant niches or increasing the LDMC hierarchical distance between neighbours and C. microphylla, respectively, suggesting that vacant niches and competition-trait hierarchy played more important roles than competition-trait similarity in explaining shrub invasion processes in the Eurasian semi-arid grassland region.

    更新日期:2020-01-22
  • Do diversity of plants, soil fungi and bacteria influence aggregate stability on ultramafic Ferralsols? A metagenomic approach in a tropical hotspot of biodiversity
    Plant Soil (IF 3.259) Pub Date : 2020-01-21
    Julien Demenois, Luis Merino-Martín, Nicolas Fernandez Nuñez, Alexia Stokes, Fabian Carriconde

    Abstract Aims Understanding how soil aggregate stability (MWD) is influenced by microbial diversity and abundance can be crucial for ecological restoration in severely disturbed areas. We investigated the relationships between plant and soil microbial diversity and MWD of an ultramafic Ferralsol along a vegetational succession gradient in New Caledonia, where wildfires and extensive nickel mining have degraded the landscape. Methods Five plant communities were studied. For each one, MWD, soil physicochemical parameters (e.g. soil organic carbon (SOC)), plant root traits and fungal abundance were measured. The diversity and structure of plant and microbial communities were respectively assessed via botanical inventories and a metagenomic approach. A generalized linear model (GLM) was used to assess the influence of diversity indexes on MWD. Constrained ordinations (CCA) were performed to assess the influence of communities’ structures on MWD. Results GLM highlighted the linkage between SOC and MWD but did not identify any significant influence of diversity indexes on MWD. CCA revealed a significant influence of communities’ structures, especially the abundance of saprotrophic fungi, on MWD. Conclusions We showed that the structure, but not species richness and diversity of plants, soil fungi and bacteria influence aggregate stability on Ferralsols.

    更新日期:2020-01-22
  • Metamodelling a 3D architectural root-system model to provide a simple model based on key processes and species functional groups
    Plant Soil (IF 3.259) Pub Date : 2020-01-21
    Loïc Pagès, Olivia Pointurier, Delphine Moreau, Anne-Sophie Voisin, Nathalie Colbach

    Abstract Aims The architecture of root systems determines where and how much resources plants can extract from the soil, how they compete for soil resources, and how they interact with soil organisms. We aimed to develop a 3D root-system model called RSCone for future inclusion into multispecies individual-based canopy models suitable to design integrated weed management or intercropping strategies. Methods We (1) proposed a conceptual root-system model consisting of empirical equations predicting root-system envelope, root length and biomass distribution from environmental conditions, species and plant stage, (2) calibrated the model from simulations with an existing architectural root-system model (ArchiSimple) to benefit from its knowledge on root functioning and the many parameterized crop and weed species, (3) identified the root-system architectural processes driving the key root state variables and (4) established species functional groups with Principal Component Analyses and clustering. Results RSCone consists of 17 equations and 14 parameters; it was calibrated for 22 weeds and 22 crop species and varieties. Six species functional groups were established, depending on their family (Poaceae, Fabaceae, other), root-extension rates, specific root length (SRL) and the time to reach maximum SRL. Conclusion RSCone is ready to be included into multispecies (crop and/or weed) dynamics models.

    更新日期:2020-01-22
  • High ecosystem multifunctionality under moderate grazing is associated with high plant but low bacterial diversity in a semi-arid steppe grassland
    Plant Soil (IF 3.259) Pub Date : 2020-01-21
    Xinyu Wang, Frank Yonghong Li, Yanan Wang, Xinmin Liu, Jianwei Cheng, Junzhen Zhang, Taogetao Baoyin, Richard D. Bardgett

    Abstract Aims Current studies on the relationship between biodiversity and ecosystem functioning have mostly focused on plant communities. Less is known about the individual and combined effects of biodiversity components above-and-below-ground on ecosystem multifunctionality. The aim of this study was to explore how different management regimes influence multifunctionality via modification of both plant and soil microbial (bacterial and fungal) diversity. Methods We used a 6-year experiment in Inner Mongolian grassland to compare multifunctionality and separate functions related to the C, N, P cycles and plant productivity under four management regimes and examine relationships between these functions and different components of biodiversity, both above- and belowground. Results Ecosystem multifunctionality and the rates of nutrient cycling and plant productivity, were greatest under moderate grazing intensity, and lowest under no grazing. Further, across all management regimes, multifunctionality was positively related to plant diversity, and plant and soil microbial diversity combined explained a much greater (62.5%) proportion of variance in multifunctionality than that did either component alone. Different components of biodiversity showed contrasting relationships with individual functions: plant diversity was positively related to C and N cycling, whereas bacterial diversity was negatively related to P cycling and plant productivity. Conclusions Moderate grazing has better outcomes for biodiversity conservation and ecosystem multifunctionality than mowing and cessation of grazing. Sustainable grazing management is a viable strategy to conserve both above- and belowground biodiversity and enhance the delivery of multiple ecosystem functions.

    更新日期:2020-01-22
  • The fertile island effect collapses under extreme overgrazing: evidence from a shrub-encroached grassland
    Plant Soil (IF 3.259) Pub Date : 2020-01-15
    Yurong Cai, Yuchun Yan, Dawei Xu, Xingliang Xu, Chu Wang, Xu Wang, Jinqiang Chen, Xiaoping Xin, David J Eldridge

    Woody plant encroachment is a phenomenon of global concern in drylands due to demonstrated reductions in livestock carrying capacity. However, shrubs are known to contribute to the development of patches of enhanced fertility that might offset any negative effects of increasing grazing. We measured soil physical and chemical characteristics within shrub and open patches across a gradient in livestock grazing to explore how the relative effect of shrubs might change with increasing grazing-induced disturbance.

    更新日期:2020-01-15
  • Soil bacteria and fungi respond differently to plant diversity and plant family composition during the secondary succession of abandoned farmland on the Loess Plateau, China
    Plant Soil (IF 3.259) Pub Date : 2020-01-14
    Zekun Zhong, Xinyi Zhang, Xing Wang, Shuyue Fu, Shaojun Wu, Xuqiao Lu, Chengjie Ren, Xinhui Han, Gaihe Yang

    Abstract Aims This study aimed to determine the responses of soil bacteria and fungi to plant species diversity and plant family composition (PFC) following secondary succession on former farmland (FL). Methods Illumina sequencing of 16S rRNA and ITS genes was used to determine soil microbial communities along a chronosequence of FL left abandoned for 0, 10, 20, 30, 40, and 50 years on the Loess Plateau. Soil properties, plant diversity, and PFC were also investigated. Results Fungal communities were dominated by Ascomycota and Basidiomycota. Fungal diversity and Ascomycota abundance increased with time, while Basidiomycota abundance decreased. The fungal diversity and dominant phyla were related to the increasing levels of plant species diversity and evenness with succession. Bacterial diversity first increased and then decreased as succession proceeded, peaking at 30 years. Bacterial communities transitioned from Actinobacteria to Proteobacteria dominance during the first 30 years, after which Actinobacteria was dominant. Plant family composition exerted indirect effects on the diversity and dominant phyla of bacterial communities, mainly through direct effects on soil organic carbon and total nitrogen content. Bacterial diversity and Proteobacteria abundance were higher at Leguminosae- and Gramineae-dominant succession stages, but lower in Compositae-dominant plots; Actinobacteria showed the opposite result. Conclusions Plant species diversity and evenness might be the key drivers for shaping fungal communities, but bacteria are influenced more by changes in PFC and abiotic soil nutrient levels during succession.

    更新日期:2020-01-14
  • NAC transcription factors from Aegilops markgrafii reduce cadmium concentration in transgenic wheat
    Plant Soil (IF 3.259) Pub Date : 2020-01-14
    Xuye Du, Fang He, Bin Zhu, Mingjian Ren, Heng Tang

    Abstract Background and aims Cadmium (Cd) is one of the heavy metal elements that are most harmful to human health, and the transmission of Cd through the food chain is a global issue. Aegilops markgrafii is a wild relative of the cultivated wheat that is tolerant of high levels of Cd. The objective of this study is to investigate the NAC transcription factors (TFs) involved in Cd tolerance in Ae. markgrafii and to verify their function in transgenic wheat. Methods We cloned NAC TFs from Ae. markgrafii plants exposed to excessive Cd treatment. The expression profiles of NAC TFs in root and shoot tissues were examined using qRT-PCR. Transgenic wheat was obtained via Agrobacterium-mediated transformation. Finally, we examined Cd concentrations in transgenic wheat under excess Cd treatment. Results We identified three NAC TFs and classified them into four subfamilies. Sequence alignments showed that the NAC TFs had conserved N-terminal domains but varied C-terminal domains. Expression profiles of NAC TFs showed about 150-fold up-regulation in the transcription of AemNAC2 and AemNAC3 under excess Cd treatment. Overexpression of AemNAC2 in the wheat cultivar ‘Bobwhite’ led to reduce Cd concentration in the root, shoot and grains. Conclusions AemNAC2 is an important TF that contributes to Cd tolerance in wheat.

    更新日期:2020-01-14
  • Cytokinin dynamics in xylem sap and leaves of fruiting and de-fruited sunflower hybrids of contrasting post-anthesis canopy senescence patterns during flowering and grain-filling
    Plant Soil (IF 3.259) Pub Date : 2020-01-13
    Mariano A. Mangieri, Antonio J. Hall, Claudio A. Chimenti

    To determine whether xylem sap and leaf cytokinin levels were associated with live root length density (LRLD) and leaf senescence, these variables were measured in intact (control) plants and those from which florets were removed, in hybrids of contrasting post-anthesis senescence patterns.

    更新日期:2020-01-13
  • Intercropping with wheat suppressed Fusarium wilt in faba bean and modulated the composition of root exudates
    Plant Soil (IF 3.259) Pub Date : 2020-01-11
    Jiaxing Lv, Yan Dong, Kun Dong, Qian Zhao, Zhixian Yang, Ling Chen

    The causal agent of Fusarium wilt in faba bean is Fusarium oxysporum f. sp. fabae (FOF), which significantly reduces the yield in continuous cropping systems. We aimed to evaluate the role of wheat in alleviating Fusarium wilt in faba bean.

    更新日期:2020-01-13
  • Induced systemic resistance - like responses elicited by rhizobia
    Plant Soil (IF 3.259) Pub Date : 2020-01-11
    María Laura Tonelli, María Soledad Figueredo, Johan Rodríguez, Adriana Fabra, Fernando Ibañez

    Rhizobia are soil bacteria that engage into a mutualistic symbiosis with plants and benefit the host by fixing atmospheric N. In addition, rhizobia can be considered as biocontrol agents, contributing to plant health through direct inhibition of a wide range of pathogens. More recently, it became evident that rhizobial invasion of plant roots can also trigger an increased systemic resistance state in the host, a process resembling the Induced Systemic Resistance (ISR) mechanism. However, this indirect biocontrol property of rhizobia was relatively less explored.

    更新日期:2020-01-13
  • Accumulation and partitioning of rare earth elements in olive trees and extra virgin olive oil from Adriatic coastal region
    Plant Soil (IF 3.259) Pub Date : 2020-01-10
    Filip Pošćić, Mirella Žanetić, Željka Fiket, Martina Furdek Turk, Nevenka Mikac, Niko Bačić, Mavro Lučić, Marija Romić, Helena Bakić, Maja Jukić Špika, Branimir Urlić, Marko Runjić, Gabriela Vuletin Selak, Elda Vitanović, Tatjana Klepo, Jakša Rošin, Zed Rengel, Slavko Perica

    A potential of rare earth elements (including yttrium) (REY) accumulation in olives is increasing due to enhanced use of REY in human activities. REY transfer to extra virgin olive oil (EVOO) is little studied, and characterising the relationships between soil properties and REY concentrations in olive leaves, pomace and EVOO can enhance our understanding of soil-plant interactions.

    更新日期:2020-01-11
  • Plant uptake of nitrogen and phosphorus among grassland species affected by drought along a soil available phosphorus gradient
    Plant Soil (IF 3.259) Pub Date : 2020-01-10
    Pierre Mariotte, Tom Cresswell, Mathew P. Johansen, Jennifer J. Harrison, Claudia Keitel, Feike A. Dijkstra

    Here we assessed N and P uptake of four grassland species grown together in response to a short-term drought event along a soil P gradient.

    更新日期:2020-01-11
  • Mycorrhizal impacts on root trait plasticity of six maize varieties along a phosphorus supply gradient
    Plant Soil (IF 3.259) Pub Date : 2020-01-09
    Xin-Xin Wang, Hongbo Li, Qun Chu, Gu Feng, Thomas W. Kuyper, Zed Rengel

    Plasticity of plants refers to their ability to produce different phenotypes in different environments. Plants show plasticity aboveground as well as belowground. The influence of the arbuscular mycorrhizal fungal (AMF) symbiosis on root plasticity is poorly known. This study aimed to quantify plasticity of root-system related, morphological, physiological or mycorrhizal traits along a soil phosphorus (P) supply gradient.

    更新日期:2020-01-09
  • Contrasting effects of light, soil chemistry and phylogeny on leaf nutrient concentrations in cave-dwelling plants
    Plant Soil (IF 3.259) Pub Date : 2020-01-09
    Kundong Bai, Yigang Wei, Denan Zhang, Longfei Fu, Shihong Lv, Lili Deng

    Abstract Background and aims The drivers of variations in leaf nutrient concentrations in cave-dwelling plants remain poorly understood. We aimed to explore the effects of light, soil chemistry and phylogeny on leaf nutrient concentrations in cave-dwelling plants. Methods We quantified light availability and sampled top-soils and leaves of the co-existing herbs and ferns in three caves. We used the traditional and phylogenetic comparative methods to determine the effects of light, soil chemistry and phylogeny on leaf nutrient concentrations and the cross-species correlations between leaf nutrients. Results Leaf nutrient concentrations differed little among caves due to the non-significant relationships of leaf nutrient concentrations with light availability and soil nutrient concentrations across caves. The phylogenetic signals in leaf nutrient concentrations were significant for Ca, Mg and N but non-significant for the remaining nutrients. The evolutionary rates of leaf nutrient concentrations tended to increase with decreasing phylogenetic signals and were faster in herbs than ferns. These contrasting degrees of phylogenetic conservatism in leaf nutrient concentrations were best generated by Ornstein-Uhlenbeck models, i.e., stabilizing selection towards an optimum across species for P, K, S, Fe, Mn and Zn or higher optimal concentrations in herbs than ferns for Ca, Mg and N. Strong cross-species correlations between leaf nutrient concentrations such as Ca vs Mg and N vs P were found. Conclusions Leaf nutrient concentrations in cave-dwelling plants showed convergent adaptations to cave environments and presented contrasting degrees of phylogenetic conservatism to produce leaf nutritional diversity for the co-existing herbs and ferns in caves.

    更新日期:2020-01-09
  • Streptomyces sp. LH 4 promotes plant growth and resistance against Sclerotinia sclerotiorum in cucumber via modulation of enzymatic and defense pathways
    Plant Soil (IF 3.259) Pub Date : 2020-01-09
    Bong-Gyu Mun, Won-Hee Lee, Sang-Mo Kang, Sang-Uk Lee, Seok-Min Lee, Dong Yeol Lee, Muhammad Shahid, Byung-Wook Yun, In-Jung Lee

    Abstract Background In the soil ecosystem, microbial diversity exists and these diverse organisms interact with plant roots and influence the physicochemical properties of plants. Some of these diverse microorganisms can cause diseases or can provide beneficial interactions with plants. Rhizobacteria are well-known beneficial microorganism that colonize the plant root zone (rhizosphere) and are referred to as plant growth-promoting rhizobacteria (PGPR) that contribute to the promotion of plant growth either directly or indirectly. PGPRs are also known for their biocontrol abilities. Sclerotinia sclerotiorum, an Ascomycetous soil inhabiting fungus, causes white rot disease in cucumbers. This disease results in the loss of millions of dollars annually. The current study was conducted to isolate naturally occurring soil inhabiting bacteria that may promote plant growth under diseased conditions and also antagonize the pathogen. Scope The isolated LH4 strain was identified as Streptomyces sp. by 16S rRNA sequencing and phylogenetic analysis. The plant growth promoting effects and the antifungal antagonistic activities against Sclerotinia sclerotiorum were confirmed by measuring enzymatic activity of LH4 and demonstration in planta. In addition, Streptomyces sp. LH4 pure culture application exhibited significant growth inhibition of S. sclerotiorum in cucumber. Analysis of the major hormones related to pathogen defense; the jasmonic acid, and salicylic acid, showed that the modulation of these two hormones increased disease resistance in cucumber. Conclusion The present study suggests a possible dual role of Streptomyces sp. LH4 as functional material for bio-fertilizer and biocontrol against pathogens.

    更新日期:2020-01-09
  • Distinct factors drive the assembly of quinoa-associated microbiomes along elevation
    Plant Soil (IF 3.259) Pub Date : 2020-01-08
    Zhiquan Cai, Xiaobo Wang, Sreetama Bhadra, Qi Gao

    Unravelling the factors shaping microbial community structure across plant holobiont is required to promote plant health and crop productivity.

    更新日期:2020-01-08
  • Interactions between intercropped Avena sativa and Agropyron cristatum for nitrogen uptake
    Plant Soil (IF 3.259) Pub Date : 2020-01-06
    Min Liu, Huimin Li, Jingjing Song, Minghua Song, Na Qiao, Yuqiang Tian, Yanjie Liu, Haishan Niu

    The effect of cropping regime on nitrogen (N) uptake in two coexisting plant grass species (Avena sativa and Agropyron cristatum) was investigated.

    更新日期:2020-01-06
  • Arbuscular mycorrhiza contributes to the control of phosphorus loss in paddy fields
    Plant Soil (IF 3.259) Pub Date : 2020-01-06
    Shujuan Zhang, Xinyue Guo, Wenfei Yun, Yu Xia, Zhaoyang You, Matthias C. Rillig

    Abstract Aims Phosphorus (P) loss from paddy fields is a significant issue in sustainable rice production by threatening water environments. We aimed to examine the suitability of mycorrhiza-defective rice (non-mycorrhizal) and its mycorrhizal progenitor to evaluate P loss control via arbuscular mycorrhizal (AM) fungi. We also aimed to investigate the AM effect on P loss via runoff and leaching. Methods We grew the two rice lines in microcosms with and without AM fungi, measured P loss via runoff and leaching before and after nitrogen–phosphorus–potassium fertilization, and quantified plant P content and soil P concentration after the final harvest. Results Mycorrhizal and non-mycorrhizal rice pair systems in the absence of AM fungi had similar plant, soil, runoff, and leachate P contents (except PO43−). In the presence of AM fungi, the concentrations of all P forms in runoff water and leachate in mycorrhizal rice were lower than those in nonmycorrhizal rice regardless of their solubility in water and availability to plants. The cumulative P loss from mycorrhizal systems was 10% less than that from their nonmycorrhizal counterparts. Conclusions This mycorrhizal/non-mycorrhizal rice pair is an efficient experimental tool for research on the control of P loss from paddy fields with AM fungi. AM colonization contributes to the sustainability of rice production by decreasing P loss from paddy fields.

    更新日期:2020-01-06
  • Differential effects of grazing, water, and nitrogen addition on soil respiration and its components in a meadow steppe
    Plant Soil (IF 3.259) Pub Date : 2020-01-04
    Yunbo Wang, Deli Wang, Baoku Shi, Wei Sun

    Abstract Background and aims Understanding the influences of environmental variation and anthropogenic disturbance on soil respiration (RS) is critical for accurate prediction of ecosystem C uptake and release. However, surprisingly, little is known about how soil respiration and its components respond to grazing in the context of global climate change (i.e., precipitation or nitrogen deposition increase). Methods We conducted a field manipulative grazing experiment with water and nitrogen addition treatments in a meadow grassland on the Songnen Plain, China, and assessed the combined influences of grazing and global change factors on RS, autotrophic respiration (RA), and heterotrophic respiration (RH). Results Compared with the control plots, RS, RA and RH all exhibited positive responses to water or nitrogen addition in the wet year, while a similar effect occurred only for RH in the dry year. The responses of RS to precipitation regimes were dominated by both frequency and amount. However, grazing significantly inhibited both soil respiration and its components in all subplots. Further analysis demonstrated that the plant root/shoot ratio, belowground biomass and microbial biomass played dominant roles in shaping these C exchange processes. Conclusion These findings suggest that changes in precipitation regimes, nitrogen deposition, and land utilization may significantly alter soil respiration and its component processes by affecting local carbon users (roots and soil microorganism) and carbon substrate supply in meadow steppe grasslands. The future soil carbon sequestration in the studied meadow steppe will be benefited more by the moderate grazing disturbance.

    更新日期:2020-01-04
  • The role of small molecules in restricting rice accumulation of dimethylarsinic acid
    Plant Soil (IF 3.259) Pub Date : 2020-01-04
    Matt A. Limmer, Angelia L. Seyfferth

    Abstract Aims Dimethylarsinic acid (DMA), an organic arsenic compound found in rice grain, is a causal agent of straighthead disorder, which can decimate yields. To minimize rice accumulation of DMA, we tested 9 molecules for antagonistic effects with DMA. We also tested whether the source of nitrogen is able to affect DMA uptake, as DMA is a weak acid and different nitrogen sources have differing effects on rhizospheric pH. Methods We grew rice (Oryza sativa L. cv. Lemont) hydroponically to maturity in two different experiments. First, 9 potential competitors (boric acid, calcium, glycerol, glycine, lactic acid, phosphoric acid, serine, silicic acid, and urea) were included in the hydroponic solution at a molar ratio ≥ 100:1 competitor:DMA. Second, rice receiving 5 μM DMA was grown under ammonium, nitrate, or a 1:1 mix of ammonium and nitrate. Yield metrics and plant elemental concentrations were measured after harvest. Results Of the potential competitors, only silicic acid was able to alleviate straighthead disorder and no competitors were able to reduce grain As by ≥30%. Under differing nitrogen sources, nitrate decreased plant concentrations of As relative to ammonium, but not in the grain. Conclusions While Si can alleviate DMA uptake, there remains uncertainty in how most DMA enters the plant.

    更新日期:2020-01-04
  • Linear relation between leaf xylem water potential and transpiration in pearl millet during soil drying
    Plant Soil (IF 3.259) Pub Date : 2020-01-03
    Gaochao Cai, Mutez Ali Ahmed, Michaela A. Dippold, Mohsen Zarebanadkouki, Andrea Carminati

    As soil dries, the loss of soil hydraulic conductivity limits water supply to the leaves, which is expected to generate a nonlinear relationship between leaf water potential (ψleaf) and transpiration (E). The effect of soil drying and root properties on ψleaf and E remains elusive.

    更新日期:2020-01-04
  • Fungal endophytic communities of two wild Rosa varieties and the role of an endophytic Seimatosporium sp. in enhancing host plant powdery mildew resistance
    Plant Soil (IF 3.259) Pub Date : 2020-01-03
    Yi Zhao, Xiu-ling Ji, Ting Shen, Wen-ting Tang, Shao-shi Li, Zheng-qing Zhu, Jitendra Kumar, Hai-yan Li

    Abstract Aims The aim of the study was to evaluate the possible role of endophytic fungi (EF) on Rosa powdery mildew (PM) resistance. Methods The endophytic fungal communities of two wild Rosa varieties with different PM susceptibilities were investigated through both culture-dependent and independent methods, and the antagonistic activities of endophytes against the PM pathogen were evaluated by pot experiments. Results There were more OTUs recovered from the PM resistant variety than from the PM susceptible variety. Similarly, the culturable EF from the PM resistant variety (1333 isolates) was more than that from the PM susceptible variety (670 isolates). Consistent with this, the colonization rate of culturable EF of the PM resistant variety was significantly higher than that of the PM susceptible variety at each PM stage (p < 0.05). In addition, it was found that the dominant EF of both varieties were different using culture-dependent and independent methods. The α-diversity of both culturable and un-culturable EF were similar except at the early stage of PM infection. Pot experiments showed that the strain M7SB 41 (Seimatosporium sp.) from PM resistant variety significantly enhanced host plant PM resistance. Conclusions The results suggested that the endophytic fungal communities of two wild Rosa varieties with different PM susceptibilities were significantly different, and the PM resistant Rosa variety harbored more EF than susceptible Rosa variety, and some EF played an important role in host plant PM resistance.

    更新日期:2020-01-04
  • Interaction of phytohormone-producing rhizobia with sugarcane mini-setts and their effect on plant development
    Plant Soil (IF 3.259) Pub Date : 2020-01-03
    Natália S. Ferreira, Gustavo F. Matos, Carlos H. S. G. Meneses, Veronica M. Reis, Janaina R. C. Rouws, Stefan Schwab, José I. Baldani, Luc F. M. Rouws

    Rhizobia are common members of plant microbiomes. This study aimed to evaluate if rhizobia can colonize sugarcane mini-setts and if and how they affect sprouting and morphological traits of plant development.

    更新日期:2020-01-04
  • Plasticity of barley in response to plant neighbors in cultivar mixtures
    Plant Soil (IF 3.259) Pub Date : 2019-12-26
    Iris Dahlin, Lars P. Kiær, Göran Bergkvist, Martin Weih, Velemir Ninkovic

    Cultivar mixtures can increase productivity through complementarity in resource use, but reported results are often conflicting and the role of plasticity in shaping plant-plant interactions is poorly understood. We aim to determine if individual cultivars show different phenotypic responses when grown in a mixture, whether these responses depend on the neighboring cultivar identity, and how they contribute to variations in productivity and nitrogen (N) use.

    更新日期:2020-01-04
  • Spatial patterns in soil organic matter dynamics are shaped by mycorrhizosphere interactions in a treeline forest
    Plant Soil (IF 3.259) Pub Date : 2019-12-26
    Nina L. Friggens, Thomas J. Aspray, Thomas C. Parker, Jens-Arne Subke, Philip A. Wookey

    Abstract Aims In the Swedish sub-Arctic, mountain birch (Betula pubescens ssp. czerepanovii) forests mediate rapid soil C cycling relative to adjacent tundra heaths, but little is known about the role of individual trees within forests. Here we investigate the spatial extent over which trees influence soil processes. Methods We measured respiration, soil C stocks, root and mycorrhizal productivity and fungi:bacteria ratios at fine spatial scales along 3 m transects extending radially from mountain birch trees in a sub-Arctic ecotone forest. Root and mycorrhizal productivity was quantified using in-growth techniques and fungi:bacteria ratios were determined by qPCR. Results Neither respiration, nor root and mycorrhizal production, varied along transects. Fungi:bacteria ratios, soil organic C stocks and standing litter declined with increasing distance from trees. Conclusions As 3 m is half the average size of forest gaps, these findings suggest that forest soil environments are efficiently explored by roots and associated mycorrhizal networks of B. pubescens. Individual trees exert influence substantially away from their base, creating more uniform distributions of root, mycorrhizal and bacterial activity than expected. However, overall rates of soil C accumulation do vary with distance from trees, with potential implications for spatio-temporal soil organic matter dynamics and net ecosystem C sequestration.

    更新日期:2020-01-04
  • Fine root classification matters: nutrient levels in different functional categories, orders and diameters of roots in boreal Pinus sylvestris across a latitudinal gradient
    Plant Soil (IF 3.259) Pub Date : 2019-12-21
    Joanna Mucha, Marcin Zadworny, Heljä-Sisko Helmisaari, Bengt Nihlgård, Tapani Repo, Maciej Żytkowiak, Stanisław Małek, Peter B. Reich, Jacek Oleksyn

    Fine roots and their symbionts are the key drivers of processes such as nutrient cycling and belowground productivity. Their function depends on position in a branching hierarchy, with absorptive roots (responsible for resource acquisition), and transport roots.

    更新日期:2020-01-04
  • Positive legacy effect of previous legume proportion in a ley on the performance of a following crop of Lolium multiflorum
    Plant Soil (IF 3.259) Pub Date : 2019-12-20
    Aaron Fox, Matthias Suter, Franco Widmer, Andreas Lüscher

    Abstract Aims We investigated the legacy effects of a previous ley’s legume proportion on the performance of a following grass crop in a rotation. Methods In April 2015, a pure Lolium multiflorum L. crop was sown after the removal of legume containing swards (0–100% legumes), and was harvested four times over the following one-year period (3 times in 2015 and once the following April 2016). Labeled 15N fertilizer (50 kg N ha−1) was applied during the 2nd and 3rd re-growth periods to determine N fluxes. Results Across the one-year period, a significant legume-legacy induced increase in biomass yield of L. multiflorum was observed over the entire range of previous legume proportions when compared against the non-legume ley, the effect being 2.15 and 1.73 t ha−1 (P ≤ 0.001 each) in swards with 50% and 100% previous legume proportion, respectively, or up to +31%. The legume-legacy effect on biomass yield was most pronounced at the 1st harvest (June) and persisted into the 2nd harvest in August (P ≤ 0.05 both, over the entire range of previous legume proportion), though was no longer evident at the 3rd harvest (September). Importantly, the legume-legacy effect returned in the 4th harvest in April (P ≤ 0.05). Examining the source of N contributing to N yield confirmed that more N was derived from the soil at harvest 1 and 2 for previous legume containing leys (P ≤ 0.001) compared to those which contained no legumes, with a significant increase still seen for legume mixtures at harvest 3 (P ≤ 0.01). Conclusions The results demonstrate a sustained soil-transferred performance-enhancing legacy effect on a following crop in a rotation, with previous legume proportions of 50% having a comparable effect compared with that of a previous legume monoculture.

    更新日期:2020-01-04
  • Natural variation of nickel, zinc and cadmium (hyper)accumulation in facultative serpentinophytes Noccaea kovatsii and N. praecox
    Plant Soil (IF 3.259) Pub Date : 2019-12-19
    Tomica Mišljenović, Slobodan Jovanović, Nevena Mihailović, Boško Gajić, Gordana Tomović, Alan J. M. Baker, Guillaume Echevarria, Ksenija Jakovljević

    Data on the variability of hyperaccumulation potential of the facultative serpentinophytes Noccaea kovatsii and N. praecox on different geological substrates are scarce. The aim of this study was to assess the accumulation potential of these two species from ultramafic and non-ultramafic substrates, with special emphasis on the hyperaccumulation of Ni, Zn and Cd.

    更新日期:2020-01-04
  • Aboveground resource allocation in response to root herbivory as affected by the arbuscular mycorrhizal symbiosis
    Plant Soil (IF 3.259) Pub Date : 2019-12-18
    Adam Frew, Jeff R. Powell, Scott N. Johnson

    Abstract Aims Arbuscular mycorrhizal (AM) fungi associate with the majority of terrestrial plants, influencing their growth, nutrient uptake and defence chemistry. Consequently, AM fungi can significantly impact plant-herbivore interactions, yet surprisingly few studies have investigated how AM fungi affect plant responses to root herbivores. This study aimed to investigate how AM fungi affect plant tolerance mechanisms to belowground herbivory. Methods We examined how AM fungi affect plant (Saccharum spp. hybrid) growth, nutrient dynamics and secondary chemistry (phenolics) in response to attack from a root-feeding insect (Dermolepida albohirtum). Results Root herbivory reduced root mass by almost 27%. In response, plants augmented investment in aboveground biomass by 25%, as well as increasing carbon concentrations. The AM fungi increased aboveground biomass, phosphorus and carbon. Meanwhile, root herbivory increased foliar phenolics by 31% in mycorrhizal plants, and increased arbuscular colonisation of roots by 75% overall. AM fungi also decreased herbivore performance, potentially via increasing root silicon concentrations. Conclusions Our results suggest that AM fungi may be able to augment plant tolerance to root herbivory via resource allocation aboveground and, at the same time, enhance plant root resistance by increasing root silicon. The ability of AM fungi to facilitate resource allocation aboveground in this way may be a more widespread strategy for plants to cope with belowground herbivory.

    更新日期:2020-01-04
  • Mycorrhizal and rhizospheric fungal community assembly differs during subalpine forest restoration on the eastern Qinghai-Tibetan Plateau
    Plant Soil (IF 3.259) Pub Date : 2019-12-17
    Gexi Xu, Huanhuan Chen, Zuomin Shi, Shun Liu, Xiangwen Cao, Miaomiao Zhang, Miao Chen, Jian Chen, Kai Xiong, Hongguo Yang, Guangdong Zhao

    Abstract Background and aims Mycorrhizosphere is the interface between roots and soil where a myriad of microorganisms mediate plant growth, nutrient acquisition and tolerance to biotic and abiotic stress, and result in driving ecosystem biogeochemical cycling. Understanding the complexity and dynamics of mycorrhizosphere and its ecology and evolution are critical to enhancing forest productivity and ecosystem functioning, especially in high latitude temperate or high altitude alpine forests. However, the fungal community compositions and their driving ecological mechanisms of mycorrhizosphere during forest restoration are poorly documented. Methods In this study, we simultaneously examined the ectomycorrhizal (EM) and rhizospheric fungal communities of two dominant host tree species (Abies faxoniana and Betula albosinensis) in subalpine forest communities with distinct forest restoration stages (30- vs. 60-year) after clear-cutting. Illumina MiSeq sequencing of internal transcribed spacer 2 (ITS2) sequences was adopted. Results A total of 1222 EM and 5880 rhizosphere fungal operational taxonomic units (OTUs) were obtained at a 97% sequence similarity level, which were mainly dominated by Basidiomycota. Host identity and forest restoration stage had no significant effects on fungal species richness of both EM and rhizospheric fungi. However, the community assembly of EM and rhizospheric fungi was significantly different during forest restoration, with opposite patterns shown on ectomycorrhizae and rhizosphere. The EM fungal community assembly was significantly affected by host identity, stand age and population dynamic, while the rhizosphere fungal community was significantly structured by combinations of host trees biomass, soil properties and spatial distance. Conclusions Our data provide important insights that community assembly of EM and rhizosphere fungi may respond idiosyncratically during forest restoration, which will help us deeper understanding forest succession, stability and ecosystem functioning on the Qinghai-Tibetan Plateau.

    更新日期:2020-01-04
  • Chemotaxis of Bacillus cereus YL6 and its colonization of Chinese cabbage seedlings
    Plant Soil (IF 3.259) Pub Date : 2019-12-17
    Xuefei Wang, Huiqin Xie, Yongli Ku, Xiangna Yang, Yinglong Chen, Nan Yang, Xueli Mei, Cuiling Cao

    Abstract Background and aims Phosphorus-solubilizing bacteria can colonize the surface of plant roots under natural conditions and may enter plant tissues to form endophytic symbiosis. They can convert unavailable phosphorus in the soil into available phosphorus, which can be utilized by plants. The aims of this study were to investigate the chemotaxis of Bacillus cereus YL6 and its migration and colonization sites in Chinese cabbage and to provide some technical support for the subsequent investigation of the physiological regulation mechanism of phosphate-dissolving bacteria in plants. Methods This study demonstrated that the green fluorescent protein marker did not affect the physiological and biochemical properties of YL6. Through the chemotaxis test and pot experiment, the colonization and growth promoting mechanism of YL6 in Chinese cabbage was explored. Results YL6 showed a strong positive chemotactic response to cabbage roots. The addition of organic acids to the soil promotes the colonization of YL6 in Chinese cabbage roots. Colonization of YL6 in Chinese cabbage is a dynamic process that moves from the root surface to root tissues and then up to stems and leaves. Fluorescence microscopy showed that YL6 mainly colonized cortical cells and vascular bundles of various plant tissues and was also observed in mesophyll cells. The proliferative effect of YL6 resulted from the interaction of effective phosphorus, and exuded auxin and gibberellin in the rhizosheath. Conclusion This study enhanced our understanding of the interaction mechanisms between phosphate-dissolving bacteria YL6 and Chinese cabbage. YL6 has the potential for future development into bio-fertilizer for agricultural production.

    更新日期:2020-01-04
  • Short-term yak-grazing alters plant-soil stoichiometric relations in an alpine meadow on the eastern Tibetan Plateau
    Plant Soil (IF 3.259) Pub Date : 2019-12-17
    Tserang Donko Mipam, Shiyong Chen, Jianquan Liu, Georg Miehe, Liming Tian

    Over-grazing have significantly altered above- and belowground functions in terrestrial ecosystem. However, the influence of grazing intensity on plant-soil stoichiometric relations in alpine ecosystems remains unclear.

    更新日期:2020-01-04
  • The multi-element stoichiometry of wet eucalypt forest is transformed by recent, frequent fire
    Plant Soil (IF 3.259) Pub Date : 2019-12-17
    Orpheus M. Butler, James J. Elser, Tom Lewis, Sarah C. Maunsell, Mehran Rezaei Rashti, Chengrong Chen

    Abstract Background and aims Fires can alter the elemental stoichiometry of ecosystems, reflecting altered patterns of biogeochemical cycling in the post-fire environment. However, elements other than carbon (C), nitrogen (N), and phosphorus (P) have rarely been studied in this context. Thus, we aimed to expand the understanding of fire’s stoichiometric and biogeochemical effects to encompass a broader suite of biogenic elements. Methods We compared the stoichiometric ratios of C, N, P, potassium (K), sodium (Na), magnesium (Mg), and sulfur (S) in soil, plant litter, and beetles (Thalycrodes pulchrum) between forest plots that have been burned biennially at low intensity since 1972 and plots that have remained unburned. Results Multi-element stoichiometry differed strongly between the fire regimes. Low intensity biennial burning was associated with depletion of C, N, and S relative to P, K, and to a small extent Mg and Na, in soil and litter. The stoichiometry of T. pulchrum biomass was not significantly affected by fire regime, but fire regime-associated variation in the stoichiometry of T. pulchrum biomass was positively correlated with the fire-induced stoichiometric shifts in soil. Conclusions The effects of low intensity prescribed fire on ecological stoichiometry extend to Na, K, Mg, and S in ways consistent with the respective potentials of these elements to volatilize during fire or accumulate in the absence of fire. These effects vary among ecosystem components in a manner that reveals the importance of biological processes and constraints as factors that determine the nature, magnitude, and potential consequences of the stoichiometric signatures of fire regimes. We conclude that long-term changes in fire regime can disrupt or even decouple the biogeochemical cycles of numerous biogenic elements in the soil–plant system.

    更新日期:2020-01-04
  • Effects of elevated atmospheric CO 2 on leaf gas exchange response to progressive drought in barley and tomato plants with different endogenous ABA levels
    Plant Soil (IF 3.259) Pub Date : 2019-12-17
    Zhenhua Wei, Liang Fang, Xiangnan Li, Jie Liu, Fulai Liu

    ABA plays an important role in modulating stomatal response to drought and elevated atmospheric CO2 (e [CO2]). This study aimed to investigate the effect of e[CO2] on the response of leaf gas exchange and plant water relations of barley and tomato plants with different endogenous ABA levels to progressive soil drying.

    更新日期:2020-01-04
  • Distinguishing the effects of vegetation restoration on runoff and sediment generation on simulated rainfall on the hillslopes of the loess plateau of China
    Plant Soil (IF 3.259) Pub Date : 2019-12-16
    Chaojun Gu, Xingmin Mu, Peng Gao, Guangju Zhao, Wenyi Sun, Xuejin Tan

    Since the 1970s, extensive croplands were converted to forest and pasture lands to control severe soil erosion on the Loess Plateau of China. We quantify the direct and indirect effects of vegetation restoration on runoff and sediment yield on hillslopes in the field to improve environmental governance.

    更新日期:2020-01-04
  • Bacteria and fungi differentially contribute to carbon and nitrogen cycles during biological soil crust succession in arid ecosystems
    Plant Soil (IF 3.259) Pub Date : 2019-12-14
    Lina Zhao, Yubing Liu, Zengru Wang, Shiwei Yuan, Jinghua Qi, Wenli Zhang, Yansong Wang, Xinrong Li

    Biological soil crusts (BSCs) are widely considered critical for soil fertility in arid ecosystems. However, how microbial communities regulate the C and N cycles during BSC succession is not well understood.

    更新日期:2020-01-04
  • Carbon storage change and δ 13 C transitions of peat columns in a partially forestry-drained boreal bog
    Plant Soil (IF 3.259) Pub Date : 2019-12-14
    Hannu Nykänen, Antti J. Rissanen, Jukka Turunen, Teemu Tahvanainen, Heikki Simola

    In forestry-drained peatlands, drying leads to changes in C cycling which could affect peat δ13C. Furthermore, the δ13C profile of the entire peat column may reveal effects of earlier climatic periods.

    更新日期:2020-01-04
  • Soil respiration in an irrigated oasis agroecosystem: linking environmental controls with plant activities on hourly, daily and monthly timescales
    Plant Soil (IF 3.259) Pub Date : 2019-12-14
    Ting Ma, Gaofeng Zhu, Jinzhu Ma, Kun Zhang, Shangtao Wang, Tuo Han, Shasha Shang

    Abstract Aim To investigate the responses of different components of soil respiration to environmental factors at different timescales in a vineyard ecosystem. Methods The trenching method was used to separate total soil respiration (TSR) into autotrophic respiration (AR) and heterotrophic respiration (HR). Soil respiration rates were measured by an LI-8100 automated flux system. Results On the hourly scale, there were contrasting responses in TSR, HR and AR to soil temperature at 5 cm (ST5), with clockwise hysteresis loop responses of TSR and HR to ST5 but a counterclockwise hysteresis loop between AR and ST5. The daily TSR didn’t exponentially response to ST5 during the growing season. On the monthly scale, the relationship between TSR and ST5 showed a counterclockwise hysteresis loop. Meanwhile, the diel respiration peak lagged the peak of gross primary productivity (GPP), but the monthly peak of TSR preceded the monthly peak of GPP. The daily TSR and the daily soil water content at 5 cm (SWC5) in different months showed a quadratic relationship, but there was an exponential correlation between the monthly TSR and the monthly SWC5. Conclusions The relationship between soil respiration and environmental factors derived for a specific timescale cannot be directly applied to other timescales.

    更新日期:2020-01-04
  • Nitrification in a zeoponic substrate.
    Plant Soil (IF 3.259) Pub Date : 2003-12-11
    R L McGilloway,R W Weaver,D W Ming,J E Gruener

    Clinoptilolite is a zeolite mineral with high cation exchange capacity used in zeoponic substrates that have been proposed as a solid medium for growing plants or as a fertilizer material. The kinetics of nitrification has not been measured for NH4+ saturated zeoponic substrate. Experiments were conducted to evaluate the production of NO2- and NO3-, and nitrifier populations in zeoponic substrates. Small columns were filled with zeoponic substrate inoculated with a commercial inoculum or soil enrichment culture of nitrifying bacteria. In addition to column studies, a growth chamber study was conducted to evaluate the kinetics of nitrification in zeoponic substrates used to grow radishes (Raphanus sativus L.). The zeoponic substrate provided a readily available source of NH4+, and nitrifying bacteria were active in the substrate. Ammonium oxidation rates in column studies ranged from 5 to 10 micrograms N g-1 substrate h-1, and NO2- oxidation rates were 2 to 9.5 micrograms N g-1 substrate h-1. Rates determined from the growth chamber study were approximately 1.2 micrograms N g-1 substrate h-1. Quantities of NH4+ oxidized to NO2- and NO3- in inoculated zeoponic substrate were in excess of plant up-take. Acidification as a result of NH4+ oxidation resulted in a pH decline, and the zeoponic substrate showed limited buffering capacity.

    更新日期:2019-11-01
  • Growth and cell wall changes in rice roots during spaceflight.
    Plant Soil (IF 3.259) Pub Date : 2003-11-25
    Takayuki Hoson,Kouichi Soga,Kazuyuki Wakabayashi,Seiichiro Kamisaka,Eiichi Tanimoto

    We analyzed the changes in growth and cell wall properties of roots of rice (Oryza sativa L. cv. Koshihikari) grown for 68.5, 91.5, and 136 h during the Space Shuttle STS-95 mission. In space, most of rice roots elongated in a direction forming a constant mean angle of about 55 degrees with the perpendicular base line away from the caryopsis in the early phase of growth, but later the roots grew in various directions, including away from the agar medium. In space, elongation growth of roots was stimulated. On the other hand, some of elasticity moduli and viscosity coefficients were higher in roots grown in space than on the ground, suggesting that the cell wall of space-grown roots has a lower capacity to expand than the controls. The levels of both cellulose and the matrix polysaccharides per unit length of roots decreased greatly, whereas the ratio of the high molecular mass polysaccharides in the hemicellulose fraction increased in space-grown roots. The prominent thinning of the cell wall could overwhelm the disadvantageous changes in the cell wall mechanical properties, leading to the stimulation of elongation growth in rice roots in space. Thus, growth and the cell wall properties of rice roots were strongly modified under microgravity conditions during spaceflight.

    更新日期:2019-11-01
  • Iodate and iodide effects on iodine uptake and partitioning in rice (Oryza sativa L.) grown in solution culture.
    Plant Soil (IF 3.259) Pub Date : 2002-01-05
    C L Mackowiak,P R Grossl

    In the Xinjiang province of western China, conventional methods of iodine (I) supplementation (i.e, goiter pills and iodinated salt) used to mitigate I deficiencies were ineffectual. However, the recent addition of KIO3 to irrigation waters has proven effective. This study was conducted to determine the effects of I form and concentration on rice (Oryza sativa L.) growth, I partitioning within the plant, and ultimately to assist in establishing guidelines for incorporating I into the human food chain. We compared IO3- vs. I- in order to determine how these chemical species differ in their biological effects. Rice was grown in 48 L aerated tubs containing nutrient solution and IO3- or I- at 0, 1, 10, or 100 micromoles concentrations (approximately 0, 0.1, 1, and 10 mg kg-1 I). The IO3- at 1 and 10 micromoles had no effect on biomass yields, and the 100 micromole treatment had a small negative effect. The I- at 10 and 100 micromoles was detrimental to biomass yields. The IO3- treatments had more I partitioning to the roots (56%) on average than did the I- treatments (36%), suggesting differences in uptake or translocation between I forms. The data support the theory that IO3- is electrochemically or biologically reduced to I- prior to plant uptake. None of the treatments provided sufficient I in the seed to meet human dietary requirements. The I concentration found in straw at 100 micromoles IO3- was several times greater than seed, and could provide an indirect source of dietary I via livestock feeding on the straw.

    更新日期:2019-11-01
  • The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model.
    Plant Soil (IF 3.259) Pub Date : 2001-09-07
    Z Ge,G Rubio,J P Lynch

    We have observed that low soil phosphorus availability alters the gravitropic response of basal roots in common bean (Phaseolus vulgaris L.), resulting in a shallower root system. In this study we use a geometric model to test the hypotheses that a shallower root system is a positive adaptive response to low soil P availability by (1) concentrating root foraging in surface soil horizons, which generally have the highest P availability, and (2) reducing spatial competition for P among roots of the same plant. The growth of nine root systems contrasting in gravitropic response over 320 h was simulated in SimRoot, a dynamic three-dimensional geometric model of root growth and architecture. Phosphorus acquisition and inter-root competition were estimated with Depzone, a program that dynamically models nutrient diffusion to roots. Shallower root systems had greater P acquisition per unit carbon cost than deeper root systems, especially in older root systems. This was due to greater inter-root competition in deeper root systems, as measured by the volume of overlapping P depletion zones. Inter-root competition for P was a significant fraction of total soil P depletion, and increased with increasing values of the P diffusion coefficient (De), with root age, and with increasing root gravitropism. In heterogenous soil having greater P availability in surface horizons, shallower root systems had greater P acquisition than deeper root systems, because of less inter-root competition as well as increased root foraging in the topsoil. Root P acquisition predicted by SimRoot was validated against values for bean P uptake in the field, with an r2 between observed and predicted values of 0.75. Our results support the hypothesis that altered gravitropic sensitivity in P-stressed roots, resulting in a shallower root system, is a positive adaptive response to low P availability by reducing inter-root competition within the same plant and by concentrating root activity in soil domains with the greatest P availability.

    更新日期:2019-11-01
  • Environmental differences between sites control the diet and nutrition of the carnivorous plant Drosera rotundifolia.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Joni L Cook,J Newton,J Millett

    Background and aims Carnivorous plants are sensitive to small changes in resource availability, but few previous studies have examined how differences in nutrient and prey availability affect investment in and the benefit of carnivory. We studied the impact of site-level differences in resource availability on ecophysiological traits of carnivory for Drosera rotundifolia L. Methods We measured prey availability, investment in carnivory (leaf stickiness), prey capture and diet of plants growing in two bogs with differences in N deposition and plant available N: Cors Fochno (0.62 g m-2 yr.-1, 353 μg l-1), Whixall Moss (1.37 g m-2 yr.-1, 1505 μg l-1). The total N amount per plant and the contributions of prey/root N to the plants' N budget were calculated using a single isotope natural abundance method. Results Plants at Whixall Moss invested less in carnivory, were less likely to capture prey, and were less reliant on prey-derived N (25.5% compared with 49.4%). Actual prey capture did not differ between sites. Diet composition differed - Cors Fochno plants captured 62% greater proportions of Diptera. Conclusions Our results show site-level differences in plant diet and nutrition consistent with differences in resource availability. Similarity in actual prey capture may be explained by differences in leaf stickiness and prey abundance.

    更新日期:2019-11-01
  • Molecular dynamics in germinating, endophyte-colonized quinoa seeds.
    Plant Soil (IF 3.259) Pub Date : 2018-02-09
    Andrea Pitzschke

    Aims The pseudo-cereal quinoa has an outstanding nutritional value. Seed germination is unusually fast, and plant tolerance to salt stress exceptionally high. Seemingly all seeds harbor bacterial endophytes. This work examines mitogen-activated protein kinase (MAPK) activities during early development. It evaluates possible contribution of endophytes to rapid germination and plant robustness. Methods MAPK activities were monitored in water- and NaCl-imbibed seeds over a 4-h-period using an immunoblot-based approach. Cellulolytic and pectinolytic abilities of bacteria were assessed biochemically, and cellular movement, biofilm, elicitor and antimicrobial compound synthesis genes sequenced. GyrA-based, cultivation-independent studies provided first insight into endophyte diversity. Results Quinoa seeds and seedlings exhibit remarkably complex and dynamic MAPK activity profiles. Depending on seed origin, variances exist in MAPK patterns and probably also in endophyte assemblages. Mucilage-degrading activities enable endophytes to colonize seed surfaces of a non-host species, chia, without apparent adverse effects. Conclusions Owing to their motility, cell wall-loosening and elicitor-generating abilities, quinoa endophytes have the potential to drive cell expansion, move across cell walls, generate damage-associated molecular patterns and activate MAPKs in their host. Bacteria may thus facilitate rapid germination and confer a primed state directly upon seed rehydration. Transfer into non-native crops appears both desirable and feasible.

    更新日期:2019-11-01
  • Intensive ground vegetation growth mitigates the carbon loss after forest disturbance.
    Plant Soil (IF 3.259) Pub Date : 2017-12-12
    Bernhard Zehetgruber,Johannes Kobler,Thomas Dirnböck,Robert Jandl,Rupert Seidl,Andreas Schindlbacher

    Aims Slow or failed tree regeneration after forest disturbance is increasingly observed in the central European Alps, potentially amplifying the carbon (C) loss from disturbance. We aimed at quantifying C dynamics of a poorly regenerating disturbance site with a special focus on the role of non-woody ground vegetation. Methods Soil CO2 efflux, fine root biomass, ground vegetation biomass, tree increment and litter input were assessed in (i) an undisturbed section of a ~ 110 years old Norway spruce stand, (ii) in a disturbed section which was clear-cut six years ago (no tree regeneration), and (iii) in a disturbed section which was clear-cut three years ago (no tree regeneration). Results Total soil CO2 efflux was similar across all stand sections (8.5 ± 0.2 to 8.9 ± 0.3 t C ha-1 yr.-1). The undisturbed forest served as atmospheric C sink (2.1 t C ha-1 yr.-1), whereas both clearings were C sources to the atmosphere. The source strength three years after disturbance (-5.5 t C ha-1 yr.-1) was almost twice as high as six years after disturbance (-2.9 t C ha-1 yr.-1), with declining heterotrophic soil respiration and the high productivity of dense graminoid ground vegetation mitigating C loss. Conclusions C loss after disturbance decreases with time and ground vegetation growth. Dense non-woody ground vegetation cover can hamper tree regeneration but simultaneously decrease the ecosystem C loss. The role of ground vegetation should be more explicitly taken into account in forest C budgets assessing disturbance effects.

    更新日期:2019-11-01
  • The effect of pH, electrolytes and temperature on the rhizosphere geochemistry of phytosiderophores.
    Plant Soil (IF 3.259) Pub Date : 2017-10-11
    M Walter,S M Kraemer,W D C Schenkeveld

    BACKGROUND AND AIMS Graminaceous plants are grown worldwide as staple crops under a variety of climatic and soil conditions. They release phytosiderophores for Fe acquisition (Strategy II). Aim of the present study was to uncover how the rhizosphere pH, background electrolyte and temperature affect the mobilization of Fe and other metals from soil by phytosiderophores. METHODS For this purpose a series of kinetic batch interaction experiments with the phytosiderophore 2'-deoxymugineic acid (DMA), a calcareous clay soil and a mildly acidic sandy soil were performed. The temperature, electrolyte concentration and applied electrolyte cation were varied. The effect of pH was examined by applying two levels of lime and Cu to the acidic soil. RESULTS Fe mobilization by DMA increased by lime application, and was negatively affected by Cu amendment. Mobilization of Fe and other metals decreased with increasing ionic strength, and was lower for divalent than for monovalent electrolyte cations at equal ionic strength, due to higher adsorption of metal-DMA complexes to the soil. Metal mobilization rates increased with increasing temperature leading to a faster onset of competition; Fe was mobilized faster, but also became depleted faster at higher temperature. Temperature also affected biodegradation rates of metal-DMA complexes. CONCLUSION Rhizosphere pH, electrolyte type and concentration and temperature can have a pronounced effect on Strategy II Fe acquisition by affecting the time and concentration 'window of Fe uptake' in which plants can benefit from phytosiderophore-mediated Fe uptake.

    更新日期:2019-11-01
  • Differential elemental uptake in three pseudo-metallophyte C4 grasses in situ in the eastern USA.
    Plant Soil (IF 3.259) Pub Date : 2017-08-29
    Cédric Gonneau,Sanjay K Mohanty,Lee H Dietterich,Wei-Ting Hwang,Jane K Willenbring,Brenda B Casper

    BACKGROUND AND AIMS Elemental uptake in serpentine floras in eastern North America is largely unknown. The objective of this study was to determine major and trace element concentrations in soil and leaves of three native pseudo-metallophyte C4 grasses in situ at five sites with three very different soil types, including three serpentine sites, in eastern USA. METHODS Pseudo-total and extractible concentrations of 15 elements were measured and correlated from the soils and leaves of three species at the five sites. RESULTS Element concentrations in soils of pseudo-metallophytes varied up to five orders of magnitude. Soils from metalliferous sites exhibited higher concentrations of their characteristic elements than non-metalliferous. In metallicolous populations, elemental concentrations depended on the element. Concentrations of major elements (Ca, Mg, K) in leaves were lower than typical toxicity thresholds, whereas concentrations of Zn were higher. CONCLUSIONS In grasses, species can maintain relatively low metal concentrations in their leaves even when soil concentrations are richer. However, in highly Zn-contaminated soil, we found evidence of a threshold concentration above which Zn uptake increases drastically. Finally, absence of main characteristics of serpentine soil at one site indicated the importance of soil survey and restoration to maintain serpentinophytes communities and avoid soil encroachment.

    更新日期:2019-11-01
  • Mycorrhizas and soil ecosystem function of co-existing woody vegetation islands at the alpine tree line.
    Plant Soil (IF 3.259) Pub Date : 2017-02-22
    Lixia Wang,Burenjargal Otgonsuren,Douglas L Godbold

    BACKGROUND AND AIMS Picea abies, Pinus mugo and Rhododendron ferrugineum co-exist at the alpine tree line, and can have different mycorrhizal communities. The activity and diversity of mycorrhizal fungi are considered to be important factors in regulation of soil function. METHODS At a tree line site and a lower elevation site in the Austrian Alps, the community structure of ectomycorrhiza on Picea abies and Pinus mugo was determined. The activity of surface enzymes was determined on ectomycorrhizal and ericoid mycorrhizal roots. In soils, the activity of a range of enzymes, nitrogen (N) mineralization and biomass decomposition were determined. RESULTS The community structure of the ectomycorrhizal community of Picea abies and Pinus mugo differed strongly, but the average activity of surface enzymes of the ectomycorrhizal communities was similar. A lower root surface enzyme activity was determined on Rhododendron ferrugineum. Soil N-mineralization under Rhododendron ferrugineum was significantly lower than under Picea abies and Pinus mugo. In soil, the activity of a range of enzymes did not differ at the tree line but differed between the tree line and the lower elevation sites. CONCLUSION The different ectomycorrhizal communities on Picea abies and Pinus mugo and ericoid mycorrhizas on Rhododendron ferrugineum support similar ecosystem functions in soil.

    更新日期:2019-11-01
  • Mutualism between Klebsiella SGM 81 and Dianthus caryophyllus in modulating root plasticity and rhizospheric bacterial density.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Shraddha Gang,Meenu Saraf,Christopher J Waite,Martin Buck,Jörg Schumacher

    Aims Dianthus caryophyllus is a commercially important ornamental flower. Plant growth promoting rhizobacteria are increasingly applied as bio-fertilisers and bio-fortifiers. We studied the effect of a rhizospheric isolate Klebsiella SGM 81 strain to promote D. caryophyllus growth under sterile and non-sterile conditions, to colonise its root system endophytically and its impact on the cultivatable microbial community. We identified the auxin indole-3-acetic acid (IAA) production of Klebsiella SGM 81 as major bacterial trait most likely to enhance growth of D. caryophyllus. Methods ipdC dependent IAA production of SGM 81 was quantified using LC-MS/MS and localised proximal to D. caryophyllus roots and correlated to root growth promotion and characteristic morphological changes. SGM 81 cells were localised on and within the plant root using 3D rendering confocal microscopy of gfp expressing SGM 81. Using Salkowski reagent IAA production was quantified and localised proximal to roots in situ. The effect of different bacterial titres on rhizosphere bacterial population was CFU enumerated on nutrient agar. The genome sequence of Klebsiella SGM 81 (accession number PRJEB21197) was determined to validate PGP traits and phylogenic relationships. Results Inoculation of D. caryophyllus roots with Klebsiella SGM 81 drastically promoted plant growth when grown in agar and soil, concomitant with a burst in root hair formation, suggesting an increase in root auxin activity. We sequenced the Klebsiella SGM 81 genome, identified the presence of a canonical ipdC gene in Klebsiella SGM 81, confirmed bacterial production and secretion of IAA in batch culture using LC-MS/MS and localised plant dependent IAA production by SGM 81 proximal to roots. We found Klebsiella SGM 81 to be a rhizoplane and endophytic coloniser of D. caryophyllus roots in a dose dependent manner. We found no adverse effects of SGM 81 on the overall rhizospheric microbial population unless supplied to soil in very high titres. Conclusion Klebsiella SGM 81 effectively improves root traits of D. caryophyllus in a dose dependent manner, likely through tryptophan dependent IAA production in the rhizoplane and potentially within the intercellular spaces of root tissue. Under optimal plant growth promoting conditions in non-sterile soil, the high total microbial titre in the rhizosphere supports a mutualistic relationship between Klebsiella SGM 81 and carnation that potentially extends to the wider rhizosphere microbiota.

    更新日期:2019-11-01
  • Depth of soil compaction predominantly affects rice yield reduction by reproductive-stage drought at varietal screening sites in Bangladesh, India, and Nepal.
    Plant Soil (IF 3.259) Pub Date : 2017-01-01
    Suresh Prasad Singh,Abhinav Jain,M S Anantha,Santosh Tripathi,Subarna Sharma,Santosh Kumar,Archana Prasad,Bhawana Sharma,Biswajit Karmakar,Rudra Bhattarai,Sankar Prasad Das,Shravan K Singh,Vinay Shenoy,R Chandra Babu,S Robin,Padmini Swain,J L Dwivedi,Ram Baran Yadaw,Nimai P Mandal,T Ram,Krishna Kumar Mishra,S B Verulkar,Tamal Aditya,Krishna Prasad,Puvvada Perraju,Ram Krishna Mahato,Sheetal Sharma,K Anitha Raman,Arvind Kumar,Amelia Henry

    Aims Drought is the major constraint to rainfed rice productivity in South Asia, but few reports provide detailed characterization of the soil properties related to drought stress severity in the region. The aim of the study was to provide a compilation of drought breeding network sites and their respective levels of drought stress, and to relate soil parameters with yield reduction by drought. Methods This study characterized levels of drought stress and soil nutrient and physical properties at 18 geographically distributed research station sites involved in rice varietal screening in Bangladesh, India, and Nepal, as well as at farmers' fields located near the research stations. Results Based on soil resistance to penetration profiles, a hardpan was surprisingly absent at about half of the sites characterized. Significant relationships of depth of compaction and yield reduction by drought indicated the effects of soil puddling on susceptibility to cracking, rather than water retention by hardpans, on plant water availability in this region. The main difference between research stations and nearby farmers' fields was in terms of soil compaction. Conclusions These results present an initiative for understanding the range of severities of reproductive-stage drought stress in drought-prone rainfed lowland rice-growing areas in South Asia.

    更新日期:2019-11-01
  • Plant-soil interactions in Mediterranean forest and shrublands: impacts of climatic change.
    Plant Soil (IF 3.259) Pub Date : 2013-04-01
    J Sardans,J Peñuelas

    Background In the Mediterranean climate, plants have evolved under conditions of low soil-water and nutrient availabilities and have acquired a series of adaptive traits that, in turn exert strong feedback on soil fertility, structure, and protection. As a result, plant-soil systems constitute complex interactive webs where these adaptive traits allow plants to maximize the use of scarce resources. Scope It is necessary to review the current bibliography to highlight the most know characteristic mechanisms underlying Mediterranean plant-soil feed-backs and identify the processes that merit further research in order to reach an understanding of the plant-soil feed-backs and its capacity to cope with future global change scenarios. In this review, we characterize the functional and structural plant-soil relationships and feedbacks in Mediterranean regions. We thereafter discuss the effects of global change drivers on these complex interactions between plants and soil. Conclusions The large plant diversity that characterizes Mediterranean ecosystems is associated to the success of coexisting species in avoiding competition for soil resources by differential exploitation in space (soil layers) and time (year and daily). Among plant and soil traits, high foliar nutrient re-translocation and large contents of recalcitrant compounds reduce nutrient cycling. Meanwhile increased allocation of resources to roots and soil enzymes help to protect against soil erosion and to improve soil fertility and capacity to retain water. The long-term evolutionary adaptation to drought of Mediterranean plants allows them to cope with moderate increases of drought without significant losses of production and survival in some species. However, other species have proved to be more sensitive decreasing their growth and increasing their mortality under moderate rising of drought. All these increases contribute to species composition shifts. Moreover, in more xeric sites, the desertification resulting from synergic interactions among some related process such as drought increases, torrential rainfall increases and human driven disturbances is an increasing concern. A research priority now is to discern the effects of long-term increases in atmospheric CO2 concentrations, warming, and drought on soil fertility and water availability and on the structure of soil communities (e.g. shifts from bacteria to fungi) and on patching vegetation and root-water uplift (from soil to plant and from soil deep layers to soil superficial layers) roles in desertification.

    更新日期:2019-11-01
  • Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis.
    Plant Soil (IF 3.259) Pub Date : 2019-04-23
    M Naveed,M A Ahmed,P Benard,L K Brown,T S George,A G Bengough,T Roose,N Koebernick,P D Hallett

    Aims Rhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin. Methods Surface tension and viscosity of the exudate solutions were measured using the Du Noüy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6 mg g-1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential. Results Surface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at -1500 kPa matric potential. Conclusions Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.

    更新日期:2019-11-01
  • Density-dependency and plant-soil feedback: former plant abundance influences competitive interactions between two grassland plant species through plant-soil feedbacks.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Wei Xue,T Martijn Bezemer,Frank Berendse

    Backgrounds and aims Negative plant-soil feedbacks (PSFs) are thought to promote species coexistence, but most evidence is derived from theoretical models and data from plant monoculture experiments. Methods We grew Anthoxanthum odoratum and Centaurea jacea in field plots in monocultures and in mixtures with three ratios (3:1, 2:2 and 1:3) for three years. We then tested in a greenhouse experiment the performance of A. odoratum and C. jacea in pots planted with monocultures and 1:1 mixtures and filled with live and sterile soils collected from the field plots. Results In the greenhouse experiment, C. jacea produced less aboveground biomass in soil conditioned by C. jacea monocultures than in soil conditioned by A. odoratum monocultures, while the aboveground biomass of A. odoratum in general did not differ between the two monospecific soils. The negative PSF effect was greater in the 1:1 plant mixture than in plant monocultures for A. odoratum but did not differ for C. jacea. In the greenhouse experiment, the performance of C. jacea relative to A. odoratum in the 1:1 plant mixture was negatively correlated to the abundance of C. jacea in the field plot where the soil was collected from. This relationship was significant both in live and sterile soils. However, there was no relationship between the performance of A. odoratum relative to C. jacea in the 1:1 plant mixture in the greenhouse experiment and the abundance of A. odoratum in the field plots. Conclusions The response of a plant to PSF depends on whether the focal species grows in monocultures or in mixtures and on the identity of the species. Interspecific competition can exacerbate the negative plant-soil feedbacks compared to intraspecific competition when a plant competes with a stronger interspecific competitor. Moreover, the abundance of a species in mixed plant communities, via plant-soil feedback, negatively influences the relative competitiveness of that species when it grows later in interspecific competition, but this effect varies between species. This phenomenon may contribute to the coexistence of competing plants under natural conditions through preventing the dominance of a particular plant species.

    更新日期:2019-11-01
  • Spatial heterogeneity in root litter and soil legacies differentially affect legume root traits.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Sirgi Saar,Marina Semchenko,Janna M Barel,Gerlinde B De Deyn

    Background and Aims Plants affect the soil environment via litter inputs and changes in biotic communities, which feed back to subsequent plant growth. Here we investigated the individual contributions of litter and biotic communities to soil feedback effects, and plant ability to respond to spatial heterogeneity in soil legacy. Methods We tested for localised and systemic responses of Trifolium repens to soil biotic and root litter legacy of seven grassland species by exposing half of a root system to control soil and the other half to specific inoculum or root litter. Results Soil inoculation triggered a localised reduction in root length while litter locally increased root biomass independent of inoculum or litter species identity. Nodule formation was locally suppressed in response to soil conditioned by another legume (Vicia cracca) and showed a trend towards systemic reduction in response to conspecific soil. V. cracca litter also caused a systemic response with thinner roots produced in the part of the root system not directly exposed to the litter. Conclusions Spatial heterogeneity in root litter distribution and soil communities generate distinct local and systemic responses in root morphology and nodulation. These responses can influence plant-mutualist interactions and nutrient cycling, and should be included in plant co-existence models.

    更新日期:2019-11-01
  • Genotypic differences in symbiotic nitrogen fixation ability and seed yield of climbing bean.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Norma Barbosa,Elizabeth Portilla,Hector Fabio Buendia,Bodo Raatz,Stephen Beebe,Idupulapati Rao

    Aims Symbiotic nitrogen fixation (SNF) contributes to improve grain yield under nitrogen (N) deficiency. Climbing beans are known to be superior to bush beans in their potential for SNF. The main objectives of this study were to: (i) quantify genotypic differences in SNF ability of climbing beans using 15N natural abundance method; (ii) identify climbing bean genotypes that combine high SNF ability with high yield potential that could serve as parents in the breeding program; and (iii) test whether δ15N in seed can be used instead of δ15N in shoot for estimating SNF ability. Methods 98 Climbing bean genotypes were evaluated for SNF ability in terms of nitrogen derived from the atmosphere (%Ndfa). Field trials were conducted at two locations in Colombia. Results Significant genotypic differences were observed in SNF ability. Good yielding lines with 4.6 t ha-1 fixed as much as 60% of their N (up to 92 kg of N fixed ha-1) without application of N fertilizer to soil. Conclusions Based on evaluations from both locations, seven climbing bean lines (ENF 235, ENF 234, ENF 28, ENF 21, MAC 27, CGA 10 and PO07AT49) were identified as promising genotypes. Seed samples can be used to determine SNF ability, to select for genotypes with superior SNF ability.

    更新日期:2019-11-01
  • A quantitative method for the high throughput screening for the soil adhesion properties of plant and microbial polysaccharides and exudates.
    Plant Soil (IF 3.259) Pub Date : 2018-01-01
    Jumana Akhtar,Andrew F Galloway,Georgios Nikolopoulos,Katie J Field,Paul Knox

    Background and aims Understanding the structures and functions of carbon-based molecules in soils is an important goal in the context of soils as an ecosystem function of immense importance. Polysaccharides are implicated in maintaining soil aggregate status but have not been extensively dissected in terms of their structures and soil adhesion properties. This is largely because of the technical difficulties in identifying polysaccharide structures and quantifying any functional properties. Methods Here, we describe the use of a novel nitrocellulose-based adhesion assay to determine the relative capacities for soil adhesion of over twenty plant and microbial polysaccharides that are likely to be present in soil and to contribute to organic matter content and properties. Weights of soil adhered to spots of known amounts of specific polysaccharides were quantified by scanning of the nitrocellulose sheets. Results The most effective polysaccharides identified from this survey included chitosan, β-1,3-glucan, gum tragacanth, xanthan and xyloglucan. We also demonstrate that the soil adhesion assay is suitable to assess the soil-binding properties of plant exudates. Conclusions The soil adhesion assay will be useful for the functional dissection of the organic matter components of soils and also of the factors involved in soil attachment to plant roots and in rhizosheath formation.

    更新日期:2019-11-01
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