Selenium nanoparticles reduced cadmium uptake, regulated nutritional homeostasis and antioxidative system in Coriandrum sativum grown in cadmium toxic conditions
Introduction
Heavy metal pollution is a deleterious stress disturbing growth of plants. Metal pollution severely deteriorates the food quality as well as the prevailing environment. The unrestricted growth of urban areas, rapid industrialization, frequent application of synthetic chemicals for crop production, inappropriate waste disposal, and irrational mining activities cause metal pollution (Rajput et al., 2021). Globally, more than 10 million areas are polluted and most of these areas are metal contaminated. The disposal of industrial wastes and application of phosphatic fertilizers in arable areas results in cadmium (Cd) pollution in the agricultural sites (Zaheer et al., 2018). Amongst several metal contaminants, Cd is the most injurious to growth and development of plants. Plant roots readily uptake Cd due to the higher mobility and hydrophilicity of this metal in rhizospheric area (Hussain et al., 2020). Most developing countries don't have ample amounts and sources of irrigation water. Hence, farmers of such countries apply industrial wastewater to irrigate their crop plants resulting in the enhancement of Cd pollution. Roots uptake Cd from growing media and then Cd is translocated to the upper edible portions of the plants. Consumption of Cd contaminated food results in numerous medical issues including malfunctioning of heart, liver, kidneys, and immune systems (Ismael et al., 2019). Cadmium affected plants exhibit reduced chlorophyll contents because this toxic metal reduces the uptake of macro and micro nutrients required for the appropriate functioning of photosynthetic apparatus. The reduced uptake of macro nutrients by Cd stressed plants impedes physiochemical activities causing inhibited growth of plants (Benáková et al., 2017). Moreover, higher levels of ROS, synthesized due to Cd stress, impose negative effects on oxidation/reduction, ionic absorption, respiration, photosynthetic activity and the hormonal homeostasis in plants (Berni et al., 2019).
Application of growth promoting microbes, phytohormones and plant nutrients alleviate Cd induced stress in plants (Shah et al., 2020). Some recent studies have demonstrated that selenium (Se) may mitigate various kinds of abiotic stresses in applied plants (Du et al., 2019). Selenoenzymes are antioxidants and selenite and selenate forms of Se are the basic constituent of these enzymes (Raymond et al., 2014). Selenite attached to the rhizospheric soil particles is available to plants while selenate leaches down and remains unavailable to plants (Fio et al., 1991). Selenium mainly uses sulfur (S) transport and the S metabolic pathway. Selenium aids in scavenging of free radicals and ROS through regulation of the antioxidative apparatuses in the applied plants (Cui et al., 2018). Detoxification of ROS through antioxidant machinery defends plants from oxidative injuries. Consequently, Se improves antioxidative defense machinery, membranous integrity which is considered as a major criterion for stress alleviation in plants (de Brito Mateus et al., 2021). Similarly, Se decreased Cd-bioaccumulation and MDA level, enhanced antioxidant activity, growth and grain production of supplemented wheat plants (Zhou et al., 2020).
Coriander is an important vegetable crop of Mediterranean region and Pakistan. The green leaves and seeds of coriander are widely used to flavor and garnish culinary-dishes besides extraction of essential oil (Deepa et al., 2020). Seeds and leaves of coriander are used to prepare cosmetics, food and traditional medicines. The elite characteristics of nanoparticles (NPs) may be utilized to improve seed germination and crop production. Recent studies have demonstrated that selenium nanoparticles (SeNPs) may improve nutrients uptake, growth and yield of applied plants (Gudkov et al., 2020; Li et al., 2020a, 2020b). Additionally, post emergence application of SeNPs alleviates drought and salinity stress in plants (Ikram et al., 2020; Zahedi et al., 2019). Coriander is a highly perishable crop and mostly cultivated in the agricultural sites present near urban areas. Farmers of these regions usually irrigate their crops by untreated drain water contaminated with industrial effluents. Cadmium is an important metal contaminant of these agricultural soils. Hence, it becomes necessary to evaluate the effect of Cd induced toxicity and search out the appropriate remedy for alleviation of respective stress in coriander. Though, there is no research work concerning the potential of SeNPs for mitigation of Cd stress in coriander. During the current study, it was postulated that seed priming with SeNPs may improve growth and physiochemical attributes in Coriandrum sativum grown in Cd-toxic soil.
Section snippets
Seed priming and growth conditions
Seeds of coriander (Coriandrum sativum L.) were sterilized by immersing in sodium hypochlorite solution (0.5%) for 3 min and then properly washed 3 times by using distilled water. Selenium nanoparticles (SeNPs), used during current study were acquired from the NanoSany Corporation, Iran. The spherical SeNPs had average particle size of 10–45 nm with 30–50 m2 g−1 specific surface area and 3.89 g cm−3 true density. Seeds were primed with SeNPs solution prepared by dissolving SeNPs in double
Evaluation of soil physicho-chemical features, plant growth attributes and biomass yield
The loamy soil used during present study included 0.61 g P kg−1, 0.5 g Zn kg−1, 2.5 g K kg−1, 1.4 g N kg−1, 3.9 g organic matter kg−1, besides 0.6 mg Cr kg−1 and 0.04 mg Ni kg−1 at 7.9 pH. Reduced seed germination (1.5 fold), poor root length (1.5 fold) along with shoot length (1.72 fold) was observed in coriander plants under Cd regimes (Table 1). The root length and shoot length augmented due to SeNPs supplementation, compared to control and Cd-affected plants. Escalation of SeNPs dosage (Se1
Discussion
Frequent industrialization and related human activities has increased the Cd contamination in agricultural soils. The Cd-induced toxicity drastically reduces growth, quality and development of crop plants growing in metal polluted areas. Cd-toxicity interrupts the germination of seed by upsetting the equilibrium of amino acids, nutrients and carbohydrates in cotyledon/embryo (Aihemaiti et al., 2018). During the current study, coriander seedlings exposed to Cd stress showed reduced growth, and
Conclusion
Our results unveiled that seed priming with SeNPs may become an effective tactic for crop production because it alleviates environmental stresses through improving antioxidative systems, diminishing oxidative injury, and increasing plant growth. This study exhibited the enormous potential of SeNPs to acquire sustainable crop production in Cd spiked soil. Generally, Cd toxicity severely decreased the growth of coriander plants. However, SeNPs alleviated Cd toxicity through enriching nutrition,
Credit author statement
SA and NAY gave the idea about the research work. RS conducted experiment and carried out statistical analysis. NAY contributed in writing manuscript. AAS reviewed and drafted the research work.
Declaration of competing interest
All authors declare that they have no conflict of interest.
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