Within this special issue of NZJA entitled ‘Advances in Plant Sciences’ we present a collection of papers which bring new science to the discipline of grassland plants. Of the 14 papers contained in this issue, 6 relate specifically to clovers and legumes, 3 to clovers and grasses, 3 to grasses and weeds and 2 to a forages. It is interesting and encouraging to note the dominance of grassland legume based studies in this issue. Although globally contemporary agriculture has a strong dependence on fertiliser nitrogen (N) for plant N nutrition, it appears that legumes still have a major importance in our grazed grasslands, both in terms of N inputs to the systems via N2 fixation, but also to the high quality feed value of the legumes for grazing farm animals. Subject matter in this issue covers a broad spectrum in the discipline of plant sciences. These include field comparisons of clover cultivars, Lucerne or clover/ grass mixes, rhizobia, germination requirements, plant metal tolerances, pasture/animal effects, root investigations, plant breeding, herbicide resistance and plant pests. There is currently substantial interest and work being conducted on grassland legumes, some of which is presented here. As a prominent work in this special issue, Moot et al. (2020) provide a substantial data set from a 5-year grazing trial comparing grazed Lucerne and Lucerne/grass mixes in New Zealand dryland. This work provides important quantification over the medium-term of Lucerne and grass mixes in terms of yield, sward composition and animal production response. As an annual clover species, subterranean clover plays a critical role in many grassland swards, particularly in environments with consistent severe summer dry conditions, where perennial clovers fail to persist. Subterranean clover is the focus of Teixeira et al. (2020a), who compare the thermal time requirements for germination of 4 key cultivars. The authors present important new information on temperature requirements these cultivars and concluded that late summer and autumn temperatures are ideal germination conditions. Teixeira et al. (2020b) also investigated the phenomena of ‘leaf reddening’ in sub clover in terms of causes, and plant impacts. They found that Leaf reddening was induced by cold temperatures, and importantly, did not affect subsequent plant growth. Nguyen et al. (2020) examined the rhizobia of the perennial Caucasian clover, under both ‘low’ and ‘high’ soil fertility conditions. Nodulation was studied at several field sites varying in age, and interestingly the authors found that the rhizobia specific to this legume has retained effectiveness for up to 42 years, regardless of soil fertility status. Soil aluminium (Al) concentrations have major impacts on grassland legumes where soils are acid. Some legumes appear to have specific root mechanisms to combat soil Al toxicity, but we have very little knowledge in this important field of research. Ma et al. (2020) contribute an interesting piece of work on this issue, focusing on Lucerne, an Al sensitive legume species, and the release of specific root exudates to potentially reduce the impacts of high soil aluminium. These researchers concluded that even Lucerne shows potential to develop mechanisms such as releasing organic acids from roots. On a different note, Young et al. (2020) studied cadmium

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植物科学进展

在本期名为“植物科学进展”的 NZJA 特刊中，我们展示了一系列论文，这些论文为草原植物学科带来了新的科学。在本期包含的 14 篇论文中，6 篇专门与三叶草和豆类有关，3 篇与三叶草和草有关，3 篇与草和杂草有关，2 篇与草料有关。在这个问题上注意到基于草原豆科植物的研究的主导地位是有趣和令人鼓舞的。尽管全球当代农业在植物氮营养方面强烈依赖化肥氮 (N)，但豆科植物似乎在我们放牧的草原中仍然具有重要意义，无论是通过 N2 固定向系统输入氮，还是豆类对于放牧农场动物的高品质饲料价值。本期主题涵盖植物科学学科的广泛领域。这些包括三叶草栽培品种、卢塞恩或三叶草/草混合物、根瘤菌、发芽要求、植物金属耐受性、牧场/动物效应、根系调查、植物育种、除草剂抗性和植物害虫的田间比较。目前，人们对草原豆科植物有着浓厚的兴趣并正在开展相关工作，此处介绍了其中一些。作为本期特刊中的一项突出工作，Moot 等人。(2020) 提供了来自一项为期 5 年的放牧试验的大量数据集，该试验比较了新西兰旱地放牧的琉森和琉森/草混合。这项工作在产量、草料组成和动物生产反应方面提供了中期琉森和草混合的重要量化。作为一年生三叶草物种，地下三叶草在许多草原草场中起着至关重要的作用，特别是在夏季持续严重干旱的环境中，多年生三叶草无法生存。地下三叶草是 Teixeira 等人的研究重点。(2020a)，他们比较了 4 个关键品种发芽的热时间要求。作者提供了有关这些品种的温度要求的重要新信息，并得出结论，夏末和秋季温度是理想的发芽条件。特谢拉等人。(2020b) 还研究了亚三叶草“叶子变红”的原因和植物影响。他们发现叶子变红是由低温引起的，重要的是，不会影响随后的植物生长。阮等人。(2020) 在“低”和“高”土壤肥力条件下检查了多年生高加索三叶草的根瘤菌。在几个不同年龄的田间地点对根瘤进行了研究，有趣的是，作者发现这种豆科植物特有的根瘤菌可以保持长达 42 年的有效性，而不管土壤肥力状况如何。土壤铝 (Al) 浓度对土壤酸性的草原豆类有重大影响。一些豆类似乎具有对抗土壤铝毒性的特定根机制，但我们对这一重要研究领域知之甚少。马等人。(2020) 在这个问题上贡献了一项有趣的工作，重点关注对铝敏感的豆科植物琉森，以及特定根系分泌物的释放，以潜在地减少高土壤铝的影响。这些研究人员得出结论，即使是琉森也显示出发展机制的潜力，例如从根部释放有机酸。另一方面，Young 等人。