Chair of Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, D-95444, Bayreuth, Germany.
Department of Land, Air and Water Resources, University of California Davis, Davis, CA 95616, USA.
J Exp Bot. 2022 Jun 2;73(11):3330-3338. doi: 10.1093/jxb/erac114.
Sufficient water is essential for plant growth and production. Root hairs connect roots to the soil, extend the effective root radius, and greatly enlarge the absorbing surface area. Although the efficacy of root hairs in nutrient uptake, especially phosphorus, has been well recognized, their role in water uptake remains contentious. Here we review recent advances in this field, discuss the factors affecting the role of root hairs in water uptake, and propose future directions. We argue that root hair length and shrinkage, in response to soil drying, explain the apparently contradictory evidence currently available. Our analysis revealed that shorter and vulnerable root hairs (i.e. rice and maize) made little, if any, contribution to root water uptake. In contrast, relatively longer root hairs (i.e. barley) had a clear influence on root water uptake, transpiration, and hence plant response to soil drying. We conclude that the role of root hairs in water uptake is species (and probably soil) specific. We propose that a holistic understanding of the efficacy of root hairs in water uptake will require detailed studies of root hair length, turnover, and shrinkage in different species and contrasting soil textures.
充足的水分是植物生长和生产的必要条件。根毛将根与土壤连接起来，扩展了有效根半径，并大大增加了吸收表面积。尽管根毛在养分吸收方面的功效，特别是在磷的吸收方面，已经得到了很好的认识，但它们在水分吸收中的作用仍然存在争议。在这里，我们回顾了这一领域的最新进展，讨论了影响根毛在水分吸收中作用的因素，并提出了未来的方向。我们认为，根毛长度和收缩对土壤干燥的反应，解释了目前可用的明显矛盾的证据。我们的分析表明，较短且脆弱的根毛（例如水稻和玉米）几乎没有对根的水分吸收做出贡献。相比之下，相对较长的根毛（例如大麦）对根的水分吸收、蒸腾作用以及植物对土壤干燥的响应有明显的影响。我们得出结论，根毛在水分吸收中的作用是特定于物种（可能还有土壤）的。我们建议，要全面了解根毛在水分吸收中的功效，需要对不同物种和不同土壤质地的根毛长度、周转率和收缩进行详细研究。
