Limited water availability is a major environmental factor constraining plant development and crop yields. One of the prominent adaptations of plants to water deficits is the maintenance of root growth that enables sustained access to soil water. Despite early recognition of the adaptive significance of root growth maintenance under water deficits, progress in understanding has been hampered by the inherent complexity of root systems and their interactions with the soil environment. We highlight selected milestones in understanding of root growth responses to water deficits, with emphasis on founding studies that have shaped current knowledge and set the stage for further investigation. We revisit the concept of integrated biophysical and metabolic regulation of plant growth, and utilize this framework to review central growth-regulatory processes occurring within root growth zones under water stress at sub-cellular to organ scales. Key topics include the primary processes of modifications of cell wall yielding properties and osmotic adjustment, as well as regulatory roles of abscisic acid and its interactions with other hormones. We include consideration of long-recognized responses for which detailed mechanistic understanding has been elusive until recently, for example hydrotropism, and identify gaps in knowledge, ongoing challenges and opportunities for future research.

中文翻译：

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不再那么隐藏：了解缺水条件下根系生长的进展和挑战

有限的水资源供应是限制植物发育和作物产量的主要环境因素。植物对缺水的显着适应之一是维持根系生长，从而能够持续获取土壤水分。尽管人们很早就认识到水分亏缺下根系生长维持的适应性重要性，但根系固有的复杂性及其与土壤环境的相互作用阻碍了理解的进展。我们重点介绍了理解根系生长对缺水反应的选定里程碑，重点是塑造当前知识并为进一步研究奠定基础的基础研究。我们重新审视植物生长的综合生物物理和代谢调节的概念，并利用该框架来回顾在亚细胞到器官尺度的水分胁迫下根生长区内发生的中央生长调节过程。关键主题包括细胞壁产量特性和渗透压调节的主要修饰过程，以及脱落酸的调节作用及其与其他激素的相互作用。我们考虑了长期以来一直被认可的反应，例如向水性，直到最近才对其详细的机理理解难以捉摸，并确定了知识差距、持续的挑战和未来研究的机遇。