Scharwies Johannes Daniel, Dinneny José R
Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA, 94305, USA.
Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305, USA.
J Plant Res. 2019 May;132(3):311-324. doi: 10.1007/s10265-019-01089-8. Epub 2019 Feb 11.
Sufficient water availability in the environment is critical for plant survival. Perception of water by plants is necessary to balance water uptake and water loss and to control plant growth. Plant physiology and soil science research have contributed greatly to our understanding of how water moves through soil, is taken up by roots, and moves to leaves where it is lost to the atmosphere by transpiration. Water uptake from the soil is affected by soil texture itself and soil water content. Hydraulic resistances for water flow through soil can be a major limitation for plant water uptake. Changes in water supply and water loss affect water potential gradients inside plants. Likewise, growth creates water potential gradients. It is known that plants respond to changes in these gradients. Water flow and loss are controlled through stomata and regulation of hydraulic conductance via aquaporins. When water availability declines, water loss is limited through stomatal closure and by adjusting hydraulic conductance to maintain cell turgor. Plants also adapt to changes in water supply by growing their roots towards water and through refinements to their root system architecture. Mechanosensitive ion channels, aquaporins, proteins that sense the cell wall and cell membrane environment, and proteins that change conformation in response to osmotic or turgor changes could serve as putative sensors. Future research is required to better understand processes in the rhizosphere during soil drying and how plants respond to spatial differences in water availability. It remains to be investigated how changes in water availability and water loss affect different tissues and cells in plants and how these biophysical signals are translated into chemical signals that feed into signaling pathways like abscisic acid response or organ development.
环境中充足的水分供应对植物的生存至关重要。植物感知水分对于平衡水分吸收和水分流失以及控制植物生长是必要的。植物生理学和土壤科学研究为我们理解水分如何在土壤中移动、被根系吸收以及移动到叶片并通过蒸腾作用散失到大气中做出了巨大贡献。从土壤中吸收水分受土壤质地本身和土壤含水量的影响。水分在土壤中流动的水力阻力可能是植物水分吸收的主要限制因素。水分供应和水分流失的变化会影响植物体内的水势梯度。同样，生长也会产生水势梯度。已知植物会对这些梯度的变化做出反应。水分流动和流失是通过气孔以及通过水通道蛋白调节水力传导来控制的。当水分供应减少时，通过气孔关闭和调节水力传导来限制水分流失，以维持细胞膨压。植物还通过使根系向水生长以及优化根系结构来适应水分供应的变化。机械敏感离子通道、水通道蛋白、感知细胞壁和细胞膜环境的蛋白质以及响应渗透或膨压变化而改变构象的蛋白质可能作为假定的传感器。需要未来的研究来更好地理解土壤干燥过程中根际的过程以及植物如何对水分可利用性的空间差异做出反应。水分可利用性和水分流失的变化如何影响植物中的不同组织和细胞，以及这些生物物理信号如何转化为化学信号并输入到脱落酸反应或器官发育等信号通路中，仍有待研究。
