根压的本质(英文)

The nature of root pressure

在植物弱蒸腾情况下 ,木质部的水分处于正压状态 ,这种压力叫根压 .关于根压有不少相互矛盾的假说 ,大致可分为两大类 :单相模型和双相模型 .单相模型不强调水流方向 ,基本上只将根中的共质体作为一层连续的半透膜看待 .单相模型包括分泌理论、电渗理论、渗透理论和渗透持续梯度理论 .而根压的双相模型认为根中有具有不同反弹系数的双膜系统 ,即高反弹系数的外膜和低反弹系数的内膜 .本文对这些根压理论进行了总结和分析 ,并结合一些新的研究成果 ,特别是对根中薄壁细胞有节律性地收缩和松弛及对水通道蛋白的研究 。

The positive xylem pressure, often occurs with low transpiration rate, is termed as root pressure. Various mechanisms have been suggested for the nature of root pressure. All the explanations can be classified into two major groups: monophasic and biphasic models. The monophasic models advocate a unidirectional water flow, taking the whole symplast of root as a semi permeable membrane. The monophasic models include secretion theory, electro osmotic theory, osmotic theory and osmotic standing gradient theories. The biphasic models propose an oscillation in time of water uptake and water release by the symplast. Both uptake and release would take place in two directions. This review summarizes those models with discussion of current knowledge of root parenchyma cells including contraction and relaxation, aquaporins, cytoskeleton, and actomyosin like proteins.