植物根系吸水过程中根系水流阻力的变化特征

Variational Characteristics of Resistance to Water Flow in the Plant Root in the Course of Water Uptake by Plant Roots

以植物根系吸水的人工模拟试验所测得的数据为依据，运用水流的电模拟原理，定理分析了不同土壤水分水平处理下植物根系吸水过程中根系水流阻力各主要分量的大小、变化规律及其相对重要性．结果表明，在同一水分水平处理中，植物根内木质部传导阻力（Ｒｃ）随生长时间的推移而减小，随土层深度的加深而增大，土根接触阻力（Ｒｓｒ）、植物根系吸收阻力（Ｒｒ）随生长时间表现出先下降后上升阶段的动态变化特征；在不同水分水平处理中，Ｒｃ、Ｒｓｒ、Ｒｒ均随土壤湿度减小而大幅度增大；在植物根系水流阻力各分量中，Ｒｒ占根系水流阻力的比例为５５％～９６％，Ｒｓｒ约占根系水流阻力的４％～４５％，而Ｒｃ仅占根系水流阻力的７×１０－６。

This paper is concerned with analyzing quantitatively the magnitude, the variation with time and depth, and the relative importance of eace resistance to water flow in the plant root in the course of water uptake by plant roots in the different treatments of water supply levels, based on th simulating experiment data of soil moisture uptake by plant roots and on the electrical analog principle of water flow. The results indicated that the resistance to water conduction in root xylem ( R c) was decreased with growth time, was increased with increase of soil layer depth, the soil root contact resistance to water flow ( R sr ), the root resistance to water absorption ( R r), displayed the dynamic variation characteristics of the decreasing stage at first and the increasing stage at latter in the same treatment of water supply levels. R c, R sr , R r were greatly increased with the decrease of soil miosture in the different treatments of water supply levels. In the each resistance to water flow in the plant root, R r could reach the range of 55%～96% of the total resistance to water flow in the plant root, R sr could reach the range of 4%～45% of the total resistance to watee flow in the plant root, but R c could reach 7×10 -6 of the total resistance to water folw in the plant root, was so small that its relative importance in the plant root system could be omitted. Therefore, R r was the important factor which determined the velocity of water uptake by plant roots.