土壤-植物系统中水流阻力变化和分布规律的研究

Variation and distribution of hydraulic resistance in soil-plant system

以植物根系吸水的人工模拟试验测得资料为依据，运用水流的电模拟原理，定量分析了不同土壤水分水平处理下土壤-植物系统中水流阻力各分量的大小、变化规律及其相对重要性．结果表明，土壤阻力（Rs）、根内木质部传导阻力（Rc）随生任时间的推移而减小，随土层深度的加深而增大，土根接触组力（Rsr）、根系吸收阻力（Rr）、土壤-植物系统中水流总阻力（RA）随时间表现出先下降后上升阶段的动态变化特征，Rs、Rc、Rsr、Rr、RA均随土壤湿度减小而大幅度增大；在土壤-植物系统水流阻力各分量中，Rr占RA的比例为55～96％，Rsr约占RA的4－45％，而Rs、Pc相对可忽略不计，故Rr，是决定液态水流速率的重要因素．

Based on the simulation experiment of soil water uptake by plant roots and on the electrical analog principle of water flow, the magnitude, the variation with time and depth, and the relativesignificance of each resistance to water flow in soil-plant system at different water supply levelsare analysed. The results indicate that the resistance to water flow in soil (Rs) and the resistance to water conduction in root xylem(Rc) are decreed with plant growth and inerasedwith increasing soil depth. The soil-root contact resistance to water flow (Rsr), the root resistance to water absorption (Rr ), and the total resistance to water flow in soil-plant spetem(RA )display a dynamic variatbo characteristics: decreased at first, and then, inereased with time.Rs, Rc, Rsr, Rr and RA are greatly increased with decreasing soil moisture. Among all individual resistance to water flow in soil-plant system, Rr can reach to 55 ～ 96% of RA. Rsr 4 -45%, Rs and Rc be omitted. Therefore, Rr is an important factor which determines the velocity of water flow.