Abstract: 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 (R_s) and the resistance to water conduction in root xylem(R_c) are decreed with plant growth and inerasedwith increasing soil depth. The soil-root contact resistance to water flow (R_sr), the root resistance to water absorption (R_r ), and the total resistance to water flow in soil-plant spetem(R_A )display a dynamic variatbo characteristics: decreased at first, and then, inereased with time.R_s, R_c, R_sr, R_r and R_Aare greatly increased with decreasing soil moisture. Among all individual resistance to water flow in soil-plant system, R_r can reach to 55～96% of R_A. R_sr 4 -45%, R_s and R_c be omitted. Therefore, R_r is an important factor which determines the velocity of water flow.

Key words: Soil-plant system, Hydraulic resistance, Soil resistance, SRAP, Fusarium oxysporum of cucurbitaceae, Fusarium oxysporum f. sp. momordicae, genetic diversity