柠檬酸盐对水稻根系吸收磷酸盐的影响

Effect of Citrate Excretion on Phosphate Uptake by Rice( Oryza sativa L. ) Roots

将水稻(Oryza sativa L.)根系区域分为根毛区域和根毛外区域,用米氏动力学方程描述主根和根毛表面对磷酸盐的吸收,把根毛磷酸盐的吸收作为扩散方程的源汇项,在Kirk模型的柠檬酸盐和磷酸盐的相互作用机制基础上,建立水稻根系吸收磷酸盐模型.利用该模型探讨水稻主根分泌柠檬酸盐对根系吸收磷酸盐的影响.数值模拟的结果表明,在根毛区域,液态磷酸盐浓度存在梯度变化;在根毛外区域,液态磷酸盐浓度低于Kirk模型,最大低于1.839μmol·L-1;水稻主根分泌柠檬酸盐的含量随着生长时间的增大而增加,然后保持不变;柠檬酸盐促进固态磷酸盐从土壤颗粒表面中解吸出来;在根毛生长的初期,主根吸收液态磷酸盐强于根毛,在16 h后,根毛吸收液态磷酸盐在水稻根系吸收中占主导作用.主根分泌柠檬酸盐和根系形态共同决定水稻根系对磷酸盐的吸收量.

Based on the Kirk model, we divide the rice zone into the root hair zone and out- side the root hair zone, describe the root and root hair phosphate uptake with the Michaelis-Menten kinetic, and take root hair uptake as a sink term in the diffusion equation. The improved model is used to investigate the effect of citrate exudation of the main root on phosphate uptake by the rice root system. The numerical results show that the phosphate concentration gradient dynamically de- velops within the root hair zone. The phosphate concentration in the soil solution is below the Kirk model, the maximum below 1. 839 -mol - L-1. The citrate exudation by root increase as time, af- terwards remain the same level. The citrate promote solubility of phosphate on the surface of the soil particles. At the beginning of the root hair growth, the phosphate uptake of root is larger than the root hair, the phosphate uptake of the hair root dominate the phosphate uptake after 16 hours. We proposed that citrate exudation of the main root and root morphology of the rice codetermine the in- flux of phosphate uptake by root system.