压力室测定根系导水率方法探讨

用压力室连续测定了玉米根系长压和降压过程的导水率，结果表明，降压过程湍 得的根系导水率显著大于用升压过程的，并且前者的相关系数大于后者，这种差异是由于这两个过程中质外体途径细胞壁空间充水量不同造成的，开始升压时，由于细胞壁空间含水量低，质外体途径阻力大，导致非结构阻力；随着压力的升高，细胞壁空间含水量增大，质外体途径导度增大，减小甚至可以消除非结构阻力，降压法可以使根系快速复水，消除传统方法因长时间复水所致根结构的改变。建议用降压法测定根系导水率。

Probe the method of measuring root system hydraulic conductivity using pressure chamber

The hydraulic conductivity of maize root system was measured under ascending and descending pressure consecutively using a pressure chamber.The results showed that the hydraulic conductivity measured under descending pressure is remarkably greater than that under ascending pressure.The possible cause is that water content in intercellular spaces increased with increasing hydrostatic potential difference between soil solution and root xylem and,hence,increased apoplastic water flow.In the beginning of ascending pressure,the water content in intercellular spaces is low and apoplastic resistance is high,therefor results in non structural resistance.With pressure increasing,the water content in intercellular spaces increases,and consequently reduces non structural resistance in apoplastic pathway.It is concluded that the measurement of root system hydraulic conductivity under descending pressure can assure fast water recovery of root system,and therefore eliminates change of root structure that resulted from traditional long time water recovery prior to hydraulic conductivity measurement.We recommend the method of measuring root system hydraulic conductivity under descending pressure.