玉米单根木质部水势与径向水力导度的轴向变化

AXIAL CHANGES IN ROOT XYLEM WATER POTENTIAL AND RADIAL HYDRAULIC CONDUCTIVITY OF CORN

在前人用多个吸水小室测定单根径向水力导度和用不同渗透势溶液同时测定根木质部水势和径向水力导度的基础上 ,将这两种方法结合 ,用之研究了不同土壤水分条件下玉米单根木质部水势和径向水力导度的轴向变化。结果表明 :根木质部水势在距根尖 9cm以前是不断下降的 ,土壤干旱导致根木质部水势下降且前 7cm根木质部水势的下降幅度增大。根尖是对水分胁迫最敏感的部位。正常水分处理根径向导度在 3cm以前逐渐增加 ,3～ 1 0cm间达到最高值且维持稳定 ,1 0cm以后 ,根系径向导度下降。土壤干旱导致根径向导度下降 ,轴向上的下降部位提前 ,轴向变化的梯度减小。

Summary Radial hydraulic conductivity of root is usually measured using potometer method and both root xylem water potential and the conductivity can be measured by solutions with different osmotic potentials. In this paper an improved method was presented to measure axial changes in root xylem water potential and radial hydraulic conductivity of corn at different distances from root apex. The results indicated that root xylem water potential decreased continuously along 9 cm from root apex. Soil drought not only decreased root xylem water potential but also increased the decreasing degree of root water potential along 7 cm from the root apex. The apical zone was the most sensitive zone to water stress. Root radial hydraulic conductivity gradually increased within the first 3 cm from root apex, reached maximum and maintained constant between 3 cm and 10 cm and decreased thereafter. Water stress decreased radial hydraulic conductivity earlier and made the gradient of its axial changes smaller.