木质部汁液pH调控蒸腾速率的信号作用

Study on Signal Effect of the Xylem Sap pH in Regulating Transpiration Rate

采用压力室加压收集番茄木质部汁液，并测定和调节木质部汁液pH及叶片蒸腾速率变化的结果显示，对比原汁液，用KOH溶液调高pH（0.6～1.4）的蒸腾速率平均降幅大于14%；用盐酸调低pH（0.6～1.0）的蒸腾速率平均下降7%以上；用柠檬酸溶液调低pH（0.7～1.2）的蒸腾速率基本不变；用KOH溶液调高pH且加盐酸使pH复原后的蒸腾速率未见恢复。这表明汁液pH升高抑制蒸腾的效果可能被伴随的离子浓度变化对蒸腾的效果所抵消。

Root xylem saps were collected from tomato （Lycopersicon esculenturn L. ） with pressure chamber. The saps＇ pH were measured and half of them were buffered to specified pH＇s. Compares were made between the transpiration rates of detached tomato leaflets taking up xylem saps of different pH＇s. Ariseof0.6-1.4 unit in sap pH, after the adding of KOH to sap, resulted in a drop of more than 15 percent in transpiration. A drop of 0.6-1.0 unit in sap pH, after the adding of HCl, resulted in a drop of around 9 percent in transpiration. Generally speaking, the adding of Citric acid to sap did not affect transpirarion. After the successive adding of KOH and HCl, pH is restored but transpiration is not. It is proposed that change in the concentration of some ion, which coincided with change in pH, affected transpiration too.