番茄叶片光合作用对快速水分胁迫的响应

采用聚乙二醇(PEG 6000)溶液控制番茄根际水势和叶片离体的方式设置了水分胁迫处理，测算了光合诱导过程中净光合速率、暗呼吸速率和CO₂补偿点等光合参数的变化.结果表明： 在1000 μmol·m^-2·s^-1光诱导下，水分胁迫处理的番茄叶片净光合速率(P_n)达到最大值所需时间缩短为对照的1/3，气孔导度(g_s)快速增大为对照的1.5倍.水分胁迫处理的番茄叶片光饱和点(LSP)比对照降低了65%～85%，而光补偿点(LCP)比对照增加了75%～100%，缩小了番茄叶片利用光能的有效范围.水分胁迫处理的番茄叶片最大光合能力(A_max)低于对照40%以上，暗呼吸速率(R_d)增大了约45%.可见，快速水分胁迫处理使番茄叶片气孔迅速开放，光合诱导初始阶段消失.水分胁迫导致植物利用光能的效率和潜力降低是植物生产力下降的重要原因，而气孔调节是番茄适应快速水分胁迫的重要生理机制.

Effects of land use change on ecosystem services in earth-rock mountainous area of Loess Plateau, Northwest China : A case study of Ningwu County

By using polyethylene glycol (PEG-6000) solution to regulate the water potential of tomato (Lycopersicon esculentum) rhizosphere to simulate water stress, this paper studied the dynamic changes of  net photosynthetic rate, dark respiratory rate and CO2 compensatory concentration of detached tomato leaves in the process of photosynthetic induction. Under 1000 μmol·m-2·s-1 of light induction, the time required to reach the maximum net photosynthetic rate of water stressed tomato leaves was shortened by 1/3, while the stomatal conductance was increased by 1.5 times, as compared to the non-stress control. Also, the light saturation point (LSP) of water-stressed tomato leaves was lowered by 65% to 85%, and the light compensation point (LCP) was increased by 75% to 100%, suggesting that the effective range of light utilized by tomato leaves was reduced. Furthermore, water stress decreased the maximum photosynthetic capacity of tomato leaves by 40%, but increased the dark respiration rate by about 45%. It was suggested that rapid water stress made the stomata of tomato leaves quickly opened, without initial photosynthetic induction stage. In conclusion, water stress could induce the decrease of plant light-energy use efficiency and potential, being the main reason for the decrease of plant productivity, and stomatal regulation could be the main physiological mechanism of tomato plants to adapt to rapid water stress.