麻疯树幼苗对干旱胁迫的响应

以不同浓度(5%～25%)的聚乙二醇(PEG-6000)模拟干旱胁迫处理麻疯树三叶期幼苗，研究了不同程度干旱胁迫下麻疯树叶片光合特性及其对干旱的耐受能力.结果表明:在较低浓度PEG(≤15%)处理下，随PEG浓度的增加，麻疯树叶片净光合速率(P_n)、气孔导度(G_s)、胞间CO₂浓度(C_i)、PSⅡ实际光化学量子产量(Φ_PSⅡ)、光化学猝灭(q_P)和表观光合电子传递速率(ETR)下降，PSⅡ原初光能转化效率(F_v/F_m)轻微下降，水分利用效率(WUE)则逐渐升高，非光化学猝灭(NPQ)明显上升，初始荧光(F_o)无显著变化(P＞0.05)；在高浓度PEG(＞15%)处理下，C_i随PEG浓度的增加而显著上升，P_n、G_s和WUE持续下降，F_v/F_m、Φ_PSⅡ、q_P和ETR下降幅度明显增大，F_o显著上升，而NPQ下降.低浓度PEG处理导致麻疯树叶片P_n下降主要是由气孔因素造成的；在高浓度PEG处理下，P_n的下降则是由非气孔和气孔因素的共同限制作用造成的.当PEG浓度<20%时，虽然出现P_n下降，但光合机构未受损伤.经15 d高浓度PEG处理的植株叶片，在胁迫解除后光合活性能够迅速恢复，且植株可以存活.说明麻疯树对干旱胁迫有较强的耐受能力.

Responses of Jatropha curcas L. seedlings to drought stress.

By adding different concentrations (5%-25%) of polyethylene glycol (PEG) into Hoagland solution to simulate a gradient of drought stress, the photosynthetic characteristics and drought resistance of Jatropha curcas L. seedlings were investigated. The results showed that when treated with lower concentrations (< or = 15%) of PEG, the photosynthetic rate (Pn), stomatal conductance (Gs), and intercellular carbon dioxide concentration (Ci) of the seedlings decreased with increasing PEG concentration, while the chlorophyll fluorescence parameters optimal/maximal quantum yield of PS II (Fv/Fm) decreased slightly and minimal fluorescence (Fo) was almost unaltered. The certain reduction of actual photochemical efficiency of PS II in the light (Phi(PS II)), coefficient of photochemical quenching (qP), and apparent electron transport rate (ETR) was associated with a significant increase in non-photochemical quenching (NPQ), whereas as the PEG concentration was increased to higher than 15%, Ci increased remarkably, Pn, Gs, and WUE had a sustained decrease, while Fv/Fm, Phi(PS II), qP and ETR decreased more significantly, Fo increased rapidly, and NPQ decreased. The reduction of Pn under low concentration PEG was mainly due to stomatal limitation, while that under high PEG concentration was referred to the combination of non-stomatal and stomatal limitation. When the PEG concentration was lower than 20%, Pn decreased but photosynthetic structure was not damaged. The recovery of PS II activity and the survival of plant were found after the severe drought stress was removed 15 days later. It was concluded that Jatropha curcas had stronger tolerance to drought stress.