轻度盐胁迫对甜高粱光合作用激发能分配的影响

Effect of Slight Salt-stress on Excitation Energy Distribution of Photosynthesis in Sweet Sorghum

以甜高粱(Sorghum bicolor Moench)叶片为试材,采用不同盐(NaCl)浓度处理,测定光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、气孔限制(Ls)、初始荧光(Fo)、最大荧光(Fm)、光合系统II的光化学效率(Fv/Fm)、天线转化效率(Fv’/Fm’)、光化学淬灭(qp)、实际光化学效率(ΦPSII)和非光化学淬灭(NPQ),研究盐胁迫对光合机构、光合作用和光系统II光化学活性的影响。结果表明:相对于对照,100mmol.L-1NaCl处理对甜高粱的光合作用影响较大,而50mmol.L-1NaCl处理影响不大。盐胁迫导致的光合作用能力下降未能通过增加CO2浓度得以恢复,此外100mmol.L-1NaCl处理的Fv’/Fm’,qp和ΦPSII低于50mmol.L-1NaCl处理和对照,而NPQ却比50mmol.L-1NaCl处理和对照大,表明盐胁迫使光合作用降低的原因是非气孔限制。盐胁迫还改变了甜高粱的激发能分配方式,100mmol.L-1NaCl处理主要通过热耗散来消耗过多的激发能。

Pn, Gs, Ci, Ls, Fo, Fm, Fv/Fm, Fv^＋/Fm^＋, qp, φPSII and NPQ were used to study the effect of salt-stress on photosynthetic rate and excitation energy distribution in sweet sorghum leaves. The results showed that Photosynthetic rate of 100mmol·L^-1 NaCI treatment were affected more strongly than that of the 50 mmol·L^-1 NaCl treatment compared with control. Reducing of carbon assimilation at high salinities did not resume when CO2 concentrition increased. Moreover, Fv^＋/Fm^＋, qp and φPSII of lOOmmol·L^-1 NaCI treatments were significantly depressed, and NPQ significantly increased with respect to 50 mmol· L^-1 NaCI treatment and control. These indicated that excessive excitation energy was dissipated by the form of heat. The decline of photosynthetic rate was mainly caused by nonstomatal limitations. Salt-stress also changed the way of excitation energy distribu- tion, and plant under lOOmmol· L^-1 salt-stress dissipated excessive excitation energy by the form of heat.