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通过气体交换和叶绿素荧光猝灭动力学研究了盐胁迫对甜高粱幼苗碳同化能力和光系统Ⅱ光化学效率的影响。结果表明,50和100mmolL-1的盐(NaCl)处理对叶绿素含量、相对含水量和膜质过氧化程度影响很小;200mmolL-1NaCl处理导致叶绿素含量和相对含水量明显下降、膜质过氧化程度增加。50mmolL-1NaCl处理未影响甜高粱幼苗的净光合速率;NaCl浓度大于50mmolL-1时,净光合速率开始迅速降低;同时,气孔限制值(Ls)也减小;而且,光合能力的下降未能通过增加CO2浓度得以恢复。甜高粱幼苗的初始荧光(Fo)、最大荧光产量(Fm)和最大光化学效率(Fv/Fm)只在200mmolL-1NaCl处理时有较大程度的下降。此外,50mmolL-1NaCl胁迫也没有影响甜高粱幼苗的荧光猝灭动力学参数;当NaCl浓度大于50mmolL-1时,光系统Ⅱ开放反应中心转化效率(F′v/F′m),光化学猝灭系数(qP)和光系统Ⅱ实际光化学效率(ΦPSⅡ)开始下降,而非光化学猝灭(NPQ)提高。因此认为,盐胁迫导致的碳同化能力的降低属于非气孔限制;碳同化能力的降低改变了甜高粱光系统Ⅱ的激发能利用和分配。100mmolL-1盐胁迫条件下,甜高粱幼苗主要通过增加热耗散来消耗过多的激发能,而200mmolL-1盐胁迫条件下通过减少光能吸收和增加热耗散来维持光能捕获和利用的平衡。
Effects of salt stress on carbon assimilation ability and photosystem Ⅱ photochemical efficiency of sweet sorghum seedlings were studied by gas exchange and chlorophyll fluorescence quenching kinetics. The results showed that the salt (NaCl) treatments of 50 and 100 mmol L-1 had little effect on the content of chlorophyll, relative water content and the degree of membrane peroxidation. The content of chlorophyll and relative water content of 200 mmol L-1 NaCl decreased significantly, increase. The net photosynthetic rate of sweet sorghum seedlings was not influenced by 50 mmolL-1 NaCl treatment. When the NaCl concentration was higher than 50 mmolL-1, the net photosynthetic rate began to decrease rapidly. At the same time, the stomatal limitation (Ls) also decreased. Moreover, the decrease of photosynthetic capacity failed Increase CO2 concentration to recover. The initial fluorescence (Fo), maximum fluorescence yield (Fm) and maximum photochemical efficiency (Fv / Fm) of sweet sorghum seedlings decreased only with 200mmolL-1NaCl treatment. In addition, the fluorescence quenching kinetic parameters of sweet sorghum seedlings were also not affected by 50 mmolL-1 NaCl stress. When the NaCl concentration was higher than 50 mmolL-1, the conversion efficiency (F’v / F’m) of photosystem Ⅱ open reaction center, photochemical quenching The coefficient (qP) and the actual photochemical efficiency of PSⅡ (ΦPSⅡ) began to decline, while the non-photochemical quenching (NPQ) increased. Therefore, it is considered that the reduction of carbon assimilation ability caused by salt stress belongs to non-stomatal limitation, and the decrease of carbon assimilation ability changes the utilization and allocation of excitation energy of photosystem Ⅱ of sweet sorghum. Under 100 mmol L-1 salt stress, sweet sorghum seedlings consumed excessive excitation energy mainly by increasing heat dissipation, whereas light harvesting and utilization were maintained by reducing light energy absorption and increasing heat dissipation under 200 mmol L-1 salt stress Balance.