NaCl对小麦光合功能的伤害主要是由离子效应造成的

采用荧光动力学的方法来区分盐胁迫中的渗透因素和离子因素。用五种等渗Hogland培养液(分别含(NaCl,KCl,NaNO3,KNO3和PEG)对冬小麦处理两星期。结果，与对照相比，NaCl处理引起PSII受体侧电子库(CA/Fo)变小，PSII活性(Fv/Fo)、原初光能转化效率(Fv/Fm)、量子产量(Yield)与荧光化学猝灭系数(qP)下降，但使QB-非还原性PSII反应中心含量增加。然而，等渗的PEG处理并不产生类似的伤害。这表明渗透因素不是盐胁迫对光合作用造成伤害的主要原因。同时，KNO3处理对光合作用不产生伤害。由于NaCl和NaNO3处理均造成受体侧电子库变小，PSII活性和原初光能转化效率下降，并使QB-非还原性PSII反应中心增加，而等渗的PEG和KCl处理并不产生类似的伤害，这暗示Na+可能是盐胁迫影响光合作用的主要毒害离子。

Damage to Photosynthetic Functions of Wheat by NaCl Results Mainly from Its Ionic Effect

Means of the fluorescence induction kinetics were used to distinguish the osmotic factor and the ionic factor during NaCl stress. NaCl, KCl, NaNO3, KNO3, PEG solution of the same osmotic potential were used to treat the winter wheat cultured in Hogland solution for two weeks. The results showed that compared with control, the leaves from the NaCl treatment showed apparent decline in the size of acceptor side electron pool of PSII, PSII activity, the efficiency of primary conversion of light energy, quantum yield and qP; at the same time, NaCl treatment could give rise to great increase in the content of the QB_nonreducing reaction center, while the PEG treatment did not cause such changes. This experiment suggested that the osmotic factor might not be a major cause of NaCl stress to harm photosynthesis. In our experiment it was also shown that KNO3 treatment did not cause obvious damage on photosynthetic properties while NaCl and NaNO3 reatments cause great decline in Fv/Fm, Fv/Fo, the size of acceptor side electron pool and obvious increase in the content of Q-nonreducing reaction center. However, PEG and KCl treatment did not caused such changes. These results suggested that Na+ might be the major toxic ion to harm photosynthesis under salinity stress.