Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat under salt stress

Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied, The results showed that several parameters associated with PS II functions, e.g. Fv/Fo, Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PS II functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the Q(B)-non-reductive PS II reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PS II reaction center (RC) and repair the reversible inactivated PS II RC. Under higher concentration of salt stress, PS II reaction centers were seriously damaged during photoinhibition, the Q(B)-non-reductive PS II RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of Q(B)-non-reductive PS II RC in the course of restoration under dim light.