Study on the relation between the effects of water stress on the flag leaf chlorophyll a fluorescence induction kinetics and the yields of spring wheat genotypes in late growth season

The effects of water stress on chlorophyll content of the flag leaf and the flag leaf chlorophyll a fluorescence induction kinetics of spring wheat genotypes in late growth season were studied by using SPAD 501 portable chlorophyll meter and OS1 FL modulated chlorophyll fluorometer. Meanwhile, the yields of the tested varieties were studied. The result indicated that chlorophyll a fluorescence induction kinetics curves of spring wheat flag leaf were changed obviously during water stess. The decrease of variable fluorescence yield (Fv values), the ratio of the variable to maximal fluorescence (Fv/Fm), the ration of the variable to minimal fluorescence (Fv/Fo) and photochemical quantum Yield under water stress suggested that the primary light energy conversion of PSⅡ, the potential activities of PSⅡand photosynthetic electron transport and the carbon asimilation had been inhibited. Meanwhile, different genotypes have different responses to water stress. The results of the experiment also showed that the relation between the yields of the eight spring wheat genotypes and the photosynthetic indexes above were not significant.\;