Effect of different drought stress levels on chlorophyll fluorescence indices of two bean cultivars

Chlorophyll fluorescence parameters and chlorophyll content are the most important factors for determining photosynthetic capacity in plant. For this purpose, an experiment was conducted to compare the resistance to different levels of drought stress, to evaluate the most important physiological indices and assess the function of photocysteine II using chlorophyll fluorescence parameters, chlorophyll content (chlorophyll a, b and a + b) and carotenoids of two bean cultivars in three levels of water deficiency including 30, 60 and 100% crop capacity (FC) in factorial arrangement in a randomized complete design with three replications in the greenhouse of the University of Guilan. Comparison of mean values showed that severe drought stress reduced the amount of chlorophyll content, Fv / Fm, Fv and, in contrast, increased the amount of fluorescence and Y (NPQ). The highest Fv/Fm ratio was observed in the control plants, while the highest reduction in Fv/Fm ratio in severe stress was obtained for the 18-G cultivar. In general, the interaction of drought cultivar was significant for all traits except Y (II), PAR and Fv/Fm. Also, Pearson correlation between total chlorophyll and Fv/Fm showed a positive and significant correlation (R = 0.86 **) in Ghaffar cultivar, but was not significant in G-18. Therefore, it can be concluded that Ghaffar cultivar can tolerate relatively high levels of drought by making changes in some physiological characteristics with better performance.