Effects of moisture stress on dry matter yield, water relations, chlorophyll fluorescence and gas exchanges in Salvia sahendica L.

The reduction of photosynthesis is the most important reason for the decrease in productivity under drought stress conditions. For this purpose, this research was carried out to investigate the effect of moisture stress on shoot dry matter yield, water relations, chlorophyll fluorescence, photosynthesis, and gas exchanges in Salvia sahendica L. at Mobarakeh city, Isfahan, in 2016. The treatments included irrigation intervals of 4 (control), 8, 12 and 16 days conducted in a randomized complete block design under field conditions. The results of the analysis of variance showed that the effect of irrigation intervals treatments was significant on shoot dry matter yield, water relations, chlorophyll fluorescence, photosynthesis rate, and leaf gas exchanges. Based on the results of mean comparison, with increasing irrigation interval from 4 to 16 days, photosynthesis rate, transpiration rate, stomatal conductance, photosystem II efficiency, shoot dry matter yield, and harvest index decreased significantly by 55, 62, 73, 57, 58 and 45 percentage, and water use efficiency and gas exchanges increased significantly by 35 and 92 percentage, respectively. For the attributes mentioned above, the irrigation intervals of 8 and 12 days had no significant difference with control treatment. By increasing stress, the amount of intercellular carbon dioxide below the stomatal cells did not change significantly, but the leaf temperature increased significantly. Correlation coefficients showed that the shoot dry matter yield had a positive and significant correlation with photosynthesis and transpiration rate, stomatal conductance, and photosystem II efficiency, and a negative and significant correlation with leaf temperature, gas exchanges, and water use efficiency. Regarding the absence of significant difference between the indices studied at 8 and 12-day irrigation intervals in comparison with normal irrigation regime (control treatment), it can be concluded that the irrigation interval of 12 days is an optimum irrigation regime for using this plant in arid and semi-arid regions.