Study of photosynthetic gas exchange parameters and relative water content of flag leaf in soft wheat genotypes under different water supply conditions

The results of the study of the relative water content (RWC) and photosynthetic gas exchange parameters of the flag leaves in 21 soft wheat genotypes under rainfed conditions of Mountain Shirvan have been presented in the paper. The research was performed with drought-exposed and irrigated variants during the grain filling phase. RWC of the flag leaves of Vostorg, Murov 2, Tale 38, and Gyrmyzy gul 1 genotypes was higher both under drought and irrigated conditions. There was a positive correlation between RWC and earing time, and a negative correlation between RWC and plant height. The average difference in RWC between irrigated and drought-exposed variants for all genotypes was 10.1%. In 12thIWWYT no. 9 and 12thIWWYT no. 20 lines, this difference was high (26.5 and 19.6%), while in Gyzyl bughda, Murov 2, and Ferrigineum 2/19 genotypes, it was low (3.5, 3.6, and 2.9%). The highest values of the rate of photosynthesis were observed in the drought-exposed genotypes Sheki 1, Aran, Tale 38, and Zirva 85 (14.2, 14.8, 14.1, and 14.3 µmol CO2 m-2 s-1), and in the irrigated genotypes Aran, Vostorg, and 12thIWWYT no. 9 (24.9, 23.4, and 24.0 µmol CO2 m-2 s-1). Stomatal conductance (0.115, 0.120, 0.130, 0.164 mol H2O m-2 s-1), the concentration of CO2 in intercellular spaces (146.3, 156, 5, 181.7, and 213.7 µmol CO2mol-1) and the transpiration rate (3.32, 3.58, 4.13 and 4.44 mmol H2O m-2 s-1) were higher in the Sheki 1, Aran, Tale 38, and Zirva 85 varieties, which manifest higher photosynthetic rate under drought conditions than other genotypes. A significant positive correlation of RWC with the rate of photosynthesis, the stomatal conductance, the concentration of CO2 in intercellular spaces, and the rate of transpiration was found under drought stress conditions.