Effect of brackish water irrigation on the resistibility of winter wheat leaf to dry-hot wind

Brackish water irrigation was carried out in the North China Plain to alleviate the shortage of irrigation water resources. Dry-hot wind is one of the main meteorological disasters for winter wheat in the region; the effect of brackish water irrigation on the ability of winter wheat to resist dry-hot wind is yet inconclusive. Therefore, we conducted field experiments on winter wheat at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences. Brackish water irrigation with three salinity levels of 1 g·L^-1, 3 g·L^-1, and 5 g·L^-1 was set up, and the dry-hot wind simulation was conducted in the filling period. In this study, physiological parameters of winter wheat, such as photosynthetic rate, transpiration rate, and stomatal conductance of winter wheat were observed. The analysis of the experimental data during four consecutive years (2016-2019), showed the following results: 1) the brackish water with the salinities of 3 g·L^-1 and 5 g·L^-1 could reduce the photosynthetic rate of winter wheat leaves by 32.2% and 59.3%, the transpiration rate by 29.2% and 51.9%, and the stomatal conductance by 30.7% and 54.8% (P < 0.05), respectively. 2) Dry-hot wind could reduce the photosynthetic rate by 35.4%-86.6%, the transpiration rate by 35.6%-67.5%, and the stomatal conductance by 36.4%-69.4%, respectively. The irrigation with the salinity levels of 1 g·L^-1, 3 g·L^-1, and 5 g·L^-1 decreased the four-year average dry-hot wind stress index of the photosynthetic rate of winter wheat leaves from 0.55 to 0.45 and then increased to 0.74, while the leaf transpiration rate (the difference in the saturation of water vapor pressure) decreased from 0.54 to 0.26, then increased to 0.41; the four-year average dry-hot wind stress index of the stomatal conductance decreased from 0.56 to 0.28, then increased to 0.43. The above results showed that the physiological stress of brackish water irrigation on photosynthesis, transpiration, and stomatal behavior was similar to that of dry-hot wind, and the brackish salinity water (3 g·L^-1) irrigation could improve the physiological adaptability of winter wheat leaves to dry-hot wind, reducing the damage caused by dry-hot wind.