The Effect of the Main Components of Climate Change onPphotosynthetic Efficiency and Grain Yield of Wheat Genotypes under Dryland Conditions

To evaluate the impact of the components of climate change on the photosynthetic efficiency and grain yield of four dryland wheat genotypes (Sardari, Ohadi, Varan, and Ivan), an experiment was carried out in two conditions of the controlled environment and the field conditions in the 2021-2022 growing season. In the controlled environment, a split-plot experiment based on a randomized complete block design including temperature (25±3°C and 34±3°C) in the main plots, carbon dioxide (380 to 480 and 800 to 900 ppm) in sub-plots and drought stress (normal and water stress) were placed in sub-sub-plots. In the field conditions, a split plot experiment based on RCBD was carried out with three planting dates of 7, 22 October, and 6 November in the main plots and cultivars in the sub-plots. The components of climate change in all cultivars reduced Fmʹ and led to an increase in NPQ, and the activation of the non-photochemical quenching pathway and thermal energy dissipation through the Xanthophyll cycle and reduced ETR. The interaction effect of temperature and high carbon dioxide in all cultivars and heat in Sardari, Ohadi, and Ivan cultivars had higher electron transfer rates than other factors. On the first planting date, due to the adaptation of the plants to the environmental conditions grain yield was more by 23% and 100% than that of the second and third dates of sowing. It was concluded that despite the stress conditions dryland wheat genotypes have a suitable adaptation for energy disposal in the photosynthetic system.