Photosystem II activity in the leaves and assimilative branches of alhagi sparsifolia Shap. under brief elevated temperature

Leaves and assimilative branches are crucial to the life cycle of Alhagi sparsifolia Shap. that is one of the main shrubs in the southern fringe of the Taklamakan desert. They reduce photosynthesis at midday during summer and exhibit different degrees of adaptability to severe environments. We investigated the changes in the PSII activity of leaves and assimilative branches of under elevated temperature and whether they have the same response and level of tolerance to different temperatures, thus to understand the roles of leaves and assimilative branches of A. sparsifolia in global warming. In this study, the kinetics of induced chlorophyll a fluorescence under heat-stress-induced inhibition of photosystem II in leaves and assimilative branches of A. sparsifolia after 15 min of treatment was investigated. The results show that both the activity and density of reaction centers of leaves are higher than assimilative branch at 35–48°C, and both in the leaves and assimilative branches were decreased above 45°C, the assimilative branches adapted better to the severe environment in terms of light energy transfer, light usage efficiency, and electron transport at 52°C. Assimilative branches had better adaptability to elevated temperature than leaves of A. sparsifolia suggesting that assimilative branches might be more adaptive to severe environment.