Beneficial Effect of Exogenously Applied Calcium Chloride on the Anatomy and Fast Chlorophyll Fluorescence in Rhododendron × pulchrum Leaves Following Short-Term Heat Stress Treatment

The heat tolerance of plants can be improved by using exogenous calcium chloride (CaCl2) to cope with temperature fluctuations. Since global climates continue warm, it is important further explore the way in which respond stress use CaCl2. We aimed effect CaCl2 on leaf microstructure, epidermal ultrastructure, and chlorophyll a fluorescence Rhododendron × pulchrum (R. pulchrum) under stress. In leaves R. treated CaCl2, compared control, thickness epidermis, spongy tissues, stomatal aperture increased, whereas stomata density ratio closed/open decreased. conditions, values maximal photochemical efficiency photosystem II (Fv/Fm), performance index an absorption basis (PIABS), quantum yield for reduction terminal electron acceptors acceptor side PSI (φRo), energy absorbed per unit cross-section photosynthesizing object at moment achieving maximum (ABS/CSM) all decreased, dissipation (φDo) increased significantly. However, these differences disappeared when was This suggests that improve regulating anatomical structure behavior cells leaves, protecting stability photosystems I improving transfer from QA QB. Our study could provide theoretical breeding, research, utilization context warming.