Physiological and proteomic analyses of Malus crabapples exposed to long-term warming and short-term heat shock treatments reveal the response characteristics of photosynthetic apparatus

Abstract

Malus crabapples are precious woody plants with unique ornamental and applied values. Their weak photosynthetic performance in subtropical summer disturbs the normal growth and development, but the underlying mechanism remains unclear. To facilitate their local cultivation, the differences in photosynthetic capacity between six Malus cultivars in subtropical regions from June to September as well as the response characteristics of photosynthetic apparatus in selected cultivar M. ‘Professor Sprenger’ to short-term, extreme heat shock were comprehensively investigated. The results showed that changes in environmental factors, especially the increase in air temperature, limited net photosynthetic rates (Pn) in different cultivars and caused changes in the shapes of the diurnal Pn curves. The utilization range and efficiency of these cultivars for CO2 and light energy also changed under high temperature environment, which resulted in decreased photosynthetic activity and differential photosynthetic adaptability. Interestingly, M. ‘Professor Sprenger’ possessed more activated reaction centers and efficient electron transport chains under heat shock, which ensured the absorption and utilization of light energy; while a series of differentially expressed photosynthesis-related/competitive proteins potentially promoted activity and stability of photosynthetic apparatus. These combined results provided a reasonable explanation for the strong photosynthetic performance of M. ‘Professor Sprenger’ under heat stress.