Abstract: Aims Loquat (Eriobotrya japonica) is evergreen tree that often suffers photoinhibition or photodamage at low temperature in winter, which affects its growth. Therefore, this study explored the photoinhibition of two photosystems of loquat leaves in winter. Methods In this study, the photoinhibition of two photosystems of loquat leaves in winter was compared using simultaneous measurements of chlorophyll fluorescence and 820 nm light reflection. Important findings From autumn to winter, the maximum quantum yield of photosystem II (PSII) (Fv/Fm) in loquat leaves decreased significantly, while the photosynthetic electron transfer capacity at both the donor and acceptor sides of PSII did not change. The activity of photosystem I (PSI) did not change either. However, the actual photochemical efficiencies of both PSII and PSI decreased significantly. Non-photochemical quenching decreased significantly under high light. From winter to spring, the value of Fv/Fm in loquat leaves increased significantly. The electron transfer capacity at the acceptor side of PSII and the activity of PSI also decreased. Moreover, the actual photochemical efficiency of PSII increased significantly, while that of PSI remained unchanged. Non-photochemical quenching increased significantly under high light. These results indicate that the photoinhibition of PSI occurred later than PSII in loquat leaves in winter. The activity of PSI also recovered slowly. Photoinhibition of PSII occurred earlier, and its activity recovered earlier.

Key words: Eriobotrya japonica, chlorophyll fluorescence, 820 nm light reflection, photoinhibition