Effect of Branch-Bagged Shading on the Photosynthetic Physiology of Sweet Cherry Leaves in a Greenhouse Environment

The aim of this study was to improve understanding of the impacts of low-light stress induced by branch-bagged shading on photosynthetic physiology and biochemical composition. Eight-year-old ‘Tieton’ sweet cherry leaves and white parchment bags with a 23% shading rate were selected to cover ten 50 cm long branches for 10 d, 20 d, and 30 d followed by 10 d light restoring. The results indicated that when shading for 30 d, the net photosynthetic rate (PN) of the leaves, including stomatal conductance (gs), transpiration rate (E), intercellular CO2 concentration (Ci), superoxide dismutase (SOD), peroxide (POD), catalase (CAT), starch, and sugar contents were lower, whereas chlorophyll (Chl) and malondialdehyde (MDA) concentrations were higher than those in CK leaves. After 10-10 treatments, leaf parameters including SOD, POD, CAT, starch, and sugar levels were almost the same as those in control (CK; no shading) leaves; the opposite was true for Chl and MDA. However, after 10 d of no bag following 20 and 30 d of shading, the PN, Ci, E, and SOD, CAT, glucose, sorbitol, sucrose and starch levels were lower than those in CK leaves, whereas MDA levels were higher. At 20-10, there was no difference in leaf fructose levels compared to those in CK leaves; the Chl levels were higher. At 30-10, leaf fructose levels were reduced compared with those in CK leaves; Chl levels showed no difference. Therefore, sweet cherry leaves have robust recovery abilities; however, prolonged low-light stress can impede physiological restoration.