Summer pruning of sweet cherry: a way to control sugar content in different organs

Sweet cherry trees (Prunus avium L.) of the cultivar Grace Star were pruned either in dormancy or in summer. The response was studied by analyzing the sugar content in different organs (flower bud, leaf, and fruit) at three sections of the canopy (inner, outer, and upper) using high-performance liquid chromatography. The effect of summer pruning was evaluated by measuring photosynthetic photon flux density (PPFD) and leaf chlorophyll content (SPAD).

In this study, the timing of pruning had a significant effect on sugar content in flower buds, leaves, and fruit. Trees pruned in summer had higher glucose, fructose, sorbitol, and sucrose content in flower buds, higher glucose and fructose contents in leaves, and lower fructose, sorbitol, and total sugar content in fruit than in trees pruned at dormancy. Higher average PPFD and lower SPAD values were measured in the inner canopy of trees pruned in summer. All measured parameters were influenced by position in the canopy. The lowest fructose and sorbitol contents in the flower bud, the lowest content of glucose, fructose, sorbitol, total sugars and the highest SPAD values in the leaf, while less dark and lighter fruit were measured in the inner part of the canopy.

Summer pruning affects sugar distribution in the tree by altering irradiation conditions within the canopy. Our results suggest that summer pruning is an effective technological measure to improve sugar content in the buds. A strong, well nourished flower bud is a good indication of high fruit production next season. © 2021 Society of Chemical Industry.