Physiological effects of multi-functional nets applied to cherry trees grafted on rootstocks with different vigor

In cherry orchards, multi-functional nets represent very useful protection tools against biotic and abiotic stressors, such as Drosophila suzukii, rain, or hail. At the same time, the shading effect of the net can alter the microclimate within the canopy, thus affecting tree physiological processes. This work aims at testing the effect of "Keep in Touch (R)" multi-functional nets on water relations, leaf gas exchanges, and fruit growth of 'Black Star'/cherry trees grafted on the semi-vigorous ('CAB 6P') and the semi-dwarfing ('Gisela (TM) 6') rootstocks. Midday stem (Psi(stem)), leaf (Psi(leaf)), and fruit (Psi(fruit)) water potential, leaf photosynthesis, stomatal conductance, and transpiration, as well as seasonal fruit growth, were assessed in post-veraison, while productivity and fruit quality were determined at harvest. Results showed how nets did not diminish photosynthesis in the internal part of the canopy of trees grafted on 'GiselaT6', while stem water potential decreased, thus improving their water status. On the contrary, nets induced a reduction of photosynthesis in the internal part of 'CAB 6P' trees, whose canopies were denser because of higher vigor of the combination. Similarly, fruit growth and quality on 'CAB 6P' trees were reduced under nets due to decreased fruit water potential, which caused these cherries to be weaker sinks for water and carbohydrates. Based on these results, we can conclude that "Keep in touch (R)" nets, besides their protective function against biotic stressors, can bring benefits to the high density planting systems, while they can induce some negative effects on fruit quality in highly vigorous orchards.