Effect of plastic roof and high tunnel on microclimate, physiology, vegetative growth and fruit characteristics of 'Santina' sweet cherry

The objective of the present study was to evaluate the effect of plastic covers (roof and high tunnel) on microclimate, physiological response, vegetative growth, and physicochemical fruit characteristics of 'Santina' sweet cherry trees during two seasons. The study was conducted in a commercial orchard established in a Mediterranean climate in Chile. The covers reduced the incident solar radiation, generating a darker environment under the roof than under the high tunnel. At the upper tree level, the microclimate under both covers tended to be warmer and drier than in the open air; conversely, at the lower level, conditions under the roof were cooler and fresher than in the open air and high tunnel. These variations generated similar trends in thermal accumulation and environmental stress indicators in the two heights analyzed. Sweet cherry trees under both covers showed lower water stress in the first season, expressed as increased stomatal conductance and water potential compared to those grown in the open air; however, after harvest, stress was higher under both covers. Vegetative growth under the covers was affected only in one season. Fruit under the covers had slightly less intense color, and reduced firmness and titratable acidity: the differences were maintained after 30 days of storage in a modified atmosphere. Similarly, anthocyanin concentration in the fruit skin, total phenolic content, and antioxidant capacity in the edible fraction tended to be reduced. Fruit harvest was up to 29 days earlier in the high tunnels than in the open air. Considering that covers alter the physiological performance of the trees and fruit quality, adequate ventilation should be considered to avoid deteriorating the quality of the fruit and thus improve the crop's competitiveness in Chile's central zone.