Hail Net Effect on Photosynthetic Rate and Fruit Color Developent of ‘Starkrimson’ Apple Trees

Abstract

Photosynthetically active radiation (PAR) distribution, net photosynthesis (Pn) and fruit color were measured on ‘Starkrimson Delicious’ apple ( Malus × domesticaBorkh.) trees and fruits protected against hail by white or black nets, as well as unprotected controls. PAR levels were reduced by 45 and 63% by white and black nets respectively. Net color and canopy position showed a highly significant interaction for PAR distribution. The inner canopy of trees under black hail nets received the least PAR. PAR measured in the upper canopy was significantly higher than in the lower canopy. No significant differences in Pn were found between trees under white nets and controls, but both were higher than trees under black nets. Highly significant differences were found for canopy position; the lower-internal canopy position yielded the lowest Pn values. Fruit color followed the same pattern of influence of canopy position and orientation. Fruit color measurements L-value and hue angle (°h) were directly affected by hail nets. Fruits in the upper tree stratum had better color, with lower L and °h values. Fruit color was mostly defined by fruit position within the canopy.