Influence of photosynthetic radiation on the morphological and physiological variability of northern highbush blueberry (Vaccinium corymbosum L.) cv. Duke and Brigitta.

Authors: V. Sotelo, T.E. Lobos, J.B. Retamales *

Several studies have described the changes of northern highbush blueberry (NHB) plants (Vaccinium corymbosum L.) in response to different variables but reports on intra-plant variability are scarce. Our objective was to study morphological and physiological changes in leaves during the season, as affected by three factors: cultivar (‘Duke’ or ‘Brigitta’); position within the canopy (top: 121-180, mid: 61-120 or basal: 0-60 cm) and orientation (north, south, east, west, or internal). Seven-year-old blueberries planted in east-west direction and growing in a commercial field in Linares, Chile (Lat. 35° 49' S) were used. Morphological (leaf area: LA, specific leaf area: SLA, leaf dry matter: LDM and stomatal density: SD), and physiological measurements (total chlorophyll: TC, leaf N, stomatal conductance: SC, and leaf temperature: LT) were done on mature leaves at postharvest of season 1 and at pre-harvest, harvest, and post-harvest of season 2. Radiation (percent full sun; %FS) was measured on sunny days. The single factors, cultivar and position, and their interaction were most influential on morphological and physiological traits of blueberry leaves. LT was the most sensitive leaf trait. Light availability varied with cultivar (‘Duke’ had a more open canopy), and with position (top one had higher light availability). Within the season, the factor cultivar had a consistent effect on SLA, SD, and leaf N, while the factor position consistently influenced leaf N and LT.