2010 Volume 9 Issue 4 Pages 455-460
Photosynthetic characteristics measured with the leaves of ‘Weymouth’ highbush blueberry (Vaccinium corymbosum L.) and ‘Tifblue’ rabbiteye blueberry (V. ashei Reade) in phytotron were compared with regard to their responses to light intensity (0-2,000 μmol·m−2·s−1) and temperature (15-35°C). As temperature increased, photosynthetic rates of both cultivars increased. Photosynthetic rates of ‘Weymouth’ were higher than those of ‘Tifblue’ under low temperature conditions (15-20°C). However, there was no difference in photosynthetic rates measured under high temperature conditions (25-35°C), but ‘Weymouth’ showed higher transpiration rates and lower water use efficiencies (WUE) than ‘Tifblue’. Furthermore, photosynthetic characteristics of ‘Blueray’ highbush blueberry under high temperature conditions (28 and 35°C) were similar to those of ‘Weymouth’ under high temperature conditions. These findings show that photosynthetic characteristics of leaves could be related to the suitability of highbush blueberries to cool conditions, and to the heat tolerance and drought resistance of rabbiteye blueberries. WUE values measured at high temperature >35°C and high light intensity >1,000 mmol·m−2·s−1 could be helpful as indices for evaluating and selecting blueberry plants with heat tolerance. Transpiration rates increased at high temperature and high light intensity, which suggested that shading in summer to control light intensity under 1,000 μmol·μ−2·s−1, a light saturation point, could be useful for preventing water loss of the plants.
