Abstract:

The effects of high temperatures on leaf traits，chloroplast ultra-structures，gas exchange，chlorophyll fluorescence parameters，antioxidant enzyme activity，pigment contents，and electrolyte leakage of three north highbush blueberry cultivars（‘Bluecrop’，‘Duke’and‘Brigitta’）were examined with four growth chambers by controlling growth temperatures at 25，30，35 and 40 ℃. The results showed that temperature barely changed the activity of superoxide dismutase（SOD）of the three cultivars，but significantly affected the activity of peroxidase（POD）and catalase（CAT）. Meanwhile，the chloroplast ultrastructure was seriously damaged at the growing temperature of 40 ℃ except for‘Brigitta’. Moreover，both the chlorophyll and carotenoid pigments of the three north highbush blueberry cultivars were decreased with the increase of temperature. The net photosynthetic rates（P_n），transpiration rates（T_r），and water use efficiency（WUE）also featured a similar trend. Moreover，the measurements on the electrolyte leakage and F_v/F_m indirectly supported the above conclusions and suggested that 30 ℃ and 35 ℃ had little effects on the leaf structure and function of the three blueberry cultivars，but 40 ℃ resulted in severe damages on the cellular membrane structure. These results suggested that three north highbush blueberry cultivars had different ability in resisting heat stress with‘Brigitta’>‘Bluecrop’>‘Duke’.

Key words: Vaccinium corymbosum, heat stress, gas exchange, pigments content, chlorophyll fluorescence, antioxidant enzyme activity