Seasonal Changes In the Photochemistry, Quantum Efficiency and Net Photosynthesis of the Wild Blueberry

The seasonal variation carotenoid concentration, chlorophyll a and b levels, dark (Fv/Fm) and light adapted (Fv’/Fm’) dark and light adapted variable to maximal chlorophyll fluorescence (an indication of the quantum efficiency of PSII photochemistry) and net photosynthesis of the wild blueberry (Vaccinium angustifolium Ait.) was examined in the vegetative (i.e., sprout) and cropping phases of production. Chlorophyll levels ranged from 2.0 to 12 µg·cm^-2 and 0.042 to 1.4 µg·cm^-2 for chlorophyll a and b respectively, were significantly lower in the cropping phase of production, and were also lower in the latter stages of the growing season. Similarly, carotenoid concentrations ranged from 0.67 to 4.1 µg·cm^-2 and were lower in the cropping phase of production. However, caretonoid concentration and dark and light adapted variable to maximal chlorophyll fluorescence (Fv/Fm and Fv’/Fm’) decreased marketably at the mid point of the growing season presumably as a result of photoinhibition. Net photosynthetic values of upright stems ranged from 2.1 to 7.6 µmol·m^-2·s^-1, were substantially higher in the vegetative phase of production and also decreased significantly in the latter part of the growing season. Results from this investigation indicate that the wild blueberry has a relatively low photosynthetic rate, may be prone to photoinhibition and is carbohydrate supply (i.e., source) limited when compared to other temperate fruit crops.