EFFECT OF TIME OF DAY, A PARASITIC FUNGUS, AND A GENETIC MUTATION ON RATE OF PHOTOSYNTHESIS IN THE LOWBUSH BLUEBERRY

Abstract

The apparent rate of photosynthesis in the lowbush blueberry was measured, at four periods of the day, on leaf disks in Warburg flasks and with the use of Pardee's CO2 buffers. Significant differences were found in rates of O2 evolution at the four different periods. Oxygen evolution was greatest in the early morning when reducing sugars and starch levels were lowest. By early afternoon when starch and reducing sugar levels were much greater in the leaf disks the rate was the lowest.Leaf disks infected with Exobasidium vaccinii had a lower rate of apparent photosynthesis than normal leaves of the same clone. Disks cut from normal leaves of Vaccinium angustifolium had a higher rate of apparent photosynthesis than those of a variegated mutant. The leaves of the mutant were significantly smaller and seedlings of the mutant type grew more slowly than normal ones of the same cross. For these reasons lowbush blueberry plants of the mutant type or having the red-leaf disease are at a distinct disadvantage in nature.