Changes in Photosynthesis and Respiration during Berry Development in Relation to the Ripening of Delaware Grapes

Abstract

The relationship between berry growth and changes in respiratory rate and photosynthetic CO2-assimilation rate during the development of grape berries and seeds was studied in relation to their ripening.(1) The respiratory rate of berries in terms of dry weight basis became high at an early part of Stage I and thereafter decreased rapidly. When expressed on a single berry basis, the respiratory re ate increased rapidly during Stage I through Stage III, but there was a sudden drop at veraison.(2) The rate of gross-photosynthesis expressed on a dry weight basis showed its peak during the early part of Stage I and decreased rapidly thereafter. When expressed on a single berry basis, the rate of gross-photosynthesis showed two peaks, i.e., later part of Stage I and early part of Stage III.(3) The respiratory rate per seed showed its peak at the onset of Stage II. While, the rate of respiration on a dry weight basis was highest at Stage I and rapidly decreased thereafter.These results led to an assumption that the photosynthetic activity of berries may affect their development markedly at early stages of growth, and the second peak of respiration and gross-photosynthesis may play an important physiological role in controlling the onset of their ripening.