1980 Volume 48 Issue 4 Pages 405-412
Effect of shading to Delaware grape clusters with different materials was investigated in respect to sugar accumulation and free acid decrease in the berries during their development. Sugar accumulation as affected by abscisic acid (ABA) application to the cluster, and changes in 14CO2 fixation by the berries under light and dark conditions were also studied.
(1) In the Stage I, the concentration of reducing sugar was little affected by different light intensity, while that of free acid in 50% of light intensity was significantly less than that in 0%, 10%, 20% and 100% during the period of free acid accumulation in the berries. Higher light intensity in the Stage III resulted in higher reducing sugar content at harvest if it did not exceed 50% of light intensity. But, free acid content was little affected. When the dark treatment of the clusters was intercepted during Stage III, the concentration of reducing sugar in the berries increased very rapidly.
(2) Application of 50% ethanol solution of ABA (1, 000ppm) to the cluster at late Stage I accelerated the accumulation of reducing sugar in the berries. Although anthocyanin content of the berries was increased by such a ABA application to the cluster under dark, the reducing sugar content was not affected.
(3) Assimilation of carbon dioxide brought by the berries themselves was found both under the light and dark conditions. In the light, a rapid increase in photosynthetic fixation of carbon dioxide was observed in the beginning of stage I, and the beginning and middle of Stage III. 14C activity at the former stage was found relatively uniform in sugar, organic acid and amino acid fractions. But, it was 90% or more urder sugar fraction at the latter stage. Most of 14C activity in the dark fixation was found in organic acid and amino acid fractions at any stages of berry development. However, the amount of 14C activity incorporated in the dark fixation was much lower than that in the light fixation.
