As an approach to the analysis of components associated with the production of high quality fruit of Muscat of Alexandria grapes (Vitis vinifera L.), seasonal changes in the growth rate, dry matter accumulation, and CO₂ evolution from clusters, and the apparent rate of photosynthesis in leaves were investigated throughout the growing season.
1. The increment of cluster volume exhibited a typical double sigmoid curve. The ratios of cluster volume increase were 37% in the stage I, 19% in the stage II, and 44% in the stage III, respectively, of mature clusters. Dry matter accumulation followed a simple sigmoid curve, the ratios being 11%, 17%, and 72% in stages I, II, and III, respectively. The accumulation in stage III was most significant.
2. Percentage of dry matter in clusters decreased rapidly from the stage of full bloom, became minimum at the end of stage I, and then increased linearly thereafter.
3. CO₂ evolution from clusters on fresh weight basis increased linearly for the first 6 days from the full bloom and decreased drastically thereafter. CO₂ evolution per cluster, on the other hand, showed 2 peaks, one at the transition point from stage I to stage II, and another at the early phase of stage III.
4. The ratios of amounts of dry matter translocated into clusters, the sum of accumulated dry matter and glucose equivalent dry matter calculated from CO₂ evolved, were estimated to be 13%, 20%, and 67% in stages I, II, and III, respectively.
5. The apparent rate of photosynthesis in leaves increased gradually and reached a maximum at about 1 month from the leaf expansion, about at blooming stage, and decreased thereafter due to low light intensity during the rainy season. It increased again for some time during the stage II, and then decreased gradually until leaf fall.
6. The seasonal pattern of apparent photosynthesis was different from that of dry matter accumulation. The translocation of photosynthate into clusters became maximum in stage III, while photosynthetic ability of leaves was in the process of gradual decrease. Based on these results, it was inferred that overloading of fruits in this stage result in an inhibited growth, delay of maturation, and low sugar content in mature berries.