EFFECT OF GROWTH HABIT OF BEARING SHOOT ON THE DISTRIBUTION OF C-13-PHOTOSYNTHATES IN KIWIFRUIT VINES

Distribution patterns of C-13-photosynthates in bearing kiwifruit vine s in relation to shoot growth were investigated in June and July. The amount of C-13 from leaves partitioned into fruit was greater in natur ally self-pinched shoots than it was in growing shoots at early and mi d-stages of fruit development. At 120 hours after (CO2)-C-13 feeding i n June, C-13 contents were 11.1 and 1.2 mg per fruit, for self-pinched and growing shoots, respectively. A steep gradient in C-13 concentrat ion from the base to the apex of the growing shoots existed, whereas t here were little differences in C-13 levels among the nodal positions in self-pinched shoots. Furthermore, fruit had more C-13 than did the terminal parts of shoots, including leaves in self-pinched shoots, but the reverse was true in growing shoots. These results show that shoot elongation during fruit growth adversely affects the distribution of photosynthates into fruit. Therefore, such practices as inducing natur al self-pinching and manual pinching to suppress shoot extension are e ffective means for favoring the allocation of photosynthates to fruit so as to promote their growth and development.