Effect of Growth Habit of Bearing Shoot on the Distribution of 13C-Photosynthates in Kiwifruit Vines

Distribution patterns of 13C-photosynthates in bearing kiwifruit vines in relation to shoot growth were investigated in June and July. The amount of 13C from leaves partitioned into fruit was greater in naturally self-pinched shoots than it was in growing shoots at early and mid-stages of fruit development. At 120 hours after 13CO2 feeding in June, 13C contents were 11.1 and 1.2mg per fruit, for self-pinched and growing shoots, respectively. A steep gradient in 13C concentration from the base to the apex of the growing shoots existed, whereas there were little differences in 13C levels among the nodal positions in self-pinched shoots. Furthermore, fruit had more 13C 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 natural self-pinching and manual pinching to suppress shoot extension are effective means for favoring the allocation of photosynthates to fruit so as to promote their growth and development.