Distribution of ¹³C Administered to a Leaf of a Bearing Shoot of Fig Trees during the Fruit Enlargement and Maturation Stages at the Lower Nodes

Abstract

Leaves at different bearing nodes on current shoots of seven-year-old 'Masui Daufine' fig (Ficus carica L.) trees cultivated in a greenhouse were exposed to ¹³CO₂ during the fruit enlargement and maturation stages at lower nodes. After one week of exposure to ¹³CO₂, the distribution of ¹³C-photosynthate in fruit-bearing shoot was investigated. The results were as follows : 1. When the 3rd leaf was treated during fruit set and enlargement period at lower nodes, some of the ¹³C-photosynthates was assimilated by the treated leaf, while a large portion went to the developing young fruit in its axis ; the remainder was partitioned to the adjacent lower stem. Similarly, when ¹³CO₂ was applied to the 6th leaf, much of the ¹³C-photosynthates remained in the leaf ; the rest was exported to young fruits, inflorescences, leaves, and shoots at the upper and lower nodes. When the 9th leaf was treated, it retained more of the ¹³C-photosynthates than did the immature fruit in its axis ; a significant amount was retained in the adjacent upper part of the shoot. The ¹³C accumulation data revealed that the fruit in Stage I had a greater sink strength than had the developing inflorescences. 2. When the fruit on the 5th node was treated with oil one week before harvest (August 3, 1998) to induce early maturity, it showed a highly active sink, importing ¹³C-photosynthates primarily from leaves on the 3rd to the 7th nodes.