PARTITIONING OF C-14 PHOTOSYNTHATE IN DEVELOPING KIWIFRUIT

Kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cultivar 'Hayward') leaves were allowed to photosynthesise 14CO2 and the fate of the photosynthate in different tissue zones of the fruit was studied at various stages of fruit development. Photosynthate moved into the fruit at all stages of fruit development examined (February, April, May). Proportionally more photosynthate was allocated to the core in May than in February. In May, a greater proportion of radioactive photosynthate was found at the stem end of the fruit than in the blossom end of the fruit. There was a diurnal pattern of incorporation of label into the insoluble residue and organic acid fractions in all tissues in February. Both the proportion and amount of radioactivity incorporated into the insoluble residue and organic acid fractions decreased as the fruit matured. The results support the concept that the core is metabolically more active than the inner cortex at late stages of fruit development, and indicate that the different concentrations of quinic and citric acids found in each tissue are not due to different rates of metabolism of photosynthate within the tissues. Evidence is given that the greater concentration of soluble solids occurring at the blossom end rather than the stem end of the fruit in April and May is not caused by incoming photosynthate. © 1990.