Fruit respiration for maintaining sink strength during final swell at growth stage III of persimmon fruit

Persimmon fruit shows a rapid increase in fruit respiration with the onset of final swell at growth stage III. To investigate the role of this respiration rise in provoking sink strength at growth stage III of persimmon fruit, the accumulation of ¹³C-photoassimilate was determined during growth stage III comparing the control fruit and the fruit whose calyx lobes were removed with or without sealing their scars with 'Vaseline'. Fruit respiration was not affected by calyx lobe removal alone. By sealing the scars with 'Vaseline' after calyx lobe removal, however, fruit respiration was markedly inhibited. Inhibition of fruit respiration by calyx lobe removal and sealing the scars with 'Vaseline' decreased fruit growth, but at least one week was needed to detect a significant decline in fruit diameter. Contrarily, inhibition of fruit respiration induced an immediate reduction in ¹³C-photoassimilate accumulation into the fruit which preceded the reduction in fruit diameter. The inhibition of fruit respiration seemed to reduce the sink strength of the fruit, which in turn suppressed fruit growth. In spite of this remarkable reduction in fruit sink strength by inhibiting fruit respiration, sugar content and/or composition in the fruit showed no differences between treated and control fruit. We concluded that the high respiration during growth stage III in persimmon fruit is important for maintaining sink strength for the final swell of fruit.