Growth inhibition of persimmon fruit caused by calyx lobe removal and possible involvement of endogenous hormones

Growth inhibition of persimmon fruit (Diospyros kaki L.) was induced by calyx lobe removal in the middle of growth stage I (13 July) or at the beginning of stage II (24 August), but no inhibition was observed in the treatment at growth stage III (2 October). Lobe removal at stages I and II resulted in fruit weight reduction of 44% and 76% of the controls, respectively. Coincident with growth inhibition of the treated fruits, the ratio of sucrose to hexoses (glucose and fructose) increased significantly in the flesh, indicating an unsuitable gradient for further import of the sucrose into the sink organs. The effects of calyx lobe removal on endogenous gibberellin (GA)-like substances and abscisic acid (ABA) content were also investigated. Growth inhibition was not related to changes in the activity of endogenous GA-like substances. However, a significant decrease of ABA content after calyx lobe removal at growth stage I or stage II may suggest its involvement in growth inhibition of persimmon fruit. Possible mechanism of growth inhibition by calyx lobe removal was also discussed focusing on sugar metabolism.