Morphological Characteristics of Tannin Cells in Japanese Persimmon Fruit

Abstract Tannin cells from fruit of Japanese persimmon ( Diospyros kaki L.) cvs. Fuyu [pollination-constant and nonastringent (PCNA)], Chokenji [pollination-variant and nonastringent (PVNA)], Hiratanenashi [pollination-variant and astringent (PVA)], and Kuramitsu [pollination-constant and astringent (PCA)], were observed by florescence microscope (FM) and scanning electron microscope (SEM) on 4 July, when all cultivars were very astringent, and on 5 Sept., when ‘Fuyu’ and ‘Chokenji’ fruit had completely lost their astringency. ‘Hiratanenashi’ and ‘Kuramitsu’ fruit, however, were still quite astringent on the latter date. FM observations on 4 July indicated that tannin cells of all fruit possessed some discontinuous portions in the cell walls. SEM observations of fractured surfaces of fruit flesh verified the existence of pores in the tannin cell walls. Moreover, coagulated internal contents of tannin cells (caused by the fixatives) had protruded through the pores. On 5 Sept., however, the pores in tannin cell walls of ‘Fuyu’ and ‘Chokenji’ were not present, and the surface of coagulated internal contents had become smooth. ‘Hiratanenashi’ and ‘Kuramitsu’ fruit on 5 Sept. showed little change in the structure from that observed on 4 July. Pore occlusion occurred in ‘Hiratanenashi’ fruit that were treated on the tree with ethanol fumes to remove astringency, which indicates that loss of astringency induces structural changes in tannin cell walls.