The accumulation of tannins during the development of ‘Giombo’ and ‘Fuyu’ persimmon fruits

• Tannin cells are already present at the stage of flower bud appearance.
• A sequence of events tannin accumulation in cells is proposed.
• The patterns of accumulation of tannins are similar in both cultivars.
• The astringency is related to cell tannin density and soluble tannins.
• Persimmons ‘Giombo’ exhibit high levels of soluble tannins to maturity.

Tannins are responsible for the astringency of persimmon fruits. The present study compared the development of ‘Giombo’ (PVA) and ‘Fuyu’ (PCNA) persimmon fruits until maturity to determine if the difference in astringency between the two cultivars is related to the early accumulation of tannins in the cells or to differences in the pattern of tannin accumulation during cell differentiation, cell density or the concentrations of total and soluble tannins. Persimmon flowers and fruits were collected from a commercial orchard in Mogi das Cruzes during the 2010–2011 harvest season at predetermined stages until the fruit reached commercial maturity. Structural analyses were performed by light, scanning and transmission electron microscopy, and quantitative analyses of tannin cell density, tannin cell index and total and soluble tannins were also performed. In both cultivars, the ovary already exhibited a small number of tannin cells. Throughout development, the ‘Giombo’ persimmon possessed higher tannin cell density and higher levels of total and soluble tannins compared to ‘Fuyu’. The accumulation of tannins in the cells was homogeneous and restricted to the vicinity of the cell wall, in spherical vesicles connected to the tonoplast, as amorphous distributions occupying the entire vacuole, as homogeneous distributions with circular, unfilled areas in vacuoles, and as homogeneous distributions that completely filled the vacuoles. At the end of fruit development, the parenchyma cells displayed large intercellular spaces and degraded pectins, indicating fruit ripening and senescence.