Effects of calcium compounds on fruit puffing and the ultrastructural characteristics of the subepidermal cell walls of puffy and calcium-induced non-puffy satsuma mandarin fruits

The alleviating effects of calcium compounds on fruit puffing were investig ated in satsuma mandarin. The ultrastructural changes in the subepidermal c ell walls of puffy fruits and the inhibiting strategies of calcium against these changes were also observed under transmission electron microscope. Al though puffing occurred in both treated and non-treated fruits under certai n environmental conditions, pre- harvest applications of CS - 2H (CaSO4 . 2 H(2)O, CaCl2) and CS-1B (CaCO3 microcrystal suspension) significantly reduc ed it and with the exception of peel puffing these chemicals did not affect other fruit characteristics. The subepidermal cells of nontreated puffy fr uits had bigger intercellular spaces in the cell corners and schizogenous i ntercellular spaces between adjacent walls. Occasionally, cell corners and abutting walls did nor possess these spaces, but the disintegration of midd le lamella therein was distinct. The disintegration caused loosening of the intercellular connection and swelling of walls. The sporadic destruction o f the cell wall was also found near the plasma membrane. The fibrillar mate rials of loose cell walls separated distinctly in the longitudinal directio n; this separation was crosswise near the plasma membrane. In a few cases, the middle lamella and its adjoining walls had disintegrated. The applicati on of calcium compound (CS-2H) prevented these ultrastructural disorders so that intercellular spaces remained small, schizogenous intercellular space s did not develop, and the dissolution of middle lamella was checked consid erably. The cell corners retained their middle lamella or sometimes develop ed small intercellular spaces. The fibrillar materials in the cell walls we re compact and their destruction was not evident. Cell wall swelling was ra rely observed, and cellular separation was not found.