DEVELOPMENT AND HISTOCHEMISTRY OF THE CELLS, CELL-WALLS, AND CUTICLE OF THE DERMAL SYSTEM OF FRUIT OF THE GRAPE, VITIS-VINIFERA L

The dermal system comprises the outer epidermis of the pericarp, its covering of wax and cuticle and the collenchymatous hypodermal cells. During the 1st of the 2 post-anthesis phases of fruit growth, differentiation occurred with respect to cell and nuclear volume, content of polyphenolic substances and wall thickening. Walls of the presumptive dermal system cells developed massive primary thickenings which stained intensely with fluorescent brightener dyes. In the 2nd phase of fruit growth these cells were redifferentiated, their walls becoming thinner as they enlarged to accomodate fruit expansion. Binding of the fluorescent brightener dye was reduced and confined to the outer edges of the walls. At maturity the walls of the cortical cells adjacent to the dermal system underwent autolysis. The cuticle was evident during the 1st 16 days after anthesis as a thin layer which reacted positively with neutral lipid dyes and which contained periodate sensitive vinyl groups. Differentiation of a secondary cuticle followed, and a number of distinct layers were detected by autofluorescence and staining with auramine O, Nile blue and PAS [periodic acid-Schiff]. Cuticle thickness and complexity were maintained throughout the 2nd growth phase.