Changements cytochimiques et ultrastructuraux des parois cellulaires de la pellicule du raisin, Vitis vinifera, durant la croissance et la maturation de la baie

Cytochemical and ultrastructural analysis of cell wall characteristics was performed in the dermal system of the grape berry (Vitis vinifera L. cv. Pinot noir), using a test for polysaccharides (periodic acid – thiosemicarbazide – silver proteinate, associated with dimethylsulfoxide extraction). Samples were examined at successive stages of fruit development. The main events of the first growth phase, i.e., thickening of hypodermal cell walls and their tangential extension, continued during the second growth phase. At all the stages of grape development, tangentially expanding walls were typical of actively growing plant cell walls, with an ordered texture, new layer deposition, and progressive rotation of microfibrillar subunits (bow-shaped patterns). At maturity, hydration, swelling of the walls, and an increase in the amount of soluble pectic substances were noticed. No redifferentiation of the cell walls occurred. The cuticle, already differentiated into two layers at the first growth phase, was clearly lamellar during the second. At maturity a number of layers, distinguishable by their cytochemical reactivity, were detected. Cuticle thickness increased during "véraison" and was maintained throughout the second growth phase. A considerable increase in the content of epicuticular waxes was noticed during ripening.