Morphological Development and Chemical Composition of Epicuticular Wax Crystals in 'Campbell Early' Grape

Abstract

To study the development of epicuticular wax crystals (EWCs) in 'Campbell Early' grape during growth period, the berry surface was examined using a scanning electron microscope. Because EWC was not developed at Cull bloom, ovary was only covered with cuticular ridges, and these existing cuticular ridges were split without additional formation of cuticular ridges along with the ovary enlargement through rapid cell divisions. Six days after full bloom (DAFB), EWCs began to be observed between the interstices where cuticular ridges were split and could be identified by naked eyes at 18 DAFB. The appearance of fully developed EWCs was like platelets, and there were little changes in their basic forms at 18 DAFB. At 34 DAFB, EWCs were filled up more densely in the spaces between existing EWCs than those at 18 DAFB. and the surface area covered with EWCs also became larger. After this period, the pattern of EWCs was changed like lace shape along with the size enlargement. The part of their edges was changed gradually to the sharp pattern from the initial dull pattern, and the amount and size of platelets were increased continuously. The result also showed that the pattern of EWCs was retained even after harvest. Epicuticular wax (EW) consisted of all aliphatic compounds including alkalies, alkenes, primary alcohols, aldehydes, esters, and fatty acids. The major compounds of EW were heptadecanoic acid ethyl ester (25.7 +/- 037%), octadecanoic acid ethyl ester (24.5 +/- 0.86%), and octadecane (22.7 +/- 2.06%).