Ultrastructure of Cuticular Surfaces and Stomata of Developing Leaves and Fruit of the ‘Valencia’ Orange1

Abstract

Abstract The outer stomatal openings on Citrus sinensis cv. Valencia fruit and leaves were formed by rupturing of the cuticle and possibly some of the outer epidermal cell wall. Small, 5µ diam, structures surrounded by wax were visible on the young fruit surface. The wax on immature fruit was soft, forming a continuous film with little surface structure. With maturation the progressive formation of more and harder epicuticular wax resulted in more visible structure. The eventual cracking and lifting of the wax film indicated loss of its ability to expand with the slow developing cuticle - cell wall complex. Leaves developed some surface wax structure but no platelet wax was formed. The leaves expanded rapidly and the leaf surface wax remained soft during this time.