Abstract/Summary:
Epidermal ultrastructure and cuticle development were investigated in leaves of the xeromorphic Australian shrub, Hakea suaveolens. The heavily cutinized outer epidermal wall consists of seven distinct layers. The cuticle proper is an up to 1.5µ thick zone of alternating electron dense and translucent lamellae. The distinctness of the individual lamellae is related to their ontogeny and probably to their synthetic activity. The lamellae are believed to be involved in synthesis of epicuticular wax. A reticulate cuticular layer starts to develop before expansion has ceased. The production in spherosomes and transport through the walls of wax- and cutin precursors are shown at different stages. Vesicles containing fibrillar material are seen discharging their content to the wall. Short, 50 nm thick membrane tubuli are found outside the plasmalemma. Ectodesmata are demonstrated after Gilson fixation as well as after glutaraldehyde/osmium tetroxide fixation. They proved to be extensions of the innermost wall layer having a high content of pectins. Epidermal structure is discussed in relation to the concept of xeromorphy.