Distribution of Lithocysts, Trichomes, Hydathodes and Stomata in Leaves of Pilea cadierei Gagnep. & Guill. (Urticaceae)

Abstract

In leaves of Pilea cadierei lithocysts, trichomes and hydathodes in the upper epidermis, and lithocysts, trichomes and anomocytic stomata in the lower epidermis are components of a regular distribution pattern in which spacing probably depends upon inhibitory interactions between initial cells during leaf development. Anisocytic stomata, which also occur in the lower epidermis, show a clumped distribution pattern that results from their relatively late formation after cell division in the epidermis is otherwise complete, and from the inhibitory influence of established lithocysts, trichomes and anomocytic stomata. Ordered spacing of anisocytic stomata within groups probably results from mutual inhibition between initial cells at the time of inception. Lithocysts associated with primary and secondary veins are elongated along the vein axis. Elsewhere in the leaf lithocyst, orientation is oblique relative to the midrib and shows a correlation with vein orientation around the time of lithocysts elongation.