Anatomy of the Vegetative Organs of the Pineapple, Ananas comosus (L.) Merr. (Continued) II. The Leaf

Abstract

In the literature, the leaves of Bromeliaceae are known to possess many anatomical features which are peculiarly characteristic of the family. The species A. comosus exhibits excellent illustrations of these features. The anatomical modifications which make for the xerophytic behavior of the pineapple thick-walled epidermal and hypodermal cells, a thick water-storage tissue, stomata in furrows on the lower side of the leaf only and a thick mat of trichome heads covering the stomata, are described. The trichomes of this species function primarily as deterrents to excessive transpiration rather than to absorb water as in many other bromeliaceous species. Protection to the long narrow leaf against bending and tearing is furnished by the intimate interlocking of thick-walled epidermal and hypodermal layers and by fiber strands. Interesting features described are the aerating canals, silica bodies in the epidermal cells, the endo-dermis-like sheath of vascular bundles, diurnal phases of chloro-plast structure, and previously unreported juvenile form of filiform hair.