STRUCTURE OF XEROPHYTIC PLANTS FROM SOUTHERN AFRICA. LEAF ANATOMY OF ANTIZOMA MIERSIANA AND DIOSPYROS RAMULOSA

ABSTRACT

An anatomical investigation of the leaves of Antizpma miersiana (Menispermaceae) and Diospyros ramulosa (Ebenaceae), both xerophytic, woody evergreen species, was conducted. Specimens were collected in the arid regions of Namaqualand in southern Africa. A number of classical xeromorphic features are present in A. miersiana, namely thick, cutinized outer epidermal cell walls, a thick epicuticular wax layer, sunken stomata, and mesophyll tissue consisting of a number of palisade parenchyma layers. Two notable features are papillose epidermal cells and large secretory cavities in the mesophyll or associated with the vascular bundles. The leaves of D. ramulosa do not exhibit many features which may be regarded as xeromorphic. An obvious feature of this species is the occurrence of phenolic deposits in the mesophyll and epidermal cells. The leaf anatomy is discussed in relation to its ecological significance.