LEAF ANATOMY OF CONOPHYTUM N. E. BR. (AIZOACEAE)

Abstract

Leaf anatomy of Conophytum–a genus of 100 species of miniature xerophytic plants from the succulent Karoo in southern Africa–was examined using thin sections of plastic-embedded tissue and bright-field and polarized-light microscopy. Eighty-four species, from all recognized sections of the genus, were sectioned using material of known wild origin, with many species represented by multiple infraspecific taxa or populations. The broad scope of this investigation permits, for the first time, a meaningful study of the comparative anatomy of this large, morphologically diverse genus. The distribution of anatomical characters is described including: the pattern of deposition of calcium oxalate crystals in the epidermis, the presence and number of layers of hypodermis, and the presence and shape of tanniniferous idioblasts in the mesophyll. Typically xeromorphic characters like a hypodermis and epidermal crystal layers tend to be reduced or absent in species from sheltered niches, including soil-embedded, subterranean species with windowed leaves. Embedded species also frequently lack tannin cells, perhaps because their growth form reduces the need for chemical defenses against herbivores.