Leaf anatomy of the South African Danthonieae (Poaceae). IX Asthenatherum glaucum

Abstract

The leaf blade anatomy of Asthenatherum glaucum (Nees) Nevski was studied. Detailed descriptions of the leaf section and abaxial epidermis are given and illustrated by means of photomicrographs. The leaf anatomy of all specimens is undoubtedly Kranz with radiate chlorenchyma and specialized parenchyma bundle sheath chloroplasts. This observation is the most important justification for separating Asthenatherum from Danthonia, which has non-Kranz anatomy.

Significant epidermal variation was observed, particularly in the form and occurrence of macro-hairs and prickles. These epidermal differences appear to correlate with geographical distribution and growth form of the plants and may be of infraspecific taxonomic significance. The epidermal variation is continuous, but three more or less distinct groups can be recognized: annual plants with unique macro-hairs with corrugated walls; annual or perennial plants without macro-hairs but with large straight prickles without swollen bases; and perennial plants without these large prickles. These groups appear to represent an intergrading cline along an increasing moisture gradient eastwards from the Namib Desert in South West Africa/Namibia.