Observations on the distinctive cream-coloured leaves of Combretum nelsonii Dümmer

The ultrastructure of the cream-coloured leaves subtending the flowers and of the leaves of Combretum nelsonii, is described. The cream leaves, which are shed as the fruits mature, lack functional plastids within the irregularly-shaped palisade, although the spongy mesophyll cells are photosynthetically active. Abundant air-spaces below the papillate upper epidermis and between the palisade cells cause light to be refracted within the cream leaves, contributing to their pale colour. Cream leaves do not regreen but become obscured by younger green leaves

An antogenetic study with special reference to leaf development in C3 and C4 forms of Alloteropsis semialata.

This ontogenetic study conducted at light and electron microscope level, describes several aspects of leaf development in C3 and C4 forms of Alloteropsis semialata. Emphasis is placed on the distribution and anatomy of vascular bundles as seen in transverse sections. The derivation of the specialised photosynthetic tissue of the Kranz sheath, which characterises the C4 form is, traced in the inner of mestome layer of the double bundle sheath. The lamina and sheath in successive leaves of comparable age in the two forms were used. The proportion of photosynthetic tissue present in sections taken at midlamina is assessed quantitatively using a planimeter. The main conclusions drawn from this study are summarised as follows: 1. Lamina and sheath in leaves of A. semialata, in common with other grasses, are derived from different meristems, show different patterns of vasculatization and mature at different rates, the tip representing an older portion of the leaf than the base; 2. The differences in the bundle sheath anatomy between C3 (non-Kranz) and C4 (Kranz) forms of A. semialata are more obvious in the lamina than in the colourless sheath, and 3, the proportion of chlorenchymatous tissue is higher in the C4 than in the C3 leaf.Keywords: alloteropsis semialata; anatomy; c3 grasses; c4 grasses; development; grasses; leaf development; leaves; south afric