Anomalous vascular bundle sheath structure in Alloteropsis semialata leaf blades

Abstract

Alloteropsis semialata (R.Br.) Hitchc. of the Paniceae, would be expected to exhibit typical eupanicoid leaf anatomy with a single bundle sheath of large parenchymatous cells with specialized
chloroplasts and radially-arranged chlorenchyma. Specimens from South Africa showed the following bundle-sheath and mesophyll deviations from the generalized panicoid model: 1. bundle
sheath is double; 2. inner bundle sheath is composed of large cells with specialized chloroplasts; 3. outer sheath consists of many smaller cells with few, or without chloroplasts; 4. outline of the third-
order bundles is tall and narrow; 5. chlorenchyma is not radially arranged. Other specimens of A. semialata, however, were found to have a large-celled outer bundle sheath devoid of chloroplasts
and with indistinctly radiate chlorenchyma.