C₄ photosynthesis and a unique type of Kranz anatomy in Glossocordia boswallaea (Asteraceae)

Abstract

A special form of Kranz anatomy, a single chlorenchymatous bundle sheath around a central ground tissue embedding the vascular bundles, was observed to be associated with the C₄ pathway of photosynthesis in Glossocordia boswallaea, a member of Asteraceae. The chloroplasts were centripetally located in the sheath cells. During short term carbon fixation, C₄ acids, aspartate and malate were predominantly labelled. Radioactivity was transferred from aspartate to sugar phosphates, sucrose and starchvia phosphoglyceric acid. Enzyme activities in the leaves revealed that the plant is an aspartate forming NAD malic enzyme type. The activities of both photosystems I and II were detected in mesophyll as well as the bundle sheath chloroplasts. The findings are discussed in relation to its tropical habitat.