Structural features of NAD-malic enzyme type C₄ Eleocharis: An additional report of C₄ acid decarboxylation types of the cyperaceae

The genus Eleocharis, a blade-less sedge group, has been very recently recorded to include NAD-malic enzyme type C₄ species. The ultrastructural features of culms of two C₄ representatives in the genus were examined in relation to the C₄ acid decarboxylation type. They possessed non-chlorophyllous mestome sheath cells between mesophyll cells and Kranz cells, and were confirmed biochemically to be NAD-malic enzyme type. The oval or lenticular chloroplasts with well-developed grana are scattered in the Kranz cells with abundant large mitochondria, and do not show such centripetal position as is known in the "classical NAD-malic enzyme type". The suberized lamellae occur in the mestome sheath cells internally surrounding the Kranz sheath and may contribute to maintaining high CO₂ concentration in the Kranz cells. These new structural features of the NAD-malic enzyme type found in Eleocharis are added to the structural and functional relationships of the C₄ types in the Cyperaceae reported previously