LEAF ANATOMY, EMPHASIZING UNUSUAL CONCERTINA MESOPHYLL-CELLS, OF 2 EAST-AFRICAN LEGUMES (CAESALPINIEAE, CAESALPINIOIDEAE, LEGUMINOSAE)

Cordeauxia edulis (Somalia and Ethiopia), and Stuhlmannia moavii(Tanza nia, Kenya and Madagascar) are evergreen shrubs or small trees of dry areas. They have similar leaf anatomy as revealed by resin sectioning and scanning electron microscopy. The cuticle is extremely thick and a ll vascular bundles lack bundle sheath extensions. The most unusual fe ature is the mesophyll, three to seven layers consisting entirely of c ylindrical palisade cells with lateral walls capable of changing verti cal length by folding in a concertina-like manner. The matching outwar d folds of two adjacent cells always remain attached by means of a row of wall thickenings ('pegs'). The pegs can elongate, especially so be tween the widely separated mesophyll cells that occupy the substomatal chamber area. The unattached flexible inward wall folds enable these 'concertina' cells to shorten or lengthen vertically without disruptin g cell interconnections in the interior of each relatively long-lived leaf as it periodically loses and gains water. Concertina cells may be an anatomical adaptation allowing these leaves to remain evergreen an d survive extended periods of drought and yet to store water quickly w hen it becomes available. (C) 1996 Annals of Botany Company