Occurrence of the Suberized Lamella in Leaves of Grasses of Different Photosynthetic Type. II. In Herbarium Material

Abstract

Dead air-dried leaves have been conventionally prepared for transmission electron microscopy to ascertain if the occurrence of a suberized lamella in cell walls can be detected. Our species sample includes representatives of all known photosynthetic types within the Poaceae (viz. C₃, C₄ NAD-malic enzyme type, C₄ NADP-malic enzyme type and PEP carboxykinase type). Each photosynthetic type exhibits a characteristic pattern of suberized lamella occurrence in mestome sheath and/or 'photosynthetic carbon reduction' (PCR or 'Kranz') cell walls, consistent with that in fixed living material. Plasmodesmatal structure, and even on occasion chloroplast structure, is remarkably well preserved. Leaves from herbarium specimens, therefore, could be used to assign C₄ species to their C₄ acid decarboxylation type. This has potential application in large-scale systematic surveys for which living material may be difficult to obtain.