C₄ Acid Decarboxylation Enzymes and Anatomy in Sedges (Cyperaceae): First Record of NAD-Malic Enzyme Species

Abstract

The activities of C₄ acid decarboxylation enzymes (NAD-malic enzyme, NADP-malic enzyme, and phosphoenolpyruvate carboxykinase), and the anatomy of photosynthetic organs (leaves, culms, bracts) were investigated in 30 species from 12 C₃, C₄, and mixed (C₃+C₄) genera of sedges. The sample incorporated representatives of the three previously known C₄ anatomical types in the family (fimbristyloid, chlorocyperoid, and rhynchosporoid), and of six genera previously uninvestigated biochemically, including Eleocharis (six species). Eleocharis is variable for photosynthetic pathway: three species proved to be C₃, two C₄ (E. caespitosissima Baker and E. retroflexa (Poir.) Urban), and one (E. pusilla R. Br.) may be a C₃-C₄ intermediate. The C₄ Eleocharis spp. exhibit a C₄ anatomy ('eleocharoid') hitherto undescribed, and are NAD-ME type, in contrast to species of the other three C₄ anatomical types examined in this and previous studies, which are all NADP-ME type. The PCK type remains unrecorded in the family.