Towards a comprehensive survey of C₃ and C₄ photosynthetic pathways in Cyperaceae

Members of the family Cyperaceae were surveyed by original observation and from the literature to assess the distribution of C₃ and C₄ photosynthetic pathways in the family. All 107 genera were included in the current sample, with 91 genera assessed as consistently C₃ and 11 genera as C₄. The genera 'Abildgaardia', 'Cyperus', 'Eleocharis',' Fimbristylis', and 'Rhynchospora' are variable for this trait. Of the total number (1474) of specific (1406) and infraspecific (68) taxa sampled, 938 taxa (63%) are C₃, 527 taxa (36%) are C₄, and nine species of Eleocharis are debatably intermediate or variable in pathway. Some data suggesting further infrageneric variation in photosynthetic pathways are discussed. The "one cell distant criterion" accurately predicts C₄ pathway in sedges, except in Eleocharis. Distribution and variability of photosynthetic pathways in Eleocharis are discussed. Photosynthetic pathway was found to be a useful taxonomic marker in Cyperaceae, despite variability in this trait at various taxonomic levels and the apparently multiple origin of C₄ photosynthesis within the family. A checklist of 3395 records of C₃ and C₄ sedges is presented.