Inflorescence and floral characters indicating C3 and C4 photosynthesis in some species of the genus Cyperus L. (Cyperaceae)

Abstract

Inflorescence and floral morphological characters in twelve species of Cyperus – a genus  known to have C₃ and C₄ photosynthetic species – were investigated in order to check their usefulness in delimiting species into photosynthetic groups. Plant species were collected from different locations within Southwestern Nigeria. Qualitative characters were noted and recorded while some quantitative characters were measured with metric ruler to the nearest centimeter and others were counted. The results revealed that compound umbellate inflorescence, digitately arranged spikelets and short spikelets not over 1cm long are  characters that separate C. difformis and C. haspan which are C₃ species, while the rest with simple umbellate inflorescence, spicate spikelets and spikelet length over 1cm are C₄ species. Cyperus dilatatus, a species without a previous record of photosynthetic grouping, is hereby grouped as a C₄ species since it shared characters with the rest C₄ species. From this study, a combination of characters was identified, which can possibly be used along with known data from other sources in the grouping of Cyperus species as either C₃ or C₄ species. Data on C. dilatatus also showed that it possibly belong to C₄ species. This is probably the first known  report on photosynthetic grouping of this species.

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Keywords: C₃ - C₄ species, Cyperus genus, inflorescence morphology, photosynthetic grouping, taxonomy