Do Melastomataceae perform CAM photosynthesis? A survey of neotropical species using carbon isotope ratios

Abstract

Abstract:Leaf anatomical and carbon isotope ratio (δ13C) data from previous studies suggest that the species of the Melastomataceae perform C3 photosynthesis and that leaf anatomical features of some epiphytic taxa resemble the characteristics found in CAM plants. The δ13C values of 67 species of neotropical Melastomataceae (including epiphytes) were obtained from herbarium material deposited at the California Academy of Sciences for assessing the presence of the CAM pathway. The δ13C values obtained from leaves (−23.4‰ to −34.5‰) were congruent with C3 photosynthesis (< −20‰), and the δ13C data from terrestrial (56 samples) and epiphytic species (11 samples) were not statistically different. Our results suggest that CAM photosynthesis is not found in neotropical Melastomataceae. The leaf anatomical features found in some species of Melastomataceae represent adaptations to cope with water stress and are not necessarily correlated with CAM photosynthesis. Photosynthetic pathways can be assessed with the use of leaf anatomical and δ13C data, but further biochemical assays are warranted to corroborate the absence of the CAM pathway in the Melastomataceae.