Photosynthetic pathway variation among C₄ grasses along a precipitation gradient in Argentina

Based on the biochemical and physiological attributes of C₄ grasses, and on the close association between decarboxylation pathways and the taxa in which they evolved, the hypotheses tested were: (1) that C₄ grasses would become progressively more abundant as precipitation decreased, with grasses of the NADP-me subtype more abundant in wetter sites and those of the NAD-me subtype more common in arid regions; and (2) that the distribution of grass subfamilies would also be correlated with annual precipitation. The study was conducted along a precipitation gradient in central Argentina, from the eastern Pampas (>1000 mm year⁻¹) to the western deserts and semi-deserts near the Andes (