DEVELOPMENTAL CHANGES IN LEAF ANATOMY BRINGS NEW INSIGHTS IN GRASS PHOTOSYNTHESIS EVOLUTION

REINHEIMER RENATA; PROCHETTO SANTIAGO;

Congreso; LIV Reunión anual de la sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2018

Kranz syndrome is a specific suite of leaf functional properties in plants using C4 photosynthesis. These include the existence of discrete compartments: one more closely connected to the atmosphere, where the CO2 is captured; and a larger one, where the Calvin cycle takes place.The current model of C4 photosynthesis evolution from a C3 ancestor proposes a series of gradual leaf anatomical changes followed by biochemical adaptation of the enzymatic machinery. This transition, which occurred several times in a wide range of angiosperms lineages, is particularly interesting in grasses. In this work, we performed qualitative and quantitative measures in leaf cross sections of close related C3, C4 and intermediates grass species to comparatively study anatomical changes that characterized each type of leaf. We also combine this information with leaf physiology measurements (gas exchange assays and chlorophyll fluorescence) to correctly interpret leaf anatomy.We determine that the grade of differentiation in photosynthetic structures increases towards the distal extreme of all type of leaves analysed. Likewise, we observed qualitative and quantitative differences between species in vascular bundle density, chloroplast distribution and bundle-sheath size. Altogether, this analysis allows us to increased knowledge on the evolutionary path that lead to Kranz anatomy in grasses.