The long and winding road to Kranz anatomy

PROCHETTO SANTIAGO;; REINHEIMER RENATA

Congreso; Monocots VI; 2018

Kranz syndrome is a specific set of leaf functional properties in plants using C4 photosynthesis. Such syndrome includes the existence of distinct compartments in the leaves: 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 distinct C3, C4 and intermediates grasses to comparatively study anatomical changes that characterize each type of leaf. We determined that the grade of differentiation in photosynthetic structures increases towards the distal extreme of all leaf types analysed. We observed qualitative and quantitative differences among species in vascular bundles density, chloroplasts distribution and bundle sheath size. Altogether, this analysis allows us to increase knowledge on the long and winding road that lead to the Kranz anatomy in grasses. Key words: bundle-sheath, C4 photosynthesis, grasses, evolution, leaf.