Polyploidy-mediated divergent light-harvesting and photoprotection strategies under temperature stress in a Mediterranean carnation complex

Polyploidy can induce physiological novelties with adaptive potential, which may influence the range of environmental conditions that a neopolyploid tolerates. Dianthus broteri (Caryophyllaceae) is an autopolyploid complex that comprises four ploidy levels (2 x, 4 x, 6 x and 12 x) with separate distributions in the Iberian Peninsula, occupying different ecological niches along a gradient of temperature and aridity. We designed an experimental approach to disentangle the differential photochemical responses to temperature (from -3 degrees C to 53 degrees C) among D. broteri cytotypes by the measurement of leaf chlorophyll fluorescence. Our results showed higher energy fluxes, F-v/F-m and delayed fluorescence values along low and mild temperature levels in lower ploidies (2 x and 4 x) compared to higher ones (6 x and 12 x). This pattern would allow lower cytotypes to enhance their photosynthetic apparatus functionality in environmentally non-stressful habitats as those they inhabit. Contrarily, the 6 x cytotype exhibited the overall lowest energy fluxes based on a reduced absorption while maximizing its flux ratios. Moreover, the 12 x cytotype had notably high dissipation fluxes to ensure photoprotection, maintaining low but constant photochemical efficiency. These latter strategies would cause the reduction of photosynthetic capacities but help higher ploidies to tolerate the semi-arid Mediterranean environmental conditions with high temperatures under which they live.