Photosynthesis optimized across land plant's phylogeny

Abstract

[eng] A new emerging pool of gas-exchange data from mosses to angiosperms is widening our knowledge about photosynthesis across the land plant groups. More basal groups achieve lower photosynthetic benefits per leaf mass area (LMA) and/or N content compared with angiosperms, likely due to a differential resource investment that could indicate some trade-offs between maximizing photosynthesis and stress tolerance strategies. Photosynthetic capacity increases along the phylogenetic continuum, reaching its maximum in angiosperms, based on a balanced colimitation among its diffusional and biochemical determinants, which questions the possibility of improving crop maximum photosynthetic capacity beyond its current limits. Until recently, few data were available on photosynthesis and its underlying mechanistically limiting factors in plants, other than crops and model species. Currently, a new large pool of data from extant representatives of basal terrestrial plant groups is emerging, allowing exploration of how photosynthetic capacity (Amax) increases from minimum values in bryophytes to maximum in tracheophytes, which is associated to an optimization of the balance between its limiting factors. From predominant mesophyll conductance limitation (lm) in bryophytes and lycophytes (fern allies) to stomatal conductance (ls) and lm colimitation in pteridophytes (ferns) and gymnosperms, a balanced colimitation by the three limitations is finally reached in angiosperms. We discuss the implications of this new knowledge for future biotechnological attempts to improve crop photosynthesis.