LAUSR

The studies investigating the mechanisms underlying the variation of photosynthesis along plant phylogeny and, especially, during domestication are of great importance, which may provide new insights to further improve crop photosynthesis. In the present study, we have compiled a database including 542 sets of data of leaf gas exchange parameters, leaf structural and chemical traits in ferns and fern allies, gymnosperms, non-crop angiosperms and crops. We found that photosynthesis was dramatically improved from ferns and fern allies to non-crop angiosperms, and it further increases to crops. The improvement of photosynthesis during phylogeny and domestication was related to the increments of CO2 diffusional capacities and, to a less extent, to biochemical capacity. Cell wall thickness rather than chloroplast surface area facing intercellular air spaces drives the variation of mesophyll conductance. The variation of maximum carboxylation rate was not related to leaf nitrogen content. The slope of the relationship between mass-based photosynthesis and nitrogen was lower in crops than that in non-crop angiosperms. This study suggested that the manipulation of cell wall thickness is the most promising approach to further improve crop photosynthesis, and that an increase of leaf nitrogen is less efficient to improve photosynthesis in crops than in non-crop angiosperms.