Increased Photosynthetic Capacity as a Mechanism of Drought Adaptation in C3 Plants

Premise of research. Plant available soil moisture can influence the evolution of C3 photosynthesis in multiple ways. Water limitation could select for enhanced photosynthetic capacity in order to overcome stomatal limitations to CO2 supply. Alternatively, moisture-limited soils may select for reduced photosynthetic capacity because of the high costs of investment in N-rich Rubisco under chronic CO2 limitation.Methodology. Using literature data on photosynthetic capacity, phylogenetic information, and georeferenced climate records, we assessed the magnitude and direction of the relationship between photosynthetic capacity, as described by the carboxylation capacity of Rubisco (Vcmax) and annual precipitation (MAP). We also examined the association between leaf nitrogen content expressed on leaf area and leaf mass bases (Nmass and Narea, respectively) and MAP.Pivotal results. Both Vcmax and Nmass increased with decreasing MAP, a finding that was relatively consistent across growth forms, including deciduous and evergreen angiosperms. There was no association between Narea and MAP.Conclusions. Selection by dry environments may be responsible for the evolution of increased photosynthetic capacity and leaf N content in C3 plants despite potential metabolic costs of maintaining high investment in N-rich Rubisco. Greater photosynthetic capacity can maximize photosynthetic carbon gain per unit water transpired, making it an important adaptation to arid/semiarid environments.