Changes of photosynthetic capacity of some plant species under very high CO_2 concentrations in Biosphere 2

Conclusions The initial slope of A/ light curve became steep under high CO2 (700 μmol · mol-1) compared with that under low CO2 (350 μmol · mol-1) for the C3 species growing in very high CO2(>2 200 μmol · mol-1) for a long period. The light compensation points remained unchanged, but the light saturation points were found increased. The m,app and Amax of the C3 species increased respectively by 79 % and 80 %, while those of C4 species decreased by 10% and 14%, respectively. The shape of A/light curve of C4 species did not change. Such results indicated that C3 species increased the capacity of photosynthesis, while C4 did not change, otherwise it decreased a little. This work only compared the changes of capacity in photosynthesis of some species under different CO2 levels in Biosphere 2. We need further investigation on the effects of high CO2 on the same species outside Biosphere 2, in order to fully undertand the effects and mechanism of response of plants to the elevated CO2.