CK, SI and CI stand for ambient [CO2], stepwise increase of [CO2] by ~40 μmol mol-1 in each season, and constant increase of [CO2] by ~200 μmol mol-1 for all seasons, respectively.T mean, T max andT min are daily mean air temperature, daily maximum air temperature and daily minimum air temperature. Data is mean±SD.
Table 2 Effects of different treatments of [CO2] elevation, observation time, and their interactions on Fv/Fm(maximum photochemical efficiency of PSII), ψo(the probability that trapped exciton moves an electron further than QA­), φEo (electron transport quantum yield) and PIABS (performance index) during different growth stages.