AI+200 and AI+160 were short-term (one growing season) abrupt increase of [CO2] by ~200 μmol mol-1 and ~160 μmol mol-1, respectively. CI: constant increase of [CO2] by ~200 μmol mol-1 based on ambient [CO2] for four generations. SI: stepwise increase of [CO2] for four generations with the [CO2] being ~40, 80, 120 and 160 μmol mol-1 higher than ambient in each generation. Significance levels are indicated by *, ** and *** for p <0.05, p <0.01 andp <0.001.
Table 5 Predawn values of Fv/Fm (maximum photochemical efficiency of PS II), ψo (probability that trapped exciton moves an electron further than QA-), φEo (electron transport quantum yield) and PIABS (performance index) and results of analysis of variance among growth stages under different treatment of CO2 concentration [CO2] elevation.