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. Values are probability levels for significant differences.

Table 3 Relative change in maximum photochemical efficiency of PS II (F_v/F_m) between predawn and other observation time points under different treatment of elevated CO₂ concentration [CO₂].