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. Data is mean ± SE (n=12). Different
letters in the same CO2 treatment indicate significant
difference among growth stages (p <0.05).