FIGURE 1.

Effects of elevated CO₂ and heat stress either alone or combined on the CO₂ assimilation capacity in tomato leaves. (A) the net photosynthetic rate (P_n); (B) the maximum carboxylation rate of RuBisCO (V_cmax), (C) the maximum rate of RuBP regeneration (J_max). At the four-leaf stage, tomato seedlings were exposed to either ambient (380 μmol mol^-1) or elevated CO₂ concentration (800 μmol mol^-1). After an acclimation period of 48 h, half of the seedlings from both CO₂ conditions was challenged with a 24 h heat stress (42°C temperature) and then allowed to recover for 24 h. Measurements were taken on the third fully expanded leaves using an open-flow infrared gas analyzer adapted with light and temperature control systems (Li-COR 6400, Li-COR, Lincoln, NE, United States). The results are expressed as the mean values ± SD, n = 6. Different letters above the bars indicate significant differences at P < 0.05 according to Tukey’s test.