Figure 7.

Differential reduction in photosynthesis of wild-type and NDH-inactivated plants grown in low air humidity. Photosynthesis and evapotranspiration of 5-week-old wild-type and ndhB⁻ plants are shown in normal (60 relative %) and low (30 relative %) air humidity on the day preceding and following the humidity transition, respectively. The whole-plant photosynthesis and evapotranspiration values recorded in one experiment were the sum of four to eight plants of the same type grown in one computer-controlled growth chamber recording CO₂ consumption and water vapor condensation. On the left net photosynthesis calculated for one plant is displayed as the mean ± sd of four independent experiments. On the right evapotranspiration calculated for one plant is displayed as the mean ± sd of four independent experiments. Asterisk indicates significant differences from controls (P < 0.05). Low air humidity generated a difference in photosynthesis of ndhB⁻ and wild-type plants, demonstrating an enhanced sensitivity of the ndhB⁻ transformants to humidity stress. Evapotranspiration of ndhB⁻ and wild-type plants showed a similar response, indicating that their stomata responded non-differentially to low air humidity.