Stomatal Kinetics Posed a Major Limitation to Photosynthetic Induction Under Well Water and Drought Stress Conditions

Drought stress is one of the major factors limiting crop growth and yield formation worldwide. Few studies have investigated the effect of drought stress on leaf photosynthetic processes across diploid and tetraploid rice under fluctuating light. Here, we observed less and larger stomata in tetraploid than diploid rice, which resulted in slower stomatal kinetics and photosynthetic induction in tetraploid rice. Drought stress significantly increased the response rate of stomatal conductance and photosynthesis to fluctuating light. Further analysis indicated that stomatal opening, instead of biochemical processes, was the major factor limiting photosynthetic induction under both well water and drought stress conditions. With less and larger stomata, tetraploid rice showed a higher water use efficiency, which also thereafter contribute to obtain a higher photosynthetic efficiency under drought stress. These results mainly emphasized the important role of stomatal morphology in regulating stomatal kinetics and photosynthetic induction under drought stress, which may contribute to improve photosynthetic efficiency in future climate change conditions.