Effect of stomatal morphology on leaf photosynthetic induction under fluctuating light across diploid and tetraploid rice

Polyploid plants are widely used in crop breeding for their superior performance in anatomical size and nutrient content. Photosynthesis is often affected by highly variable light conditions in the field. So far, few studies have been focused on the comparison of photosynthetic induction between tetraploid and diploid rice. Here, we for the first time compared the leaf photosynthetic induction and the underlying mechanism between tetraploid and diploid rice. After polyploidization, the plants displayed a larger size and lower density of stomata, which resulted in slower stomatal opening in response to a stepwise increase in light intensity. Further analysis indicated that stomatal opening, instead of biochemical processes, is the most important factor that contributes to the difference in photosynthetic induction between tetraploid and diploid rice. With lower stomatal conductance (gs), tetraploid rice displayed a lower intercellular CO2 concentration (Ci), and therefore lower photosynthetic efficiency during light induction. However, we observed a higher intrinsic water use efficiency (WUEi) in tetraploid rice than in diploid rice, which may contribute to the survival and growth of plants under water-limiting conditions. This study highlights the function of stomata in regulating photosynthetic induction and water use efficiency under fluctuating light, which will help the improvement of crop photosynthetic efficiency in the future.