Variation in photosynthetic induction between super hybrid rice and inbred super rice

It is well documented that yield superiority of super hybrid rice is linked with its improved photosynthetic capacity and/or efficiency. In natural environments, the amounts of CO₂ assimilated by plants was also impacted by the rapidity of leaf photosynthesis response to fluctuations of light. However, it remains unknow whether the high yield of super hybrid rice was associated with photosynthetic traits under dynamic state. Here, photosynthetic traits under steady-and dynamic state in two super hybrid rice varieties (Ylinagyou 3218 and Yliangyou 5867) with high yield and two inbred super rice varieties (Zhendao 11 and Nanjing 9108) with lower yield. Under steady state, the net photosynthetic rate (A*) in super hybrid rice was 25.3% larger compared with inbred super rice. During photosynthetic induction, there was no obvious association of the rapidity of net photosynthesis rate (A) to sunflecks with rice subpopulations. Stomatal conductance (g_s) of super hybrid rice increased slower than that of inbred super rice. The cumulative CO₂ fixation (CCF) during photosynthetic induction was 25.2% larger in super hybrid rice than that in inbred super rice. The primary limitation during induction was biochemical limitation rather than stomatal limitation. There was a significantly positive relationship between A* and CCF, while A* was not related with the induction response rate of A. Overall, A* and CCF in super hybrid rice have been improved together, which contributed to its yield superiority, whereas its yield potential still can be improved by increasing induction rate of A under fluctuations of irradiance.