Photosynthesis And Photoinhibitipn Of Two Superhigh-yield Rice Hybrids, Liangyoupeijiu And Hua-an3

Photosynthetic characters were compared between two newly developed superhigh-yield rice hybrids, Liangyoupeijiu (Pei-ai64S X 93-11) and Hua'anS (X07S X Zihui100), and the traditional rice variety Shanyou63 (Zhenshan97A X Minghui63), which has been popularized large area in China for many years. The results showed:1. The net photosynthetic rates (Pn) of the two superhigh-yield rice hybrids were higher than that of Shanyou63 from seedling stage to heading stage, especially under midday strong sunlight at seedling stage and under twilight at tillering and heading stage. The results suggested that the two superhigh-yield rice hybrids not only had higher Pn and higher resistance to midday photoinhibition, but also had the abilities to use dim light at morn and dusk efficiently for photosynthesis.2. The higher pigments content and Cha/b ratio of flag leaves of the superhigh-yield rice hybrids allowed them to use the solar energy more efficiently, and the superhigh-yield rice hybrids had higher water use efficiency than Shanyou63 at heading stage, which made them use water more economically.3. The 77K fluorescence emission of the thylakoid membrane of Liangyoupeijiu and Hua-an3 were higher than that of Shanyou63 at all developmental stages. The Gaussan analysis of the emission spectra showed that the fluorescence emission of LHCs and RCs of the two superhigh-yield rice hybrids were stronger than that of Shanyou63, which indicated that Liangyoupeijiu and Hua-an3 had higher abilities to absorb and transfer light energy than Shanyou63 had.4. Higher Pn of the two superhigh-yield rice hybrids at seedling and tillering stage could help them establish bigger colonies, which could benefit them a lot during the later developmental stages.5. Most of the out-put of crops root from the photosynthesis of flag leaves. At heading stage, the flag leaves of the two superhigh-yield rice hybrids had a littlehigher Pn than Shanyou63, but a much higher AQY and CE, i.e., the two superhigh-yield rice hybrids, Liangyoupeijiu and Hua-an3 could use light energy and CO2 much more efficiently than Shanyou63. And we for the first time bring forward the theory that the higher ability to use light energy and CO2 is the key reason for the higher yield of Liangyoupeijiu and Hua-an3.Photinhibition and photoprotection abilities were further compared between the twosuperhigh-yield rice hybrids and Shanyou63, the result showed:1. The photoprotection mechanisms of Liangyoupeijiu and Hua-an3 worked more efficiently than those of Shanyou63, and the photosynthetic functions of them could be restored more rapidly after photoinhibition. Higher abilities of photoprotection and faster restoration after photoinhibition might be one of the important reasons for the higher yield of the two superhigh-yield rice hybrids.2. The de-epoxidational xanthophyll pigments, A and Z, of Liangyoupeijiu and Hua-an3 could be accumulated more rapidly under photoinhibition and then restored more rapidly after the photoinhibion than that of Shanyou63. During the photoinhibition, the DES of the xanthophylls cycle arrived its maximum at about 30min, while the retrain of photosynthesis getting more seriously, we postulated that the role of xanthophyll cycle in photoprotection was that the fast accumulation of Z triggered the photoprotection mechanisms.3. Shanyou63 was more violable to midday photoinhibition than the two superhigh-yield rice hybrids.4. When subjected to midday strong sunlight, Z and A of the rice hybrids accumulated rapidly while the xanthophyll pool kept unchanged, this suggested that it was the fast accumulation of de-epoxidational xanthophyll pigments Z and A, not the xanthophyll pool that played the important role in protecting photosynthetic organisms from excessive light.5. Of all the three rice varieties studied, no linear correlativity was observed between DES and NPQ during photoinhibion, so we further postulated that cyclic elec...