| Based on the data collected from the super-hybrid rice "Liangyoupeijiu" ( Pei'ai64S/9311) and its female parent Pei'ai64S and its male parent Indica rice 9311, their chlorophyll fluorescence parameters and the key indexes of active oxygen metabolism were measured separately under both natural and photooxidized condition. Meanwhile, the distribution of 14CO2 assimilate products and €4 pathway enzymes were studied as well. The results are stated as follows.Under high temperature of strong light, the decrease of PS II primary photochemical efficiency(Fv/Fm)and photochemical quenching coefficient (qP) were low; and the increment of non-photochemical quenching coefficient (qN) were not evident either. While in the natural condition, light energy absorbed by "Licingyoupeijiu" was mostly converted into chemical energy and little was dissipated in the form of thermal energy, which shows its capability of tolerance for photoinhibition. In the comparison of the filial and its parents, it was observed that the young one has, surpassing its male parent, adopted its female parent's features of tolerance for photoinhibition .After the process of photooxidization, both the decrement of the contents of chlorophyll and protein and PS II primary photochemical efficiency (Fv/Fm) as well as photochemical quenching coefficient (qP) and the increment of non-photochemical quenching coefficient (qN) in super-hybrid rice "Liangyoupeijiu" were very small, compared with its parents. These suggest that most light energy absorbed by "Liangyoupeijiu" was converted into chemical energy and little was dissipated in the form of thermal energy. Furthermore, the it had a positive inductive activation of scavenging active oxygen enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), which in turn helped to clear up endogenous active oxygen could be scavenged efficiently and thus limited the membrane-lipid peroxidation. As a result, it was demonstrated that "Liangyoupeijiu" had outgrown its parents in photosynthetic physiology and possessed the advantage of tolerance for photooxidation .In its leaf aging process, the decrement of its contents of chlorophyll and protein and PS II light energy (Fv/Fm, qP and PS II ) were relatively small, while the increment of non-photochemical quenching coefficient (qN) were not obvious either. That again suggeststhe fact that most light energy absorbed by "Liangyoupeijiu" was converted into chemical energy and little was dissipated in the form of thermal energy. Besides, for its inductive activity of scavenging active oxygen enzymes such as superoxide dismutase (SOD) and peroxidase (POD) were high, it had a strong tolerance for photoinhibition and early aging. With the comparison of its parents, it had the characteristics of resistant to early aging in its late process of reproduction, which seemed to have adopted from its female parent other than form its male one.14C was applied studied on the distribution and transportation of photosynthesis assimilate products in "Liangyoupeijhr and it was found out that they were mainly distributed in its panicle other than any other parts, which meant it had a better coordination of source-sink. Measured separately at the early, late and between stages of its milk time, the distribution percentage labeled at upper and lower parts of panicle showed that "Liangyoitpeijiu" had far more potential strong grains in the upper than its male parent 9311 and that it had a longer milk time. This is perhaps one of the possible reasons for its super high yielding.Last but not least, stronger activations of key enzymes, fixed by CO2 , in €4 pathway, such as PEPcase, NADP-ME, NAD-ME and PPDK, were demonstrated in "Liangyoupeijiu". This was speculated as one of its physiological reasons for its tolerant for photoinhibition.As a conclusion, the high yielding of "Liangyoiipeijiu" owed a lot to its tolerance for photoinhibition/photooxidation, its resistance to early aging and its capacity of well-coordination of source-sink as well as its activation of €4 pat...
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