Turn C < Sub > 4 < / Sub > Gene (pepc&ppdk) Rice Photosynthetic Physiology And Light Suppression Characteristics Research

This paper chose PEPC&PPDK transgenic rice(R2P) and its wild style (WT) R299to study the photosynthetic characteristics at booting stage as well as compare the changes of chlorophyll fluorescence parameters under photooxidation conditions.Main achievements were as follows:1. To elucidate the mechanism of photoprotection in PEPC&PPDK transgenic rice during the booting stage. To compare the diurnal variation in net photosynthetic rate (Pn),PS II primarily chemical efficiency(Fv/Fm)。chlorophyll fluorescence parameters Fo and PI(abs),endogenous superoxide anion generation rate (O2-), the malondialdehyde (MDA) content, the activities in protective enzymes between PEPC&PPDK transgenic rice and WT. Results showed that with the change of temperature and light intensity in test day, the Fv/Fm,PI(abs) and Pn were decreased at the beginning and then increased, the chlorophyll fluorescence parameters Fo, the activities of various protective enzymes SOD, POD, CAT and the generation of O2-and MDA content increased at the beginning and then decreased both in PEPC&PPDK transgenic rice and WT.Relative to untransformed rice, PEPC&PPDK transgenic rice exhibited higher photooxidation induced activities of SOD,POD,and CAT gradually, which led to a less generation rate of O2-and MDA accumulation. Correspondingly, PEPC&PPDK transgenic rice revealed a higher level of Fv/Fm, and net photosynthetic rate, which showed a stronger tolerance to strong light intensity and temperature. It suggested that the photooxidation tolerance of PEPC&PPDK transgenic rice was related with the higer antioxidant enzymes (SOD,POD,CAT) activities and lower levels of O2-and MDA and stabler PSⅡ activity than WT.2. This study compared the photosynthetic physiological characteristics in the pregnant period in leaves of transgenic rice PEPC&PPDK and its WT.Results showed that in the reproductive growth stage,with the full exhibition of flag leaves,, the generation of O2-and MDA content increased both in PEPC&PPDK transgenic rice and its wild type and a significant correlation was found between them, and the two changes were positively correlated with SOD, POD, CAT, whose activity changing trend were negatively correlated.This showed that the antioxidant enzymes play an important but limited role in response of the chloroplast membrane system injury made by superoxide anion in the early stage of rice senescence, the damage would continue after a period of time.It is speculated that the damage on chloroplast by the superoxide anion and the membrane lipid peroxidation product accumulation would be one of the resaons which result in the decline of photosynthetic rate in the later stage of rice flag leaves full exhibition.Compared with R299, the activities of SOD,POD,and CAT of R2P increases quickly in the early stage of flag leaves full exhibition and later decreased less, superoxide anion generation rate and membrane lipid peroxidation product accumulation was lower than that of R299, It showed transgenic rice R2P has a more efficient system on active oxygen scavenging and more anti-aging than R299.3. Under the conditions of photoinhibition and photooxidation,study the changes of chlorophyll fluorescence parameters and active oxygen metabolism index in ransgenic rice R2P and its R299, The results showed that, under the high temperature and high light intensity conditions, different genotypes rices of R2P and R299both showed the phenomenon of photoinhibition at high temperature and high light intensity conditions., the chlorophyll fluorescence parameters Fo, Fv/Fm of R299changed significantly.Under the conditions of photoinhibition.In the noon,Fv/Fm of R2P decreased less and the increase of Fo was not significantly, which showed a higher efficiency of the conversion of light energy to chemical and a higher photooxidation tolerance.Under the treat of photoinhibition,the chlorophyll content of transgenic rice R2P decreased slightly, showing the characteristics of tolerance for photooxidation.At the same time, the R2P’s Fv/Fm decreased less, photoinhibition and, dissipation of heat but higher efficiency of conversion with light energy and chemical,, which showed a relation of higher photochemical efficiency and high tolerance to photoinhibition, these results provide more evidences for the futher study of the photoinhibition mechanism and high photochemical efficiency of the transgenic rice.