Study On Photosynthetic Characteristic Of Maize C₄ Type Pepc Gene In Transgenic Wheat

T₁,T₂ generation of wheat plants with transgenic maize C₄-type pepc and receptor (Zhoumai19) as experimental materials, PEPCase (phosphoenolpyruvate carboxylase) activity of transgenic wheat functional flag leaf was determined ,also response curve of transgenic high efficiency wheat's photosynthetic rate to light intensity, temperature and CO₂ concentration was researched and established. We also analyzed daily changes of photosynthetic rate in field and the high temperature and strong light stress response characteristics of the transgenic wheat. Besides, we compared portions of the transgenic T₁ generation of wheat with control of per ear weight and 1000-grain weight. The findings are as follows:1. For transgenic T₁ generation of wheat yield, relative activity of PEPCase of 10 strains and photosynthetic rate of 58 strains were determined. Compared with control, transgenic T₁ generation increased by 120%,26% respectively, reaching to 0.048,31.2μmolCO₂·m^-2·s^-1. For transgenic T₂ generation of wheat yield, relative activity of PEPCase of 30 strains and photosynthetic rate of 65 strains increased by 163%,24% respectively, reaching to 0.158,30.1μmolCO₂·m^-2·s^-1. PEPCase activity and net photosynthetic rate was extremely significantly positive correlation(r=0.6944**).2. Under low light intensity, there is no obvious difference between transgenic plants and the control in photosynthetic rate and apparent quantum efficiency. The result shows that the ability of transgenic wheat to use weak light is equal to that of control. As light intensity increased, the transgenic wheat showed stronger ability to use light, and its light saturation point is about 1680μmol·m^-2·s^-1, 20% higher than the control. Light-saturated photosynthetic rate increases by 29%.3. Photosynthetic rate of transgenic wheat is generally higher than the control at 15-40℃. Transgenic plants have a strong ability to agree with high temperature. The optimum temperature for photosynthesis of transgenic plants is about 30℃, while the control is about 25℃.4. The carboxylation efficiency of transgenic wheat was increased by 23% comparing with the control. CO₂ compensation point drops to 75.4μmol·mol^-1, 2% lower than the control, showing that the transgenic wheat's ability to use CO₂ is enhanced.5. The daily changes of photosynthetic rate in the heading period of the wheat in the control showed double-peak curves, with"lunch break"phenomenon found, while that of the transgenic wheat tended to show a single one; In most of the time, the photosynthetic rate of the transgenic wheat is higher than that of the check and the difference in between is significantly greater in 9:00-14:00 the strong light period.6. When treated by 7th after flowering of high temperature (about 34.8℃) and strong light (about 1900μmol·m^-2·s^-1) 3h, photosynthetic rate at favorable environment of transgenic wheat was decreased by 11%,to 25μmolCO₂·m^-2·s^-1,while the control decreased by 32%,to 15.9μmolCO₂·m^-2·s^-1. Chlorophyll fluorescence parameters Fv/Fm was respectively decreased by 9%,19% . Fv '/ Fm',ФPSII, qP was decreased in varying degrees and the decrease of transgenic wheat was lower than the control. NPQ was significant increased, and transgenic wheat has a bigger rise comparing with the control. When treated by 14th after flowering,the trend of photosynthetic rate,Fv/Fm,Fv'/Fm',ФPSII,qP,NPQ was similar to that of 7th after flowering. The result showed that transgenic wheat has good capacity of heat dissipation and characteristics of light inhibition.7. All per ear weight of portion of transgenic T₁ generation wheat which was determined were heavier than that of the control(up to 1.5g), and they were 1.72g,2.12g,1.69g,2.27g,2.15g,1.73g, maximum increased 51%. Most 1000-grain weight was also heavier than that of the control(up to 43.3g), and they were 45.1g,46.7g,43.6g,48.5g,46.7g,40.6g,maximum increased 12%. It showed that transgenic wheat has the potential to increase grain yield.