Study On Photosynthetic Characteristics Of Peach Based On Heterosis Of Assimilation Capacity

The photosynthetic heredity research is a new method of evaluating heterosis that depends on photosynthetic traits of crops, and also is a new field of genetic and breeding research. Photosynthesis is the essence of plant production; it is the base of biosphere obtaining material and energy. The higher photosynthetic ability and longer functional period of the hybrid are important to improve yield. Recently, the previous research of offspring photosynthetic performance mostly focused on field crops, forest species, ornamental and medicinal plants, in the category of horticultural crops mainly focused on gramineous plant sugar cane and vegetable crops, seldom in woody fruit trees. This research selected the current widely cultivated six peach species and their eight cross combination progenies (F1) as the trail materials, studied their summer and autumn photosynthetic performance related indexes (photosynthetic and chlorophyll fluorescence characteristics) and the heterosis changement, and then analyzed the affecting factors, meanwhile researched the diurnal of photosynthetic characteristics with one group of those materials. The results showed that:1. The chlorophyll content(Chl.) had a high significant positive correlation with the carotenoid content (Car.), CO2 saturated net photosynthetic rat (CSPn) had a significant positive correlation with carboxylation efficiency (CE) but light saturated net photosynthetic rat (LSPn) had a negative relationship with CE. All of minimal fluorescence (Fo), maximal fluorescence (Fm) and non-photochemical fluorescence quenchin (NPQ) had significant positive correlations. Each of the three indexes had a significant or high significant positive correlation with electron transport rate (ETR) and but it was with PSⅡactual photochemical efficiency (Yield). In addition, photochemical maximum efficiency of PSⅡ(Fv/Fm) relatively stable. According to the results from clustering analysis,8 hybrids were classified into three groups. Yumyeoung×Xiacui, Yumyeoung×Hujingmilu were excellent in photosynthesis performance; Yumyeoung×Xiahui 5#, Mika×Xiacui, Mika×Hujingmilu and Mika×Xiahui 5# were general in photosynthesis performance; Diaozhibai×Xiacui and Diaozhibai×Xiahui 5# were relatively worse in photosynthesis performance.2. Light compensation point (LCP), PSⅡactual photochemical efficiency (Yield), minimal fluorescence (Fo) in July and chlorophyll content(Chl.), carotenoid content (Car.), water use efficiency (WUE), CO2 compensation point (CCP), Yield in September of the hybrid showed positive heterosis. Stability of photosynthetic and chlorophyll fluorescence characteristics of the hybrid were great influenced by their parents.3. Diurnal variation of net photosynthetic rate (Pn) of 8 crossbreed peach and their parents were determined in the middle of July and the last third of September. The sequence of environment factors that affected heterosis of Pn were found out with grey system theory applied, and the correlation between heterosis of Pn and chlorophyll content were also analyzed. The results showed that CO2 concentration was the main factor that affected heterosis of Pn. Not only the peak of Pn in a day but also diurnal integral value of Pnhad a negative relationship with Chl.(a+b), Chl.a and Chl.b in the middle of July but had a negative correlation with carotenoid content in the last third of September. Meanwhile, mid-parent heterosis and transgressive heterosis of the peak of Pn in a day and diurnal integral value of Pn had a negative correlation with Chl.(a+b), Chl.a and Chl.b in the two periods.4. Net photosynthetic rate (Pn) of F1 hybrids of Diaozhibai×Xiacui showed positive heterosis at noon, transpiration rate (Tr) and stomatal conductance (Gs) took on negative heterosis while the heterosis of water use efficiency (WUE) was opposite all day long in autumn. Positive correlations were all observed by correlation analysis between Pn and Gs as well as Tr and Gs. Grey correlation analysis indicated that atmospheric CO2 concentration (Ca) was the main factor which affected heterosis rate of Pn, Tr and Gs.