| Bayberry(Myrica rubra Sieb. et Zucc.) is the native subtropical evergreen economic tree species in China whose cultivated areas account for more than 99% of the world wide are from China, among which, Zhejiang province is the main productive area.This study found that under natural conditions, especially in winter and early spring, low temperature, light often occur simultaneously as the compound stress, which will not only leads to the serious photo inhibition, but also induce the irreversible damage of photosynthetic apparatus,will become a serious damage to the evergreen fruit tree---bayberry. Along with the increase of market demand, it is important to ensure the fruit quality need to be guaranteed. As photosynthesis is the basic condition for high-quality fruit,deep analysis on the photosynthetic mechanism of bayberry need further research.The paper intended to provide theoretical basis for the research the development of cultivation technique on alleviating the harms to bayberry, utilized the full-length cDNA sequence of separated bayberry PsbA gene and FtsH gene, taked ‘Dongkui’and ‘Tanmei’ as test materials for their different tolerances for low temperature, light and combined stress, studyed PsbA and FtsH genes expression patterns under the stress of low sowing with gas exchange and chlorophyll fluorescence measurement technology which combined with molecular biology methods, analyzed the regulation mechanism of PsbA and FtsH genes under stress conditions. The main results are listed as below:1.The Pn, AQY and CE of bayberry leaf were significantly lower, whose reduced amplitude increased with the increasing of the degree of low temperature stress and time, while the photosynthesis recovery degree after chilling stress appeared opposite result.,under low temperature stress. Shading could reduce the low temperature stress,however.The Pn, AQY and CE of ‘Tanmei’ leaf decreased significantly less than the ‘Dongkui’ under the same condition of low temperature and light stress, showed that ‘Tanmei’ may better than ‘Dongkui’ in terms of the resistance of low temperature, light stress.2.The ΦPSII and ETR of bayberry rised first and then went down,and the ΦPSII, ETR ‘Tanmei’was greater than the ‘DongKui’ in winter sunny days; In cloudy days, the changes of ΦPSII and ETR were much smaller, which rised slightly at 13;00 and the ΦPSII, ETR of ‘Tanmei’ was greater than the ‘Dongkui’.This suggested that the resistance of low temperature, light stress of ‘Tanmei’ was superior to the ‘Dongkui’.3. The chlorophyll fluorescence imaging analysis showed that in the winter cold weather, the leaves of ‘Dongkui’ and ‘Tanmei’ had the same changing trend in one day, appearing the trend of rised smoothly and then decreased in winter.The maximum value arrived before and after 12:00,while the value of ETR、qP、ΦPSII of ‘Tanmei’ were higher than ‘Dongkui’,and the non photochemical quenching(qN) was initially falling after rising.4. Under low temperature stress, the ‘Dongkui’ PsbA gene and FtsH gene expression levels all decreased, while the ‘Tanmei’ PsbA gene expression decreased, FtsH gene expression did not change significantly, whose reduction degree along with the degree of temperature stress and time increases, however, the increased amount of gene expression were higher after recovery processing; Shade treatment could reduce the extent of the damage the plant.The PsbA gene and FtsH gene expression changes of ‘Tanmei’ were less than ‘Dongkui’ under same condition of low temperature and light stress,indicated that ‘Dongkui’ was more resistant to low emperature and light stress and had better adaptability than ‘Tanmei’. |
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