| Sweet cherry as the popular pollution-free fruit has a good market prospects in China. However,due to the climatic conditions of high temperature and strong light in summer in South China, the large werea cultivation of sweet cherry was restricted objectively.In this experiment five sweet cherry varieties ( Brooks, Lapins, Summit, Hongdeng, Hongmi)which grafted on the DQY’, Gisela 5 and Gisela 6 rootstocks were as studied objects to analyze the the relationship between photosynthesis of sweet cherry leaves and external factors (shading, light,temperature, etc.) and internal factors (rootstock varieties and sweet cherry varieties) .And all varieties except Summit were studied and analyzed the photosynthetic and fluorescence parameters growing under three shading conditions. And the physiological indexes such as plant height, crown width, main branch length and main branch thickness were measured for the above five varieties grafted on Gisela 6 rootstocks. The chlorophyll fluorescence characteristics of Brooks, Lapins and Summit grafted on Gisela 6 rootstocks were measured under different temperature and different light intensity, and the light response curve was simulated. The main conclusions were as follows:1 The Summit on the Gisela 6 rootstock had better overall physiological characteristics than Brooks and LapinsOn the Gisela 6 rootstock, Summit’s height was the smallest, the main branch was the thickest,the fruit weight was the largest, the peel was red, the fruit was heart shape, the fruit shape index was higher; the height and the crown width of the Lapins were the largest, the main branch was long and thick, the peel was purple, fruit shape was oval, the fruit was relatively hard , fruit shape index was higher; height of Hongdeng was larger, crown width was smaller, the smallest DBH, the main branch was shorter and thinner, larger single fruit weight, fruit was pink, kidney shape, the hardness was the smallest; The crown of Hongmi was larger, the DBH was the largest, the main branch was the longest and the most thin, single fruit weight was minimal, peel was yellow mixed with red, fruit was heart shape, the soluble solids content of fruit was the highest; crown width of Brooks was the smallest ,the fruit was heavier, peel was dark red, the shape of the fruit was oblate, the hardness wasthe largest,soluble solids content was higher.2 Shading in summer could improve the photosynthesis of sweet cherry, and there was a great difference among different combinationsThe Fv / Fm and Pn of sweet cherry leaves exposed to long-term natural light in summer were decreasing, while shading treatment could alleviate the decline of Fv / Fm and Pn. The photosynthetic organs of sweet cherry leaves exposed to strong light were continuously destroyed and the photosynthetic activity decreased, that was, the non - stomatal limitation caused the decrease of photosynthetic rate. The effective photosynthetic radiation of single layer net shading treatment was reduced by 55%, which could significantly improve the Pn and LUE of sweet cherry leaves. The effective photosynthetic radiation of two layer net shading treatment was reduced by 85%, but the LUE was significantly increased. Strong light had a greater effect on the varieties grafted on ’DQY’rootstock, but the single layer net shading treatment was very significant to the improvement of Pn.While the sweet cherries on the Gisela 5 and Gisela 6 rootstocks were less affected by the summer strong light. The effect of shading on the Pn of Gisela 5 and Gisela 6 rootstocks was less than that of’DQY’. In addition, the Pn value, LUE and Fv / Fm of Brooks were higher under low light, which showed good adaptability to low light. Lapins showed good adaptability under strong natural light.3 The optimal growth temperature of Brooks, Lapins and Summit was 25-30 ℃, Lapins had better strong light adaptability than Summit and BrooksTemperature and light intensity had an important role in growth of sweet cherry and the development of fruit. Simulation of natural light with light of dysprosium lamp,In five dysprosium light intensity under different temperatures to deal with sweet cherries, we found that the Fv / Fm values of Brooks, Lapins, Summit which grafted on Gisela 6 rootstock at 25-30 0C ambient temperature were significantly higher than those of other environmental temperatures. The Fv / Fm values of Brooks were not significantly different at 25 ℃, 30 ℃, and 35 ℃, and Brooks had a relatively large suitable temperature range. When controlling room temperature at 30 ℃ and giving different brightness to sweet cherries (control the number of dysprosium lamps to simulate different light intensity), we found that the Fv / Fm of Brooks, Summit under the treatment of five dysprosium lamps was significantly higher than that of other light intensity treatments, while Lapins treated by seven dysprosium lamps was significantly higher than other light intensity treatment. This results indicated that Lapins needed stronger light intensity than Brooks and Summit in order to obtain the best photosynthesis.4 Summit had the greatest ability to use low light and the highest photosynthetic potential, Brooks had strong ability to accumulate organic matter in low light conditions, and was more shade-enduring,Lapins had the strongest ability to use glareThe consumption of photosynthetic products from Summit was high. Summit’s LUE was greater,the ability to use low light was stronger, the response to light was more sensitive, Summit adapted to a wide range of hight intensity, and being more shade-enduring. Summit had the highest photosynthetic potential. Lapins> Summit> Brooks was the order of LCPs for the three species. Brooks required the least amount of light to accumulate organic matter. In terms of LCP,Lapins’ LCP was larger than the other two cultivars, and Lapins’ ability to accumulate organic matter in low light conditions is not as good as the other two varieties. Lapins had strong ability to use strong light, and the use of low light range was relatively larger. Brooks had lower breathe consumption, which was beneficial to photosynthate accumulation. In term of AQY, Summit had the strongest and Brooks were the smallest,which indicated that the low light utilization ability of Summit was higher, and LCP of Lapins were the largest in the three varieties, which indicated that Summit had the strongest weak light utilization ability, and Brooks had strong ability to accumulate organic matter in low light conditions, and was more shade-enduring. |
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