| Walnut（Juglans regia L）,was a perennial deciduous tree belonging to the genus Juglans.China has a long history of cultivation and has planted plants in Xinjiang,Yunnan and Gansu.Among them,Longnan,as the main producing area of walnuts in Gansu Province,has a distinct vertical climate,a mild and humid climate,and a long rainy season.Occasionally,‘cold spring’affected the overall seed setting rate of walnuts.Which are 95%of the dry matter in the fruit of the species fond of ligh,were produced by the photosynthesis of the leaves.The photosynthetic capacity reflected the ability of the walnut to respond to changes in the surrounding environment.This study selected‘Chandler’,‘Qingxiang’,‘Xiangling’,‘Xiluo NO.2’,‘Wen185’,‘Yuanfeng’,‘Vina’,‘Shanhe NO.5’,‘Xiluo NO.3’,‘Chico’,‘Jing861’planted in Longnan District of Gansu Province.Then the walnut shoots were placed in a low temperature control chamber at 0℃for low temperature treatment 24 hour.simultaneously,we measured through color-developing method,ultraviolet absorption methods,nitroblue tetrazolium photoreduction method and other methods removed the buds from walnut branches and test the content in different varieties of walnut proline（Pro）,soluble sugar（SS）,soluble protein（SP）,malondialdehyde（MDA）,and peroxidase（POD）,superoxide dismutase（SOD）,catalase（CAT）.Then we according to the index of each physiological index corresponding and comprehensive score to the size of sorting,by clustering analysis to classify 11 varieties of walnut.The photosynthetic characteristics of walnuts were selected from the end of summer in August in Longnan.By using an automated light curve program in the LI-6400portable photosynthesis analysis system（LI-COR,Lincoln,Nebraska,USA）,the authors analyzed the differences of light saturation point（LSP）,light compensation point（LCP）,net photosynthetic rate（Pn）,maximum net photosynthetic rate(Amax),dark respiration rate（Rd）,intercellular CO2 concentration（Ci）,stomatal conductance（Gs）,transpiration rate（Tr）,apparent quantum yield（AQY）and other parameters in11 walnut cultivars.The differences in photosynthetic response among different walnut varieties were discussed,which provided a theoretical basis for efficient planting in Longnan.Get the following conclusions:It turn out that the cold hardiness of 11 walnut varieties by using principal component analysis from strong to weak were‘Chandler’>‘XiluoNO.2’>‘Chico’>‘Vina’>‘Qingxiang’>‘Jing861’>‘Xiangling’>‘XiluoNO.3’>‘ShanheNO.5’>‘Yuanfeng’>‘Wen185’.According to the membership function value methodwas,‘Chandler’>‘XiluoNO.2’>‘Chico’>‘Vina’>‘ShanheNO.5’>‘Xiangling’>‘Qingxiang’>‘Xiluo NO.3’>‘Wen185’>‘Jing861’.The main component analysis and the subordinate function value showed that excepting three varieties of‘Jing861’,‘Shanhe NO.5’and‘Yuanfeng’,the other eight varieties were basically in the same and the coincidence rate was as high as 72%.In a conclusion,almost the‘Chandler’was not affected by low temperature in early spring as well as‘Xiluo NO.2’,‘Chico’and‘Vina’these three cultivars were less affected by early spring temperatures.‘Shanhe NO.5’,‘Xiangling’,‘Yuanfeng’,‘Qingxiang’treated by low temperature in early spring impact was relatively large and incline to chilling injury in early spring.The results showed that:according to photosynthetic efficiency ranked as followed:‘Vina’>‘Yuanfeng’>‘ShanheNO.5’>‘Chandler’>‘Wen185’>‘XiluoNO.3’>‘Xiangling’>‘Qingxiang’>‘Chico’>‘XiluoNO.2’>‘Jing861’.Among 11 varieties of walnut,the light intensity of‘Vina’adapts to a wide range and was suitable for dense planted in both strong and low light conditions;‘Yuanfeng’and‘Shanhe NO.5’were suitable for close planting under strong light conditions;‘Chandler’has a strong ability to adapt and should be properly planted for high density under strong light conditions;‘Chico’and‘Xiluo NO.2’should be careful to maintain spacing as the light intensity adapted to a narrower range.Among them,‘Chico’was suitable for planting in areas with strong sunlight and‘Xiluo NO.2’was instead suitable for areas with weak light;‘Xiluo NO.3’,‘Qingxiang’and‘Xiangling’were more suitable for close planting under low light conditions,because its weak light utilization efficiency was high.In the 11 varieties,the shade tolerance of‘Jing 861’was the best,which was suitable for close planting in the areas with weak light intensity.The above conclusion can be seen:In the selection and cultivation of local walnuts,‘Chandler’and‘Vina’had strong adaptability to the environment,and the widespread promotion of planted and proper close planted helped fruit production and saved land resources;The‘Chico’,‘Yuanfeng’and‘ShanheNO.5’were not tolerant to cold and should not be cultivated in areas where the temperature difference was large.It was suitable for planted in areas where there was warmth and high light radiation.‘XiluoNO.3’,‘Xiangling’,‘Qingxiang’and‘Jing 861’were shade-tolerant and not hardy.They were suitable for dense planted in dark and warm areas. |
