Study Of The Physiological Mechanism On Occurrence Of Shoot Wilt In Walnut Tree

In the walnut production region of North China,shoot wilt in walnut has become one of the more prominent problems in walnut cultivation,resulting in serious influence on yield and economic benefit of walnut,which seriously restricts the development of walnut industry.’Zhonglin No,1’ walnut was used as material in this study,on the basis of investigating the occurrence of withered shoot in annual shoots in different parts of canopy of different tree forms,analyzing the relationship between the storage reserves content of shoot and shoot wilt,the causes of the differences in storage reserves content of shoot were discussed from microenvironmental climate change and leaf development,with views to clearing the physiological mechanism of shoot wilt and proposing the reasonable tree form that could reduce the shoot wilt in walnut.The results demonstrated that:(1)Withered shoot ratio of different tree forms is the highest in interior canopy,in peripheral canopy the withered shoot ratio is the lowest.Withered shoot ratio of ’Spindle shape’ walnut tree is the lowest,are reduced by 43.1%,38.2%,39.3%than ’Natural round shape’ walnut tree that is the highest in withered shoot ratio in interior canopy,middle canopy and peripheral canopy respectively.(2)Shoot diameter,shoot water content and shoot storage reserves content of different types of shoots of different tree forms are the lowest in interior canopy,in peripheral canopy those are the highest.Shoot diameter,shoot water content and shoot storage reserves content of different types of shoots of interior canopy,middle canopy and peripheral canopy all are the highest in ’ Spindle shape’ walnut tree,in ’Natural round shape’walnut tree those are the lowest.Shoot water content and shoot storage reserves content of interior canopy,middle canopy and peripheral canopy in different tree forms are the highest in shoots with length in<5 cm,in shoots with length in>20 cm those are the lowest.(3)Photosynthetically active radiation,CO2 concentration and air temperature of different tree forms are the lowest in interior canopy,in peripheral canopy those are the highest.Photosynthetically active radiation is the highest in ’Spindle shape’ walnut tree,in ’Natural round shape’ walnut tree the photosynthetically active radiation is the lowest.There are no obvious differences in CO2 concentration and air temperature among different tree forms.Air relative humidity of different tree forms is the highest in interior canopy,in peripheral canopy the air relative humidity is the lowest,there is no obvious difference in air relative humidity among difference tree forms.(4)Net photosynthetic rate,thickness,specific leaf weight,water content and storage reserves content of leaves of different tree forms are the lowest in interior canopy,in peripheral canopy those are the highest.The regularity and closeness on organizational structure arrangement for upper epidermis,palisade tissue,spongy tissue,lower epidermis of leaves of different tree forms are the worst in interior canopy,in peripheral canopy those are the best.Net photosynthetic rate,thickness,specific leaf weight,water content and storage reserves content of leaves of interior canopy,middle canopy and peripheral canopy are the highest in ’Spindle shape’ walnut tree,in ’Natural round shape’ walnut tree those are the lowest.The regularity and closeness on organizational structure arrangement for upper epidermis,palisade tissue,spongy tissue,lower epidermis of leaves of interior canopy,middle canopy and peripheral canopy are the best in ’Spindle shape’walnut tree,in ’Natural round shape’ walnut tree those are the worst.(5)There is significant negative correlation between the withered shoot ratio and the shoot diameter,the shoot water content,the storage reserves content respectively,however,there is no significant correlation between the withered shoot ratio and the shoot length.There is significant negative correlation between the withered shoot ratio and the photosynthetically active radiation,the CO2 concentration,the air temperature respectively,however,there is significant positive correlation between the withered shoot ratio and the air relative humidity.There is significant negative correlation between the withered shoot ratio and the leaf net photosynthetic rate,the leaf thickness,the specific leaf weight,the leaf water content,the leaf storage reserves content respectively.