Effects Of High Light Efficiency Tree Shape Of Litchi On Photosynthetic Characteristics Of Canopy And Leaves And Fruit Quality

Litchi(Litchi Chinensis Sonn.)is a subtropical evergreen fruit tree originating from the south of China.The tree body is tall,up to 20 m,the crown is mostly round-headed,and the shoots grow vigorously.The Litchi orchard with 26 plants per acre is managed normally,and it is generally closed after 10-13 years of planting.Increasing with the age of the tree,he degree of confinement of the orchard becomes more and more serious,it is difficult to manage and harvest,difficult to control pests and diseases.There were a series of problems such as low quality and poor fruit quality.In view of the increasingly serious problem of irrational structure of litchi tree,the light condition of the tree is improved mainly by retracting,opening skylight and pruning sparsely of large branch,but the structure and canopy characteristics of the tree after the transformation were lacked to study carefully.It had led to inconsistent in technical specifications and effects.Two kinds of high-efficiency tree shape of litchi(high crown open-center shape and low crown open-center shape)were compared with two kinds of tree shapes commonly used in production(similar round head shape and natural round head shape)in tree structure and crown.Based on the differences in characteristics of crown,photosynthetic characteristics of leaf and fruit quality,the structural parameters of litchi high crown and short crown opened tree were proposed.Based on this,a set of feasible technology and operability were accepted easily by fruit farmers.Technology solution of high-light efficiency tree transformation was put forward.The main results were presented as follows:(1)The high-crown and low-crown two open-center shape tree’s ineffective light areas are significantly smaller than the “open skylight” near-rounded shape and natural round head shape;the distribution of the open-center haped tree’s leaf area index is low in the center of canopy.The round-headed tree shape shows a trend of high center and low circumference.(2)After the tree shape transformation,the low-crown open-center shape and the high-crown open-center shape have a significant change in the tree characteristics compared with the open-skylight shape,and the height of the tree is reduced,and the crown width is obviously increased.In the comparison of the first three branches,the short crown happy shape and the high crown happy tree are significantly smaller than the open skylight near the round head shape,and the opening angle becomes larger.The high-crown natural roundheaded branches are close to the open skylight near the natural round head shape.(3)in the four-season comparison of the leaf area index(LAI),open-center shape is lower than the open-skylight shape,while the scattered radiation transmission coefficient(TCDP)shows the opposite trend;the extinction coefficient(K)and the direct radiation transmission coefficient(TRCP)at the zenith angles of 6.5° and 19.5° show diffirence between opencenter shape and open-skylight shape,while the high crown natural round head canopy characteristic analysis results are similar to the open skylight shape.From five indicators,comprehensive evaluation of the reasonable degree of several tree-shaped canopy characteristics,low crown open-center> high crown open-center>open-skylight> natural round head.(4)The inner layers of the two open-center shape trees have higher net photosynthetic rate than the leaves of the inner layer of the open-skylight shape.The net photosynthetic rate of the natural round head inner layer and the middle layer leaves is close to the open-skylight shape tree.(5)The two happy-shaped trees are significantly higher than the open skylight in comparison of yield.The quality of several tree-shaped outer fruit is not obvious,but the quality of the fruit in the open-center shape tree canopy is obviously better than the round head.(6)According to the results of this study,the structural parameters of the litchi highefficiency open-center shape tree were proposed.The structural parameters of the high-crown open-center shape tree are 3.5-4.5m,the main branch is 3,the opening angle is 55-60°,the first-level side branch is 6 and the second-level side branch is about 12,evenly distributed to the canopy.Peripheral extension;the number of lateral branches without leafy branches is not more than 6 grades,the thickness of chloroplast layer is 1.0-1.2 m;the result is 800-1000 strips of furits branches.The structural parameters of the low-crown open-center shape tree are 3.0-3.5m,the main branch is 3,the opening angle is 60°,the first-level side branch is 6 and the second-level side branch is about 12,evenly distributed to the canopy.Peripheral extension;the number of lateral branches without leafy branches is not more than 5 grades,the thickness of chloroplast layer is 0.8-1.0 m;the result is 450-600 strips of furits branches.