Leaf Potential Productivity at Different Canopy Levels in Densely-planted and Intermediately-thinned Apple Orchards

作     者：SUN Ying ZHANG Yin JIANG Yuanmao SONG Kai GAO Juhong ZHANG Dingyou ZHANG Jixiang 

作者机构：State Key Laboratory of Crop BiologyNational Research Center of Apple Engineering and TechnologyCollege of Horticultural Science and EngineeringShandong Agricultural University College of Science and InformationQingdao Agricultural University Liaocheng Meteorological Administration 

出 版 物：《Horticultural Plant Journal》 (园艺学报（英文版）)

年 卷 期：2016年第2卷第4期

页      面：181-187页

学科分类：09[农学] 0902[农学-园艺学] 090201[农学-果树学] 

基　　金：supported by the National Modern Apple Technical System Program of the China Ministry of Agriculture(CARS-28) National Major Program of Research and Development Plan(2016YFD0201100) the‘12th Five-years Plan’National Science and Technology Support Project in Rural Areas(2011BAD32B03-02) the Natural Science Foundation Project of Shandong Province,P.R.China(ZR2009M015) 

主　　题：photosynthetically active radiation(PAR) maximum carboxylation rate(CEmax) leaf nitrogen content(N1) maximum electron transfer rate(Jmax) specific leaf weight(M1) 

摘      要：Most apple orchards in the apple production districts in China were densely planted with vigorous rootstocks during the 1980 s. These orchards have suffered micro-environmental deterioration and loss of fruit quality because of the closed canopy. Modification of the denselyplanted orchards is a priority in current apple production. Intermediate thinning is a basic technique used to transform densely-planted apple orchards in China. Our goal was to provide theoretical basis for studying the effect of thinning on the efficiency of photosynthetically active radiation(PAR),fruit quality, and yield. We measured leaf area, solar radiation, and leaf air exchange at different tree canopy levels and by fitting relevant photosynthetic models, vertical distribution characteristics of leaf photosynthetic potentials and PAR were analyzed in various levels within canopies in densely-planted and intermediately-thinned orchards. Intermediate thinning significantly improved the radiant environment inside the canopies. PAR distribution within the canopies in the intermediately-thinned orchard was better distributed than in the densely-planted orchards. The invalid space under 30.0% of relative photosynthetically active radiation(PAR_r) was nearly zero in the intermediately-thinned orchard; but minimum PARr was 17.0% and the space under 0.30 of the relative height of the canopy was invalid for photosynthesis in the densely-planted orchard. The leaf photosynthetic efficiency in the intermediately-thinned orchard was improved. Photosynthetic rates(P_n) at the middle and bottom levels of the canopy, respectively, were increased by 7.80% and 10.20% in the intermediately-thinned orchard. Leaf development, which influences photosynthetic potential, was closely related to the surrounding micro-environment, especially light. Leaf photosynthetic potentials were correlated with leaf nitrogen content(N_1) and specific leaf weight(M_1) at various levels of canopies. Compared with the densely-plan