The Characteristic Of Canopy Structure And Light Distribution In Three Tree Systems Of 'Sunhwang' Pear

The canopy structure characteristics and quality differences were comparatively investigated among the V-shaped system,Horizontal trellis system and Delayed-open central leader system of'Sunhwang'pear(Pyrus pyrifolia Nakai Sunhwang)tree with WinsCanopy2005a and LI-6400 for hemispherical image analysis. Some significant results have obtained as the followings:1.The investigation revealed that the WinsCanopy2005a for hemispherical image anaysis instruments can use to analyze the characteristic of structure in pear tree and evaluate the canopy of pear tree,the LAI2000-Log series method with WinsCanopy2005a was reconunended when evaluating the pear trees.The results showed that Canopy openness,MAL and LAI have a significant relationships with PPFD,but it's different among the tree samples.2.The digital diagnostic index of structure and light in pear tree canopy were as follows(on average):The canopy openness and PPFD in Horizontal trellis system were significantly higher,but the LAI were significantly lower than that in the others. Canopy openness 28.25%,LAI 2.54,MLA 32.70°,direct PPFD under tree 16.24μmol·m-2·s-1,indirect PPFD under tree 2.49μmol·m-2·s-1,total PPFD under tree 18.73μmol·m-2·s-1.3.The tendency of photosynthetic rate in each part of tree canopy was that the upper and external leaves had the highest rate, and rates of leaves in middle canopy were better than in lower and inner. Light distribution in different tree canopy showed similar variation, it was that illumination decreased gradually from top to bottom, from the outside to inside. The tree shape of'Sunhwang' and inherent characteristic of photosynthesis in leaves of'Sunhwang' had not significant difference.The photosynthetic ability of leaves on long branch was higher than short branch's.The photosynthetic ability of leaves on short branch which had fruits was higher than which had no fruits. 4.Among three type orchards,the total PPFD under tree of horizontal trellis system was the best,the yield and quality in V-shaped system were better than the horizontal trellis system and delayed-open central leader system. Single fruit weight, total contents of soluble solid and sugar, and sugar-acid ratio of V-shaped system and horizontal trellis system were higher,whereas, titratable acidity and stone cell contents were lower in comparison delayed-open central leader system. Consistency of fruit quality in different positions of V-shaped system was the best. The weights of single fruit of V-shaped system and horizontal trellis system'Sunhwang'were consistent,and their percent rate of high quality fruit was higher than that of delayed-open central leader system because of higher solar energy use efficiency.5.From this study,we got the common characteristic of pear tree canopy in DeYang of sichuan province,we think horizontal trellis structure was the most suitable one to be taken used to plant in the hot and humid region of Sichuan provience.