Abstract:

Pyrus pyrifolia 'Sunhwang was used as experimental material.the canopy structure characteristics and photosynthetic capacity were comparatively investigated among the horizontal trellis system, V-shaped system and the sparse shaped canopy with WinsCanopy2005a and photosynthetic analyzer.The sugar content and activities of the sorbitol-invertase were measured during the fruit development stage to determined.It studied the effects of tree shape on the sugar accumulation process and activities of sorbitol-invertase in fruits. The results showed that canopy openness and photosynthetic photon flux density (PPFD) were significantly higher in Horizontal trellis system than that in the other two tree shapes.The light transmittance and photosynthetic capacity in Horizontal trellis system was the best among the three tree forms. Contents of the soluble sugar,starch,glucose,fructose, sucrose,sorbitol and the activities of sorbitol-invertase were the highest in the fruit of the level-shaped system,following by V-shaped system, and then the Sparse shaped canopy. The differences were significant.The accumulation sugars in the fruit mainly were starch and sorbitol at the early development stage and fructose at the late stage.The activities of SDH and SOX increased gradually in the fruit from early to middle development stage and decreased at the late stage but still were higher than that in prophase.

Key words: Pyrus pyrifolia &lsquo, Sunhwang&rsquo, tree shape, sugar accumulation, sorbitol, invertase