光强对砀山酥梨果实发育期可溶性糖、可滴定酸和V_C含量的影响

Influence of Light Intensity on Soluble Sugar, Organic Acid and Vc Content of Pyrus bretschneideri cv. Dangshan Su Pear Fruit in Its Growth Phase

This study used 40-year-old Pyrus bretschneideri cv. Dangshan Su pear trees in Dangshan County, Anhui Province as experimental materials. Four positions at the crown of the pear tree with different light intensity were observed, including the south exterior and interior and the north exterior and interior of the middle crown. The ZD-ZA illumination meter was adopted to measure the light intensity, the anthracene ketone method to survey the soluble sugar, the standard acid-soda to measure the organic acid, and the 2,6-dichloropheonlinolphenol to survey the Vc. Sampling began in the first week after the anthesis, following a time schedule of one times every two weeks within two months of the prophase of the fruit development, and one times every four weeks of the later period until the fruit ripens. Correlation analyses, variance analyses and multiple comparison were applied to process the data.The results showed that: 1) the soluble sugar level increased with the growth of the fruit, slowly in the initial 7 weeks after the blooming, but rapidly from the 7th week on, and the positive correlation was found between the sugar level and the number of weeks after the anthesis (r=0.961), and between the sugar level and light intensity (r=0.95); 2) the organic acid level presented the trend of falling with the growth of the fruit, and the correlation between the organic acid level (not apparently related to the light intensity) and the number of weeks after the anthesis was negative (r=-0.814); 3) the sugar-acid ratio rose with the growth of the fruit, in positive correlation with the soluble sugar level and not significant correlation with the organic acid level; 4) the variation of Vc content indicated a low-high-low pattern, with the value of 25.76 mg·kg -1 in the first week after the blooming, and a rise to 68.32 mg·kg -1 in the 5th week, then a decline with the fruit growth to 18.82 mg·kg -1 in the 7th week, and the significant correlation was not found with the number of weeks after the anthesis and the light intensity; 5) the light intensity was positively correlated with the soluble sugar, while not significantly correlated with the organic acid and Vc. The quality of fruit was improved with the increase of light intensity.The result suggests that different measures need to be taken to adjust the nutrition of the pear tree in the different fruit-growth phases. When the tree is properly trimmed, sunlight can be fully utilized to achieve a perfect photosynthesis which contributes to a better inner physiological system, and thus the fruit quality will be improved.