Effects Of Altitude On Bud Differentiation In Guanxi Pomelo

Attempt to search out the right time and offer a reference at urging flowerbud of different altitude’s Guanxi pomelo by the means of girdling and sprinkling paclobutrazol. This research focuses on diameter growth of spring shoot, flowerbud investigation, process of flowerbud differentiation and carbohydrate content variation in low altitude(100m), intermediate altitude(300m) and high altitude(500m). The results are followed:1. The results showed that the lateral buds on spring shoot from 1-8 can germinate into flower, even more, located on the first four ones. Delicate shoots can not easily form flower bud, there is a correlation between the diameter and the number of bud germination of branch.2. The diameter of spring shoot is a gradually increasing tendency in these three altitudes. The diameter growth rates are increased then decreased, reach a peak before October 27th, separately step into low increasing stage(less than 2%) in turn delayed 7 days from then on.3. Frozen section is applied to investigate the flower bud differentiation process of Guanxi pomelo, comparing the morphological characteristics in different stages. The result shows that there are few buds start differentiating at the end of September, some growing points begin change coniform to arc shape, circle to plain and wide, as a result, flower primordium appears. The differentiation rates of low, intermediate, high altitude all increased gradually, the differentiation speeds of them are as high as they are ranged in turn. In the differentiation rate of 50%, low, medium and high altitude to delay 7 days one after the former.4. Until October 20th, the low altitude firstly appears few sepal primordiums formed on growing points, intermediate and high altitudes’ sepal primordium is formed later about 1 to 2 weeks. In low, intermediate and high altitudes, the sepal differentiation rate of which is higher than the later one.5. The contents of soluble sugar and starch in leaf and branch under different altitudes own the similar variation tendency. Decreasing in the front stage, till October 27th reach the bottom, increasing later, ended on November 10th, after then, gradually decreasing again.