Studies On Responding Mechanism Of Root Pruning In Autumn And Its Interactive Effects With Nitrogen Application In Apple Tree

To understand responding mechanism of root pruning in autumn and the influence ofinteractive effects with nitrogen application on growth in apple tree. The3years old youngFuji potted apple（Malus×domestica Borkh.）trees were used as the experiment materials.Taking measures of root pruning on both sides of the trees, using high performance liquidchromatography (HPLC), stable isotope15N traced and other methods, we analyzed thechange of carbohydrate ingredients, contents and related SPS,SS,AI, NI,α-amylase andβ-amylase activity in annual phloem, perennial phloem and roots; we analyzed the change ofstable isotope15N absorption and transportation in different parts after root pruning; at thesame time, we analyzed the effect of root pruning and fertilizing interactions on root length,root volume, root length density, root length of different diameters, the growth andphotosynthesis in young apple trees. The results can be described as follows:1. Sucrose and sorbitol contents increased significantly in annual phloem, perennialphloem and roots after root pruning in autumn, while glucose and fructose changed little inannual phloem and perennial phloem. After root pruning in autumn, total soluble sugar inroots was significantly higher than control in autumn; a high contents of total soluble sugar inannual phloem and perennial phloem and a low contents of total soluble sugar appeared inroots before spring germination; a low contents of starch in annual phloem and perennialphloem and a high content of starch in root. At the same time, the SPS, SS, AI and NIincreased significantly in annual phloem, perennial phloem and roots before the germinationof spring after root pruning in autumn, while the amylase had a little change.2. Root pruning in autumn made the total nitrogen and total nitrogen content reduced inannual branches and leaves of young apple trees. while the total nitrogen and total nitrogencontent of perennial shoots phloem and xylem lower than not root pruning. After root pruning, there was a low of the15N distribution tendency in annual branches and leaves and a high of15N distribution tendency in roots. Root pruning also made the distribution rate of15N reducedin annual branches and leaves and made the distribution rate of15N increased in root. At thesame time, root pruning also caused lower total absorption to15N and lower fertilizerutilization efficiency than not root pruning.3. Root pruning and fertilization integrated treatment in autumn increased root length,root length density and the number of root tips; increased root surface area and root volumereduction, increased the root length≤1.0mm diameter, reduced the root length of＞1.0mmdiameter. Simultaneously, root pruning and fertilization integrated treatment in autumn madethe net photosynthesis of root pruning and fertilization treatment increased by13.3%thancontrol, while transpiration rate decreased by2.3%, water use efficiency improved by15.2%.In addition, root pruning and fertilization treatment also reduced the number of longbranches, increased the number of spur, the ratio of root to shoot and the average leaf area.Roots pruning in autumn increased the accumulation of sucrose, sorbitol and solublesugar and increased the related enzyme activity of carbohydrate. After root pruning in autumn,the15N distribution tendency and distribution rate of new shoots decreased, while the15Ndistribution tendency and distribution rate of root increased. At the same time, root pruning inautumn can reduced the total nitrogen absorption and fertilizer utilization efficiency of theyoung apple trees. But root pruning and fertilization treatment in autumn could significantlyimprove the photosynthesis of the young apple trees, decrease the plant’s root systemredundancy, and increased the number and length of fine roots. Root pruning and fertilizationtreatment in autumn played an important role in inhibiting vegetative growth and increasingthe number of spur.