Effect Of Root Pruning And Drought On Growth And Rhizosphere Of Young Apple Tree

Controlling vegetative growth of the acrial part is an important work in fruit production, both root pruning and water stress are all effective measures in suppressing the vegetative growth of fruit trees. In Loess Plateau, most apple orchardsare distributed in arid or semi-arid area. But there was no study has been done on the effect of root pruning and water stress on apple tree growth, carbohydrate, and rhizosphere. The present study was established to determine the effect of root pruning and drought on the growth, phytohormone and carbohydrate, and rhizosphere of 2-year-old apple tree. The results are showing that:Water stress decrease the photosynthetic rate(Pn), transpiration(Tr), stomatal conductance(Gs), and intercellular CO2(Ci), but no significant difference was found by root pruning. Root pruning strongly stimulated new root growth, but water stress is not good for new root growth. The effect of root pruning and drought on new shoot and leaf biomass, new shoot length and thickness, leaf length, width and area are in a same variation: T0> T1> T2> T3.In the beginning, root pruning raised the starch content of leaf and new shoot phloem, but decreased the branched phloem, stem phloem, thick root phloem, and fine root starch content. The leaf, new shoot phloem, branch phloem, and thick root phloem also increased after root pruning. In most stages, water stress reduced the branch phloem, stem phloem, thick root phloem, and fine root phloem starch content.Root pruning and water stress all improved the nitrogen, and decreased phosphorus and potassium use efficiency in the rhizosphere. In the normal water station, root pruning decreased available nutrient, but increase under drought condition. In the early stage, root pruning enhanced the medium invertase, catalase and urease, but the medium alkaline phosphatase was lower. The apple rhizosphere bacteria increased significantly after root pruning, but water stress highly significantly decreased bacteria. Growing in good moist substance, the actinomycetes and fungus increased after root pruning, after 18 th May, they decreased significantly. But under drought condition, actinomycetes and fungus always increased. Water stress reduced the bacteria, actinomycetes, and fungus in the apple rhizosphere under drought condition, and root pruning can alleviate the negative effective of water stress.