| The formation of widespread water-fluctuation-zone in Three Gorges Reservoir Region will affect the eco-environment of this region. Vegetation construction can stablish banks and control soil erosion. As an important plant species to be chosen for constructing the vegetation in this region, Salix variegata has strong flooding resistance and is widespread in Three Gorges Reservoir Region. Energy supply in plants affects their endurance of flooding tremendously while carbohydrate reserve in plants determines their energy supply directly.In this paper, carbohydrates were divided into three groups according to their dissolvability. The concentrations of these carbohydrates in organs of S. variegata exposed to different flooding treatment were determined. The changes of plant height, total leaf number and branch number before and after flooding were analyzed and the sprout of new leaves and branches after flooding were observed in order to know the flooding resistance of S. variegata in detail.Experimental results are as follows:(1) Leaves shed during flooding;the upward growth of submerged plants slowed down while the intermittent partial flooded plants showed even faster up growth;the flooded plants ceased their root biomass accumulation and slowed down their stem biomass accumulation.(2) Ethanol soluble sugars were evenly distributed in organs of plant;content of watersoluble polysaccharides and starch was lowest in roots and highest in leaves. Roots contain mainly ethanol soluble sugars and starch;stems contain mainly water soluble polysaccharides and starch;leaves contain mainly starch.(3) For continual flooding, ethanol soluble sugars content changed following different flooding;after 90d of partial flooding and 0.5m submergence, water soluble polysaccharides in stems were lower than that in control plants;starch content in leaves of 60d flooded plants was lower than that in control plants. For intermittent flooding, non-structure carbohydrates in plants changed unevenly following different flooding, but there are still enough carbohydrates available for S. variegata.(4) To discuss the resilience of S. variegata after flooding, growth of apical and lateral bud in this plant was analyzed. It was found that there was significant difference in lateral bud growth among different flooding stress: for plants suffered the same flooding duration, the deeper the water depth, the less the new branches appeared;the longer the flooding term, the more the new branches appeared and the later the difference among water depth was found. The effect of flooding on apex growth of each branch was not significant: there was no significant difference of new leaf number per branch among different flooding treatment and the apex growth was normal after flooding.In conclusion, carbohydrate reserve is sufficient for S. variegata to get through long term flooding. And S. variegata has great capacity to recover from flooding quickly.
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