sap·wood /-ˌwʊd/
邊材,白木質
Sap·wood n. Bot. The alburnum, or part of the wood of any exogenous tree next to the bark, being that portion of the tree through which the sap flows most freely; -- distinguished from heartwood.
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sapwood
n : newly formed outer wood lying between the cambium and the
heartwood of a tree or woody plant; usually light
colored; active in water conduction