SAPWOOD
sapwood
(noun) newly formed outer wood lying between the cambium and the heartwood of a tree or woody plant; usually light colored; active in water conduction
Source: WordNet® 3.1
Etymology
Noun
sapwood (countable and uncountable, plural sapwoods)
The wood just under the bark of a stem or branch, different in color from the heartwood.
Synonyms
• alburnum
Antonyms
• heartwood
Source: Wiktionary
Sap"wood`, n. (Bot.)
Definition: The alburnum, or part of the wood on any exogenous tree next to
the bark, being that portion of the tree through which the sap flows
most freely; -- distinguished from Heartwood.
Source: Webster’s Unabridged Dictionary 1913 Edition