the older inactive central wood of a tree or woody plant; usually darker and denser than the surrounding sapwood
同义词：duramen
heartwood详细解释
heart.wood n.（名词）The older, inactive central wood of a tree or woody plant, usually darker and harder than the younger sapwood.Also called duramen 心材，树干：树木或木本植物中较老的不再生长的部分，通常比树龄短的边材更硬且颜色更深也作 duramen
