Chemistry of Heartwood Formation

Abstract

When a tree reaches 10 years of age, heartwood is formed in the central parts of stem and branches. The characteristics of heartwood greatly affect the properties of the wood, such as color tone, order and durability, which are very important in practical use. In addition to these, the botanical scientific interest in the understanding of the significance of a tree’s forming of heartwood and also in the clarifi- cation of the mechanism of heartwood formation have long drawn the attention of researchers to re- search on heartwood and heartwood formation. Heartwood formation is a complicated physiological tree phenomenon involving biological, chemical, and physical changes. Among them, the materials unique to heartwood, specifically, generated and accumulated heartwood extractives, are the conse- quences of chemical changes. As these chemical compounds often have their own properties of color, order and antibiotic activity, the phenomenon at the time of heartwood formation is the most remark- able change phenomenon, so that it can be directly related to the expression of the wood properties. In this review article, heartwood formation is explained mainly through “the accumulation of heart- wood extractives” from physiological, biochemical, histochemical and molecular biological viewpoints. Keywords