What is the difference between heartwood and sapwood

Moreover, sapwood is often light in color when compared to the heartwood. Heartwood and sapwood are the two areas in a cross section of a woody stem. Both types of wood perform a critical function in a tree. What is Heartwood — Definition, Features, Function 2. What is Sapwood — Definition, Features, Function 3. Heartwood or duramen is the inner portion of the woody stem, containing a plugged secondary xylem.

The formation of the heartwood is genetically programmed. With the growth, the stem increases its diameter by forming new xylem and phloem. Therefore, the more centered, old xylem becomes useless. Figure 1: Freshly Cross Section of Laburnum. Then, this part of xylem converts into a part with an essential function to the tree. For that, the cells of the center of the trunk die and chemical compounds accumulate in them. Some of these compounds are resins, terpenes, and phenols. Thus, this gives a dark color to the heartwood.

Also, this gives it the resistance to decay and the ability to avoid insects and fungal infections. Moreover, this allows functional alteration. Hence, the main function of the heartwood is to provide structural support to the tree.

Sapwood or laburnum is the starting form of wood of any tree. It occurs from a thin layer of cells beneath the bark called the vascular cambium , which produces wood cells to the inside and bark cells to the outside.

Overview and Key Difference 2. What is Secondary Growth 3. What is Heartwood 4. What is Sapwood 5. After primary growth lateral meristem becomes active and results in the formation of secondary permanent tissues. This is called secondary growth. The lateral meristems are the lateral vascular cambium and cork cambium. They are formed only on dicots. In monocots, there is no cambium. Therefore, there is no secondary growth. As a result of secondary growth, there is an increase in thickness or girth in stems and roots.

In the stem, the intrafascicular cambium becomes active and cut off cells to the outside and inside. The cells that cut off to the outside become the secondary phloem. The cells on the inside become the secondary xylem.

In the meantime, parenchyma cells between adjacent vascular bundles also become meristematic and form the interfascicular cambium. The intrafascicular cambium and the interfascicular cambium join to form a cambial ring which is the vascular cambium.

The interfascicular cambium cuts off cells to the outside and inside. But as the tree gets older and its trunk increases in diameter, things change. No longer is the entire cross-section of the trunk needed for conducting sap. This, combined with an increased need for structural support, causes significant changes in the wood.

The cells nearest the center of the trunk die, but they remain mostly intact. As these older sapwood cells age and die, they become heartwood. That is, they are altered to accommodate a shift in function. As residues of the once-living cells and additional chemical compounds from elsewhere in the plant accumulate in the heartwood, those cells cease to transport water or store energy reserves. These compounds including resins, phenols, and terpenes, sometimes referred to as extractives not only help make heartwood more resistant to attack by insects and decay organisms but also tend to give this inner portion of the stem a distinctive darker color.

For example, the famous dark brown of black walnut lumber and the striking red hues of black cherry boards occur only in the heartwoods of these trees, and both owe their characteristic colors to these chemicals.

Such woods are highly prized largely because of their colored heartwoods, but it is important to remember that color alone is not the sole distinction between sapwood and heartwood, regardless of species.

Indeed, wood can be colored for reasons unrelated to heartwood. There are many discolorations associated with injury or fungal infection of wood, for example, and some heartwoods — including that in most spruces, fir, cottonwood, and basswood — are naturally very light colored.

Then again, if these light-colored heartwoods are injured, they often do become darkened by discoloration. So, in summary, sapwood, which is nearly always light colored, results from new wood formation. Heartwood, which is often — but not always — dark colored, results from the natural aging process of the tree. But both can be discolored by many other causes.

Typically there is less sapwood than heartwood in any given stem. The exception, of course, is in young trees and the youngest portions of stems and branches on older trees which — because they are young — are naturally dominated by sapwood.