The heartwood can be seen mainly on older stems. While the sapwood comprises the younger layers of wood. It means that it is the first wood in the trees.
The sapwood is the softest external part of the woody stem. While the heartwood is a hard central part or internal part of the sapwood.
The heartwood deposited with certain compounds, such as gums, tannins, oils, resins, is darker in color. On the other hand, sapwood without deposition of such materials has lighter colors.
The sapwood is driving the wood, as it drives the sap (fluid containing dissolved minerals and water) between the roots and the crown of the tree. Also, keep some of them on rainy days. The heartwood is not conducive due to blocked intercellular spaces.
The heartwood has negligible intercellular spaces in relation to the cells, which are blocked mainly with dead material, that is, lignin. The sapwood has enough intercellular spaces for its cells to help it conduct materials.
The sapwood, soft and without deposition, is susceptible to decomposition and attack by insects. While Heartwood is very resistant to attack and decomposition of insects.
Sapwood provides nutrients, water, and minerals in the form of sap to various parts of the plant. The heartwood supports the plant.