What is wood? What are its different types?
A secondary xylem is called wood. It is obtained by the metabolism of the plant i.e. secondary growth by cambium. It contains the bulk of the plant body in the dicot stem & dicot root. Wood can be classified into the following categories. (i) Hardwood:- Angiosperms produce hardwood. It consists mainly of xylem vessels and thus it is called porous wood. (ii) Softwood:- Gymnosperm produces softwood. It consists mainly of xylem tracheids and thus it is called non-porous wood. (iii) Heartwood:_ It is formed during secondary growth. It contains dead cells. The cells are dark in color as they contain extractives like gums, resins, tannins, etc. (iv) Sapwood:_ It is formed during secondary growth and also it is a peripheral part of the plant. It contains living cells. The cells have light colors as the extractives are absent. (v) Earlywood:- This wood formed during a favorable season. Vessels & tracheids formed are larger in dimensions. (vi) Latewood:- This wood formed during unfavorable seasons. The vessels & tracheids obtained are smaller in dimensions
