NEET Biology Notes Anatomy of Flowering Plants Wood
Wood is cellular and contains all tissues inner to cambium, i.e. secondary xylem and pith. The central, hard, tough and darker region of wood constitutes heart wood, while peripheral portion constitutes the sap wood.
Dicot wood is extremely variable; certain species lack some of these cell types, other species have them all. The relative amount of each cells vary greatly. The wood of gymnosperms is called softwood or non-porous wood, whereas wood of angiosperms is called hardwood or porous wood.
Spring wood plus autumn wood of a year constitute annual ring. Annual rings are conspicuous in temperate (cold) regions. The age of tree can be determined by counting annual rings in basal portion of tree trunk. The calculation of age of the tree by counting annual rings in called dendrochronology