Question

Annual ring involves:
A. Earlywood and latewood
B. Heartwood
C. Sapwood
D. None of these

Answer 1

Various tissues perform specialized functions. The wood of low density usually produced early in the season is called “earlywood.” On the other hand, the part of the annual xylem increment that is produced late in the growing season is called “latewood.”

Complete step by step answer: The meristematic tissues are specialized tissues which are actively dividing cells present in the region of active cell division called meristems. Some cells in plants lose their ability to divide. and are termed as permanent tissues. These are also of two types; simple and complex. The growth of the roots and stems with the help of apical meristems is called the primary growth. When the plants exhibit an increase in girth along with the increase in length, this growth is called the secondary growth. The layer which is responsible for the creation of cutting off vascular tissues is called vascular cambium. Also, in the young stems, vascular tissues are present in patches. In secondary growth, these join with each other and form a complete cambial ring later. The activity of cambium is influenced by many physiological and environmental changes. In the spring season, the cambium is active and produces a large number of xylary elements such as vessels having a wide lumen. Therefore, the wood formed in this season is lighter in colour having low density and called as spring wood or earlywood. In contrast, the wood in the winters is less active and forms very few xylary an element having narrow vessels, this type of wood is darker in colour and has high density, called as autumn wood or latewood. Subsequently, two types of concentric rings are seen in the wood. These are referred to as the annual rings. Annual rings give the estimation regarding the age of the plant or tree.
Therefore, the correct answer is option A.

Note: In dicot plants, the cells of cambium present in primary xylem and primary phloem is the intrafascicular cambium. When the cells of medullary rays (the cells joining the patches of xylem and phloem) become meristematic, these form interfascicular cambium and consequently a continuous ring is formed. This cambial ring is responsible for further formation of secondary xylem and secondary phloem.