Question

When one wood is lighter in colour with lower density, the other wood is darker with higher density. They are;
A. Springwood and autumn- wood
B. Heartwood and late wood
C. Springwood and early wood
D. Sapwood and spring wood
E. Autumn wood and springwood

Answer 1

Early wood and late wood concept is that the part of the wood that is formed later in the growing season is latewood; it has smaller and thicker cell walls. The early wood that is formed earlier in the growing season has thinner walls and larger cells. Earlywood is called springwood and latewood is autumn wood.

Complete answer:
Density of wood varies and it basically depends on cambium as we know wood is secondary xylem and secondary xylem is made from cambium. In monocots we know there is no formation of secondary xylem so we will see dicot stems.

In the dicot stem there are vascular bundles present having phloem upwards and xylem downwards and cambium is present in between both. Cambium makes secondary xylem and secondary phloem. In the spring season cambium is more active and less active. In the autumn season this makes different types of cell and cell walls and that’s why density varies.

In springwood when cambium is more active cells are formed that are larger and have wide lumen and make the cell wall thin. These have less amount of xylem fibres that are present in secondary xylem and due to this reason density of spring wood is less.

In autumn wood or late wood that is made in autumn season the cambium is less active and forms cells with small lumen and thick cell wall. The size of cells is small and the amount of xylem fibres that are formed in the secondary xylem is higher in autumn wood. This accounts for the higher density of the autumn wood.

Hence, the correct answer is option (A).

Note: Sapwood is the outer layer of the wood that is still living. It has light colour and has high density. Heartwood is the central wood of the tree that is dead not living. It is also called duramen.