Question

Assertion :In woody stems, the amount of heart wood continues to increase year after year. Reason: The cambial activity continues uninterrupted.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.

Formation of wood starts as sapwood just under the bark. The process is activated by cambium which produces bark cells to the outside and wood cells to the inside. In young trees and in younger parts of older trees, generally, the stem is entirely sapwood. However, as the tree matures, not all cells are involved in conducting sap. The cells nearest the center of the trunk die, remain intact and they become heartwood. The heartwood, therefore, contains all the residues of the dead sap wood along with additional chemical compounds such as resins, phenols and terpenes and provides the structural support required for the growing tree. Further, the increase in girth of the tree stems during its growth each year is because a new layer of wood cells is added inside during the uninterrupted cambial activity.

Therefore, the correct answer is option A.