Question

Assertion: In woody stems, the amount of heartwood 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

Sap wood has been steadily turned into heartwood. The thickness of heart wood increases due to this conversion.

Complete answer:
First we should know about heartwood to answer this question. Heartwood is also referred to as duramen, dead trees, core wood. The cells normally contain tannins or other compounds that make them dark and often aromatic in colour. Heartwood is physically sturdy, decay-resistant, and less readily penetrated than other wood types by wood-preservative chemicals. One or maybe more living and functional layers of sapwood cells are transformed to heartwood.
Now, let us find the solution from the options-
As a consequence of continued secondary development for many years, the older portions of the stem and its old branches have a portion of its secondary xylem made non-functional, Such a non-functional and modified secondary xylem is said as the heart wood or duramen, the sap wood or alburnum is constituted by the functioning outer younger rings of secondary xylem.
With the passing of time and the introduction of new secondary xylem outer rings due to cambial activity, more sap wood rings are converted into heart wood. This results in a rise in the thickness of the heart wood, while the thickness of the sap wood wood remains approximately the same.
The assertion and reason are both true and the explanation is the best justification of the assertion.

Thus, the correct answer is option A Both Assertion and reason are correct and reason is the correct explanation for Assertion

Note: The central portion of the transverse trunk segment is darker in colour than the peripheral wood of many tree species. This inner section is named heartwood, and the sapwood of the surrounding field. Sapwood contains the younger growth rings and is involved in a tree's life cycles. The older inner layers no longer engage in the transport and storing of water and nutrients and become heartwood as the diameter of the tree increases with maturity.