Question

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

• A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion
• B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion
• C. If Assertion is true but the Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (A)

As a result of continued secondary growth for several years, the older parts of the stem and its old branches have a part of its secondary xylem renderd non functional. Such a modified and nonfunctional secondary xylem is called the heart wood or duramen, the functional outer younger rings of secondary xylem constitute the sap wood or alburnum. With the passage of time and addition of new outer rings of secondary xylem more rings of the sap wood are changed into heart wood. This leads to the increase in the thickness of heart wood, whereas the sap wood remains of about the same thickness.