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Assertion : In woody stems, the amount of heart wood continues to increase year after year.
Reason : The cambial activity continues uninterrupted
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
If the Assertion is correct but Reason is incorrect.
If both the Assertion and Reason are incorrect.
Solution
In woody trees, the central portion of stem is dark in colour. It is hard and tough due to deposition of resins, tannins, gums and formation of tyloses. This central hard portion is called heart wood. It is formed by secondary growth. Due to cambial activity secondary xylem becomes nonfunctional and forms heart wood or duramen. It is more durable and little susceptible to attack of pathogens. The cambial activity continues in this region
