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Anatomy of Flowering Plants
Question
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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 true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false

Answer

A.

If both assertion and reason are true and reason is the correct explanation of assertion

Heartwood formation occurs spontaneously because it is a genetically programmed process. 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 rendered non - functional. Therfore, heart wood is a modified or non- functional secondary xylem. It is also known as duramen. Sap wood is the functional outer younger rings of secondary xylem. It is also known as alburnum. With the passage of time and addition of new outer rings of secondary xylem due to cambial activity more rings ofthe 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.

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