Assertion: The greater part of secondary xylem is lighter in colour and consists of dead elements with highly lignified walls and is called heartwood.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. if both assertion and reason are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false.
D. if both assertion and reason are false.

Answer

D

Explanation

In old trees, the greater part of econdary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils in the central or innermost layers of the stem. This region comprises dead elements with highly lignified walls called as heartwood. The peripheral region of the secondary xylem is lighter in colour and is known as the sapwood.