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6.Anatomy of Flowering Plants
medium
$I.$ It is resistant to microorganisms
$II.$ It comprises dead elements
$III.$ It comprises highly lignified cell wall
$IV.$ It is the peripheral part
$V.$ It is dark and tough
Which of the above property doesn't belongs to heart wood?
A
$I$ and $II$
B
Only $IV$
C
Only $V$
D
$III$ and $I$
Solution
Only $V$.
In old trees, the greater part of secondary xylem is dark brown due to the deposition of organic compounds like tanins, resins, oils, gums, aromatic substances and essential oils in the central or innermost layers of the stem. These substances make it hard, durable and resistant to the attacks of microorganisms and insects. The region comprises dead elements with highly lignified walls and is called heart wood
Standard 11
Biology
