AIIMS2016BotanyAnatomy of Flowering Plants
As secondary growth proceeds, in a dicot stem, the thickness of
Options
- Asapwood increases
- Bheartwood increases
- Cboth sapwood and heartwood increases
- Dboth sapwood and heartwood remains the same.
Correct answer
B. heartwood increases
Step-by-step solution
In a woody stem, due to secondary growth, secondary xylem constitutes the bulk of the stem and is commonly called wood. The secondary xylem consists of vessels, tracheids, wood parenchyma and wood fibres. Width of secondary xylem increases continuously with the age of the plant. In older stems, the wood (or secondary xylem) gets differentiated into two zones - the outer light coloured younger sapwood and the inner darker older heartwood. The xylem vessels and tracheids of heartwood become non-functional because the