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Which of the following is formed first?
 

Option: 1

Sapwood


Option: 2

Heartwood


Option: 3

Both are formed together


Option: 4

None of these are formed

 


Answers (1)

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  • When a transverse section of a woody trunk is taken, two regions are distinctly visible.
  • In the centre, there is dark coloured wood called heartwood. 
  • Heartwood is made up of dead and non-functional components of wood. 
  • Heartwood is also called duramen.
  • The lumen of vessels in the heartwood has been blocked by tyloses.
  • Tyloses are balloon-like structures formed due to protrusion of xylem parenchyma cells into the lumen of vessels.
  • These parenchyma cells become lignified and dead, thereby making the vessels non-functional.
  • In the tracheids of gymnosperms, the tylosoids are present.
  • The heartwood is durable and resistant to parasitic and microbial attack. 
  • It gives mechanical support to the tree trunk.

All wood in a tree is first formed as sapwood. Some part of it is later blocked by the tyloses resulting in the formation of heartwood.

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Gunjita

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