Question

Which of the following statements is true?

Answer 1

The function of xylem tissue is to transport water and minerals from roots to other parts of the plants through tracheids and vessels. Both of these xylem tissues are also known as tracheary elements. The cells of tracheids and vessels die at maturity, have lignified walls, and are present in both primary and secondary xylem.

Complete answer:
-Vessels are made by a series of cells present longitudinally with their separating walls dissolved. Due to the deposition of lignin, the wall of the vessels is thick. The protoplast is absent at maturity and hence is dead with a large lumen.
-Tracheids are unicellular elements while vessels are multicellular. Tracheids are more lignified and hence have a narrow lumen while vessels have less lignified and have a wide lumen.

Properties	Tracheids	Vessels
Presence	In all vascular plants	In angiosperms
Type of cells	Unicellular, Imperforated	Multicellular, Perforated
Cell wall	Thin	Thick
Connection	Lateral	End to end
Cross-section	Polygonal	Circular
Water conduction	Inefficient	Very efficient
Lumen	Narrow	Wide
Cell length	1 mm	10 cm
Surface to volume ratio	High	Low
End walls	Tapering	Transverse or diagonal
Pits	Less large pits	Large small pits

So, the correct answer is option C.

Additional Information:
Tracheids provide structural support in softwoods as they are the major cell type. Tracheids have a higher surface-to-volume ratio as compared to the vessel elements. They work to hold water against gravity by adhesion when transpiration is not taking place. This is the one mechanism that helps plants in preventing air embolisms.

Note: In secondary xylem, the xylem is produced as the stem thickens rather than when it first appears. A vessel element originates from the vascular cambium. A long cell which is oriented along the axis of the stem is known as a fusiform initial. It divides the secondary xylem along its length and forms new vessel elements.