Question

Assertion: In angiosperms, the conduction of water is more efficient because their xylem has vessels.
Reason: Conduction of water by vessel elements is an active process with energy supplied by xylem parenchyma rich in mitochondria.
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
C) If the assertion is a true statement but reason is false.
D) If both assertion and reason are false.

Answer 1

The xylem and phloem are the vascular elements. The former helps in the transport of water and the latter helps in the transport of food. Vessels transport the water from the root to the shoot unidirectionally.

Complete answer: Xylem are the vascular elements that help to transport water in plants. The xylem consists of tracheary elements, which are the principle conductive tissues, distinguished as tracheid and vessel elements.
-Tracheid forms the leading water-conducting element in gymnosperms. These are also seen in angiosperms. But the vessels are the chief water-conducting elements present in the angiosperms.
-The xylem vessels conduct better than the tracheid elements of the xylem. This is due to the connection of adjacent xylem vessels through perforations. The movement of water through xylem tissues is a passive mechanism that is a result of transpiration pull.
-The root possesses a positive pressure and the shoot possesses a negative pressure as a result of transpiration. Hence water flows in the direction of the pressure gradient and the flow is unidirectional.
The parenchyma cells that are present in the xylem help in the storage of various substances.
Hence, the correct answer is option C.

Note: The vessel elements are absent in gymnosperm, exception is Gneophyta, but present in angiosperm. Similarly, sieve elements are also absent in gymnosperm but present in angiosperm.