Which one of the following statements is correct ?
- A.Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres.
- B.Flexibility in plants is due sclerenchyma.
- C.Parenchyma have no intercellular spaces.
- D.Xylem consists of sieve plate, sieve tube and companion cells.
Correct answer
Explanation
The correct answer is A: xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres. These four elements make up the complex tissue that carries water and minerals upward from the roots.
Tracheids and vessels are long, dead, thick-walled tubes through which water moves; xylem parenchyma is the only living part and stores food; xylem fibres give support. Phloem, the other complex tissue, carries food and is made of sieve tubes, companion cells, phloem parenchyma and phloem fibres. Among the simple tissues, parenchyma has thin-walled cells with large spaces between them, collenchyma gives flexibility, and sclerenchyma, with dead, thickened cells, makes plants hard and stiff, as in a coconut husk.
B is wrong because flexibility comes from collenchyma; sclerenchyma gives rigidity.
C is wrong because parenchyma cells are loosely packed with large intercellular spaces.
D is wrong because sieve tubes, sieve plates and companion cells belong to phloem, not xylem.
Exam tip: xylem carries water (tracheids, vessels); phloem carries food (sieve tubes, companion cells); collenchyma gives flexibility, sclerenchyma rigidity.
Practice Questions
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- C.1 only
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- B.Elimination reaction.
- C.Addition reaction.
- D.Free-radical polymerization.
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- C.a deflecting force towards west direction.
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Show answer
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