Mature sclerenchyma cells have
- A.cellulose wall and are living
- B.lignified wall and are living
- C.suberized wall and are dead
- D.lignified wall and are dead
Correct answer
Explanation
The correct answer is D, lignified wall and are dead. Sclerenchyma cells lay down thick walls hardened with lignin, and once the wall is complete the protoplasm dies.
Sclerenchyma is the plant tissue that gives strength and rigidity. It occurs in two forms: long, narrow fibres, found in the stems of jute, flax and hemp, and short, stony sclereids, which make the hard shells of nuts, the gritty texture of a pear and the seed coats of legumes. Because lignin makes the wall waterproof and very thick, the cell cavity (lumen) becomes narrow and the cell no longer lives.
Option A is wrong because thin cellulose walls and living cells describe parenchyma. Option B is wrong because sclerenchyma is not living at maturity; the living supporting tissue is collenchyma, whose walls are thickened at the corners with cellulose and pectin. Option C is wrong because suberized dead walls belong to cork cells, not sclerenchyma.
Exam tip: parenchyma = living, thin wall; collenchyma = living, corner thickening; sclerenchyma = dead, lignified.
Practice Questions
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- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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