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Question 52
Give reasons for

(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole.
(b) Intercellular spaces are absent in sclerenchymatous tissues. (c) We get a crunchy and granular feeling, when we chew pear fruit.
(d) Branches of a tree move and bend freely in high wind velocity.
(e) It is difficult to pull out the husk of a coconut tree.


Solution

(a) As the cells of the meristematic tissue are very active and no need for storage, they have dense cytoplasm, thin cellulose walls, and prominent nuclei. They lack vacuoles.
(b)The cells of the sclerenchymatous tissue are dead. They are long and narrow as the walls are thickened due to lignin (a chemical substance which acts as cement and hardens them). Since they are lignified there is no internal space inside the cell.

(c) Presence of stone cells (sclerenchyma)
(d) The flexibility in plants is due to a permanent tissue, collenchyma. It allows easy bending in various parts of a plant (leaf, stem) without breaking. It also provides mechanical support to plants.
(e) The husk of a coconut is made of sclerenchymatous tissue. They are lignified and make it difficult to pull.

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