Q. 525.0( 8 Votes )
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.
a) Meristematic cells are continuously dividing cells of the plant body. Division is facilitated by nucleus and cytoplasm; but they lack vacuoles because vacuoles are used for storage in plants and meristematic tissues do not require vacuole.
b) Sclerenchymatous tissues are dead simple permanent tissues of the plant, made of lignified cell walls. They have no intercellular spaces because they function to provide strength and elasticity to the plant.
c) We get a crunchy and granular feeling, when we chew pear fruit because they are made of sclerenchyma tissue whose cell walls are lignified.
d) Branches of a tree move and bend freely in high wind velocity due to the deposition of collenchyma cells which have cellulose at the corners of tissue. Collenchyma is a mechanical tissue that provides elasticity and support to the branches. Therefore, the branches move and bend freely in high wind velocity.
e) It is difficult to pull out the husk of a coconut tree as they are made of sclerenchyma tissue. The cells of sclerenchyma tissues are closely packed without intercellular spaces. A thin layer of connecting substances that contains pectin, lignin and protein exists between them, known as middle lamellae.
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