51. Give reasons for : (i) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole. (ii) Intercellular spaces are absent in sclerenchymatous tissues. (iii) We get a crunchy and granular feeling, when we chew pear fruit. (iv) Branches of a tree move and bend freely in high wind velocity. (v) It is difficult to pull out the husk of a coconut tree.

(i) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole because the meristimatic cell undergoes cell division and have no requirement to store food. (ii) Intercellular spaces are absent in sclerenchymatous tissues because the walls have lignin deposition which provides mechanical strength. (iii) We get a crunchy and granular feeling, when we chew pear fruit because the fruit contains stone cells commonly known as sclereids (sclerenchyma). (iv) Branches of a tree move and bend freely in high wind velocity because the presence of collenchyma adds the property of flexibility. (v) It is difficult to pull out the husk of a coconut tree because it is composed of sclerenchyma fibres which are very closely packed.