Question

Give reasons for
(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuoles.
(b) Intercellular spaces are absent in sclerencymatous tissue.
(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 coconut.

Answer 1

(a) Meristematic cells are actively dividing cells. For a cell to divide, its volume: surface area ratio should be high. This triggers the process of cell division. As meristematic cells need to divide at rapid rate, they have dense cytoplasm and large nucleus. The role of the vacuoles in the cell is to store ergastic substances. Since meristematic cells are rapidly dividing cells, they do not have the need for storage. Hence, meristematic cells have no vacuoles.

(b) Sclerenchyma is made up of long, narrow, and thick-walled cells. The walls of these cells are thick because of the deposition of a chemical substance called lignin. Also, the cells with thick walls are arranged very tightly with no intercellular spaces. These factors make sclerenchyma a hard tissue. It is responsible for providing mechanical strength to plants.

(c) We get a crunchy and granular feeling when we chew pear fruit due to the presence of sclereids. Sclereids are sclerenchymatous cells which are short and have thick lignified walls. They may vary greatly in their size and shape.

(d) Branches of a tree move and bend freely in high wind velocity due to the presence of collenchyma tissue. This tissue provides flexiblity to the branches.

(e) Husk of coconut is made up of sclerenchyma and the sclerenchymatous fibers are closely packed. This makes it difficult to pull them apart.