Important questions based on NCERT syllabus for Chapter 6 - Tissues:
Question-1: Define meristematic tissue. Why do meristematic cells lack vacuoles?
Solution: Meristematic tissues are cells or group of cells that have the ability to divide. These tissues in a plant consist of small, densely packed cells that can keep dividing to form new cells.
The purpose of vacuole is to store food and waste product. Since meristems are young cells and are actively dividing, they do not participate actively in food preparation. Also, they do not produce large amount of waste. Hence, they lack vacuoles.
Question-2: Give reasons for the following :
(a) Aquatic plants can float on water.
(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.
Solution: (a) Aquatic plants have large air cavities in their parenchyma to give buoyancy to plants which help them float.
(b) The cells of sclerenchymatous tissue 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 intercellular space between the cell.
(c) We get a crunchy and granular feeling when we chew pear fruit. It is due to the 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.
Question-3: List some characteristics of the meristematic tissues.
Solution: The characteristics of meristematic tissues are as follows:
i. They are actively dividing cells and they divide throughout their life.
ii. Cells are compactly arranged with no intercellular spaces.
iii. Cells lack vacuoles.
iv. Cells have dense cytoplasm.
v. Cells have a prominent nucleus.
vi. Cells have thin cell walls.