NEET Biology Anatomy of Flowering Plants MCQs Set 03

Answer: (c) Divide continuously to give rise to new cells

Explanation:
1. Meristematic cells are young, thin-walled, with dense cytoplasm and keep dividing.
2. Cells that stop dividing and elongate become permanent tissues.

Teacher's Note:
1. Meristems are the growth centres of plants. Their cells are small and have no large vacuoles.

Answer: (a) Apical meristem

Explanation:
1. The root and shoot apices contain histogens, which are the layers that give rise to the epidermis, cortex and stele (dermatogen, periblem and plerome).
2. These layers are not found in intercalary or lateral meristems.

Teacher's Note:
1. Histogen theory was proposed by Hanstein. Dermatogen forms the epidermis, periblem the cortex and plerome the stele.

Answer: (b) Pistia

Explanation:
1. Pistia is a floating hydrophyte, in which the root cap is replaced by a root pocket.
2. Hollyhock, sunflower and China rose are terrestrial dicots with normal root caps.

Teacher's Note:
1. Root pockets protect the roots of aquatic plants such as Pistia and Eichhornia.

Answer: (d) 4

Explanation:
1. Monocot root apex has four histogens: dermatogen, periblem, plerome, and a separate calyptrogen that forms the root cap.
2. In dicots the root cap arises from dermatogen, so three histogens are recognised.

Teacher's Note:
1. Remember: monocot root = 4 histogens (with calyptrogen), dicot root = 3.

Answer: (c) Primary permanent tissue

Explanation:
1. Secondary meristems such as the cork cambium form by dedifferentiation of permanent (mature) tissue.
2. Promeristem and primary meristem are original meristems.

Teacher's Note:
1. Cork cambium and interfascicular cambium are secondary meristems.

Answer: (a) To provide protection to the root apex

Explanation:
1. The thimble-like root cap covers the apical meristem and protects it from injury as the root pushes through the soil.
2. It secretes mucilage that eases the passage of the root.

Teacher's Note:
1. Root hairs absorb water; the root cap only protects.

Answer: (b) Low

Explanation:
1. The cells of the quiescent centre divide very rarely and have a low DNA content and low metabolic activity.
2. They act as a reserve that replaces damaged cells.

Teacher's Note:
1. Quiescent centre theory was proposed by Clowes.

Answer: (d) Marginal meristem

Explanation:
1. Marginal meristem along the leaf margin gives rise to the lamina.
2. Apical meristems occur at root and shoot tips.

Teacher's Note:
1. Based on position meristems are apical, intercalary and lateral.

Answer: (a) Chlorophyll containing parenchyma

Explanation:
1. Chlorenchyma is parenchyma that has chloroplasts and is mainly photosynthetic.
2. It is present in leaves and young stems.

Teacher's Note:
1. Aerenchyma is parenchyma with large air spaces. Chlorenchyma carries out photosynthesis.

Answer: (a) Providing buoyancy to hydrophytes

Explanation:
1. Large air cavities in aerenchyma make aquatic plants float and help gas exchange.
2. Mechanical strength comes from collenchyma and sclerenchyma.

Teacher's Note:
1. Aerenchyma is typical of hydrophytes such as Hydrilla and lotus.

Answer: (b) Meristem

Explanation:
1. Meristematic cells are living and actively dividing.
2. Vessels, cork cells and fibres are dead at maturity.

Teacher's Note:
1. Dead tissues include tracheids, vessels, fibres and cork. Xylem parenchyma is the living part of xylem.

Answer: (a) Parenchyma

Explanation:
1. Parenchyma cells are thin walled and store food, so they make up potato tuber, fruit pulp and the cortex.
2. Collenchyma and sclerenchyma are mechanical tissues.

Teacher's Note:
1. Parenchyma is the most abundant tissue and forms the ground tissue.

Answer: (b) Collenchyma

Explanation:
1. Collenchyma has living cells with unevenly thickened corners and gives support to young organs.
2. Sclerenchyma is dead.

Teacher's Note:
1. Collenchyma is absent in monocots and roots.

Answer: (a) Retaining protoplasm at maturity

Explanation:
1. Collenchyma cells are living at maturity, whereas sclerenchyma cells are dead and lose their protoplasm.
2. Both have thickened walls and neither is meristematic.

Teacher's Note:
1. Collenchyma has cellulose, hemicellulose and pectin thickenings; sclerenchyma is lignified.

Answer: (b) Collenchyma

Explanation:
1. Collenchyma lies below the epidermis in dicot stems and offers flexible mechanical support to growing parts.
2. Sclerenchyma is rigid and found in mature parts.

Teacher's Note:
1. Young growing organs need flexible support, which collenchyma gives.

Answer: (d) All of the above

Explanation:
1. Collenchyma is absent in monocots and in roots.
2. It is found only in the hypodermis of dicot stems and leaves.

Teacher's Note:
1. Collenchyma is a dicot stem and leaf tissue.

Answer: (c) Lignin

Explanation:
1. Sclerenchyma cell walls are heavily thickened with lignin, which makes the cells hard and dead.
2. Collenchyma has cellulose and pectin.

Teacher's Note:
1. Lignin is a waterproof, strengthening polymer.

Answer: (b) Xylem vessels

Explanation:
1. Mature xylem vessels have lost their protoplasm and are dead tubes.
2. Cambium cells, root hairs and companion cells are living.

Teacher's Note:
1. Vessels are efficient water conduits because they are hollow.

Answer: (d) Gymnosperms

Explanation:
1. Gymnosperms have tracheids as the main water-conducting cells and have abundant bordered pits.
2. Angiosperms depend more on vessels.

Teacher's Note:
1. Gymnosperm wood has no vessels, so it is non-porous.

Answer: (c) Companion cell

Explanation:
1. Companion cells are living cells connected to sieve tube elements by plasmodesmata.
2. They supply energy and help loading of sugars.

Teacher's Note:
1. Sieve tube and companion cell arise from the same mother cell.