Biology Class 11 NCERT Solutions: Chapter 6 Anatomy of Flowering Plants Part 3

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Q: 6. The transverse section of a plant material shows the following anatomical features,

(A) The vascular bundles are conjoint, scattered and surrounded by sclerenchymatous bundle sheaths (b) phloem parenchyma is absent. What will you identify it as?

Answer

The monocot stem is characterised by conjoint, collateral, and closed vascular bundles, scattered in the ground tissue containing the parenchyma. Each vascular bundle is surrounded by sclerenchymatous bundle-sheath cells. Phloem parenchyma and medullary rays are absent in monocot stems.

Q: 7. Why are xylem and phloem called complex tissues?

Answer:

Image shows the xylem and phloem

Image Shows the Xylem and Phloem

Image shows the xylem and phloem

Xylem and phloem are known as complex tissues as they are made up of more than one type of cells. These cells work in a coordinated manner, as a unit, to perform the various functions of the xylem and phloem.

Image shows the complex tissues

Image Shows the Complex Tissues

Image shows the complex tissues

Xylem helps in conducting water and minerals. It also provides mechanical support to plants. It is made up of the following components:

Tracheid’s (xylem vessels and xylem tracheid’s)

Xylem Parenchyma

Xylem Fibres

Tracheids are elongated, thick-walled dead cells with tapering ends. Vessels are long, tubular, and cylindrical structures formed from the vessel members, with each having lignified walls and large central cavities. Both tracheid’s and vessels lack protoplasm. Xylem fibres consist of thick walls with an almost insignificant lumen. They help in providing mechanical support to the plant. Xylem parenchyma is made up of thin-walled parenchymatous cells that help in the storage of food materials and in the radial conduction of water.

Phloem helps in conducting food materials. It is composed of:

Sieve tube elements

Companion cells

Phloem Parenchyma

Phloem Fibres

Sieve tube elements are tube-like elongated structures associated with companion cells. The end walls of sieve tube elements are perforated to form the sieve plate. Sieve tube elements are living cells containing cytoplasm and nucleus. Companion cells are parenchymatous in nature. They help in maintaining the pressure gradient in the sieve tube elements. Phloem parenchyma helps in the storage of food and is made up of long tapering cells, with a dense cytoplasm. Phloem fibres are made up of elongated sclerenchymatous cells with thick cell walls.

Q: 8. What is stomatal apparatus? Explain the structure of stomata with a labelled diagram.

Answer

Stomata are small pores present in the epidermis of leaves. They regulate the process of transpiration and gaseous exchange. The stomatal pore is enclosed between two bean-shaped guard cells. The inner walls of guard cells are thick, while the outer walls are thin. The guard cells are surrounded by subsidiary cells. These are the specialised epidermal cells present around the guard cells. The pores, the guard cells, and the subsidiary cells together constitute the stomatal apparatus.

Q 8 Image of Stomata with Labelled Diagram

Q 8 Image of Stomata With Labelled Diagram

Q 8 Image of Stomata with Labelled Diagram

Q: 9. Name the three basic tissue systems in the flowering plants. Give the tissue names under each system.

Answer:

Tissues in Tissue Systems
Tissues in tissue systems

No.

Tissue System

Tissues Present

1.

Epidermal tissue System

Epidermis, trichomes, hairs, stomata

2.

Ground Tissue System

Parenchyma, Collenchyma, Sclerenchyma , Mesophyll

3.

Vascular Tissue System

Xylem, Phloem, Cambium

Q: 10. How is the study of plant anatomy useful to us?

Answer:

The study of plant anatomy helps us to understand the structural adaptations of plants with respect to diverse environmental conditions. It also helps us to distinguish between monocots, dicots, and gymnosperms. Such a study is linked to plant physiology. Hence, it helps in the improvement of food crops. The study of plant-structure allows us to predict the strength of wood. This is useful in utilising it to its potential. The study of various plant fibres such as jute, flax, etc., helps in their commercial exploitation.

Q: 11. What is periderm? How does periderm formation take place in dicot stem?

Answer

Periderm is composed of the phellogen, phellem, and phelloderm. During secondary growth, the outer epidermal layer and the cortical layer are broken because of the cambium. To replace them, the cells of the cortex turn meristematic, giving rise to cork cambium or phellogen. It is composed of thin-walled, narrow and rectangular cells. Phellogen cuts off cells on its either side. The cells cut off toward the outside give rise to the phellem or cork. The suberin deposits in its cell wall make it impervious to water. The inner cells give rise to the secondary cortex or phelloderm. The secondary cortex is parenchymatous.

Image of the formation of periderm

Image of the Formation of Periderm

Image of the formation of periderm