Chapter 6 : Anatomy of Flowering Plants

Class 11 Biology Chapter 6 Anatomy of Flowering Plants Exercise Questions and Answers :

1. Draw illustrations to bring out the anatomical difference between

(a) Monocot root and Dicot root

(b) Monocot stem and Dicot stem .

Answer : (a) The anatomical difference between Monocot Root and Dicot Root :

Monocot Root :

     

(i) Vascular bundles are scattered and are not arranged in a specific pattern.

(ii) The cortex is usually parenchymatous and lacks a well-defined endodermis.

(iii) Typically lacks a pith in the center.

Dicot Root :

 

(i) Vascular bundles are arranged in a distinct central pattern in the shape of a cross .

(ii) The cortex may contain sclerenchyma and often has a distinct endodermis layer.

(iii)  Often contains a central pith in the root.

(b) The anatomical difference between Monocot Stem and Dicot Stem :

Monocot Stem :

(i) Vascular bundles are scattered throughout the stem.

(ii) Ground tissue usually lacks a clear distinction between cortex and pith.

(iii) Lacks a vascular cambium for secondary growth.

Dicot Stem :

(i) Vascular bundles are arranged in a distinct ring or cylinder.

(ii) Ground tissue is divided into cortex and pith, with pith in the center.

 (iii) Contains a vascular cambium, allowing for secondary growth and increased stem thickness.

2. Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem? Give reasons.

Answer :  To ascertain whether the transverse section of a young stem from our school garden is from a monocot or a dicot plant, we can follow these steps and look for specific features under a microscope :

1. Examine the Arrangement of Vascular Bundles :

Monocot Stem: In monocot stems, the vascular bundles are scattered throughout the stem without a specific arrangement. They are typically numerous and appear as small, discrete bundles.

Dicot Stem: In dicot stems, the vascular bundles are arranged in a distinct ring or cylinder just beneath the epidermis. These bundles are fewer in number but larger and more organized.

2. Observe the Presence of Pith :

Monocot Stem: Monocot stems usually lack a pith in the center. Instead, they have ground tissue without a central core.

Dicot Stem: Dicot stems often contain a pith in the center, a central region of parenchyma tissue.

3. Look for the Presence of Vascular Cambium:

Monocot Stem: Monocot stems lack a vascular cambium, which is responsible for secondary growth in dicot stems.

Dicot Stem: Dicot stems contain a vascular cambium, which allows for secondary growth and an increase in stem thickness over time.

By observing these features in the transverse section under a microscope, you can determine whether the stem belongs to a monocot or a dicot plant. If you see scattered vascular bundles, the absence of a pith, and no vascular cambium, it is likely a monocot stem. On the other hand, if you observe an organized ring of vascular bundles, the presence of a pith, and a vascular cambium, it is likely a dicot stem.

3. The transverse section of a plant material shows the following anatomical features - (a) the vascular bundles are conjoint, scattered and surrounded by a sclerenchymatous bundle sheaths. (b) phloem parenchyma is absent. What will you identify it as?

Answer : Based on the provided anatomical features in the transverse section of the plant material:

(a) Vascular bundles are conjoint, scattered, and surrounded by a sclerenchymatous bundle sheath.

(b) Phloem parenchyma is absent.

These characteristics indicate that the plant material is likely a monocot stem. In monocot stems, vascular bundles are typically conjoint (xylem and phloem are together), scattered throughout the stem, and are often surrounded by a bundle sheath of sclerenchyma. Additionally, monocot stems commonly lack phloem parenchyma, which distinguishes them from dicot stems where phloem parenchyma is usually present.

4. What is stomatal apparatus? Explain the structure of stomata with a labeled diagram.

Answer : The stomatal apparatus is a vital structure in the epidermis of leaves that regulates transpiration and gaseous exchange. Each stomatal apparatus consists of two bean-shaped guard cells enclosing a stomatal pore. In grasses, guard cells are dumb-bell shaped. The outer walls of guard cells are thin, and the inner walls are thickened. Guard cells contain chloroplasts and control stomatal opening and closing. Sometimes, specialized subsidiary cells are found near guard cells. Together, the stomatal aperture, guard cells, and subsidiary cells form the stomatal apparatus. It plays a crucial role in plant gas exchange and transpiration regulation.

             (a)                                                          (b)

(a) stomata with bean-shaped guard cells
(b) stomata with dumb-bell shaped guard cell

5. Name the three basic tissue systems in the flowering plants. Give the tissue names under each system.

Answer :  The three basic tissue systems in flowering plants are:

Dermal Tissue System :

(i) Epidermal Tissue   

(ii) Periderm (in woody plants)

Vascular Tissue System :

(i) Xylem Tissue

(ii) Phloem Tissue

Ground Tissue System :

(i) Parenchyma Tissue

(ii) Collenchyma Tissue

(iii) Sclerenchyma Tissue

(iv) Mesenchymal Tissue (in some plants)

6. How is the study of plant anatomy useful to us?

Answer : The study of plant anatomy is useful to us because:

(i) It helps in understanding the internal structure of plants, including different types of tissues and their functions.

(ii) It aids in identifying and characterizing plant structures that play vital roles in food assimilation, storage, water transportation, and mechanical support.

(iii) It allows for the classification of tissues into meristematic and permanent categories.

(iv) It provides insights into the organization of the three tissue systems: epidermal, ground, and vascular.

(v) It helps in recognizing variations in the internal structures between monocotyledonous and dicotyledonous plants.

(vi) It is essential for comprehending processes like secondary growth, which occurs in most dicotyledonous roots and stems.

Overall, plant anatomy contributes to our knowledge of how plants function, grow, and adapt, benefiting fields such as agriculture, botany, and environmental science.

7. Describe the internal structure of a dorsiventral leaf with the help of labeled diagrams.

Answer : The internal structure of a dorsiventral leaf can be described as follows:

(a) Epidermis:

(i) The leaf has two epidermal layers, the upper surface (adaxial epidermis) and the lower surface (abaxial epidermis), both covered with a conspicuous cuticle.

(ii) The abaxial epidermis typically has more stomata than the adaxial epidermis, which may even lack stomata.

(b). Mesophyll:

(i) The mesophyll is the tissue between the upper and lower epidermis responsible for photosynthesis.

(ii) It consists of two types of parenchyma cells: palisade parenchyma and spongy parenchyma.

(iii) The adaxially placed palisade parenchyma consists of elongated cells arranged vertically and parallel to each other.

(iv) The spongy parenchyma, situated below the palisade cells and extending to the lower epidermis, contains oval or round, loosely arranged cells with numerous air cavities between them.

(c) Vascular System:

(i) The vascular system includes vascular bundles found in the veins and midrib of the leaf.

(ii) The size of the vascular bundles depends on the size of the veins.

(iii) In the reticulate venation of dicot leaves, the veins vary in thickness.

(iv) The vascular bundles are surrounded by a layer of thick-walled bundle sheath cells, providing structural support.

Diagram of  T.S. of Dorsiventral (Dicotyledonous) Leaf