Anatomy of Flowering Plants

Anatomy of flowering plants explores the internal structure and organization of various plant organs. This chapter delves into the different tissues and cell types that make up a plant, as well as their functions.

Plant Tissues:

• Meristematic Tissue: Found in areas of active cell division, responsible for plant growth.
  • Apical meristem: Located at the tips of roots and stems, promoting primary growth.
  • Lateral meristem: Found in the stems and roots of dicotyledonous plants, responsible for secondary growth (thickening).
  • Intercalary meristem: Found in the internodes of grasses and bamboo, promoting growth in length.
• Permanent Tissue: Mature tissues with specialized functions.
  • Simple Tissues: Composed of cells of the same type.
    • Parenchyma: Thin-walled cells with various functions (e.g., storage, photosynthesis).
    • Collenchyma: Thick-walled cells providing mechanical support.
    • Sclerenchyma: Thick-walled cells with lignified walls, providing strength and support.

Plant Organs:

• Root: Anchors the plant and absorbs water and minerals.
• Leaf: The main organ of photosynthesis, containing chlorophyll.
• Flower: The reproductive organ of a plant, consisting of petals, sepals, stamens, and carpels.
• Fruit: The ripened ovary, containing seeds.
• Seed: The reproductive unit of a plant, containing the embryo and endosperm.

Key Points:

• The anatomy of flowering plants is adapted to their specific functions and environments.
• Understanding plant anatomy is essential for understanding plant growth, development, and physiology.
• The study of plant anatomy has applications in agriculture, horticulture, and plant conservation.

Exercise

1. Draw illustrations to bring out the anatomical difference between 

(a) Monocot root and Dicot root (b) Monocot stem and Dicot stem

Ans : 

(a) Monocot root and Dicot root 

(b) Monocot stem and Dicot stem

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

Ans : In dicot stems, vascular bundles are arranged in a ring, while in monocot stems, they are scattered throughout the ground tissue. The arrangement of vascular bundles helps determine whether a young stem is dicot or monocot. Additionally, other distinguishing characteristics of monocot stems include undifferentiated ground tissue, a sclerenchymatous hypodermis, and oval or circular vascular bundles with Y-shaped xylem.

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?

Ans : The plant material you’re describing is most likely a monocot stem

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

Ans : 

The stomatal apparatus is a specialized structure found on the epidermis of plant leaves, primarily responsible for regulating the processes of transpiration and gas exchange. It consists of three main components:

1. Stomatal Pore: This is a small, elliptical opening that allows for the exchange of gases between the plant’s internal tissues and the external environment.
2. Guard Cells: These are specialized epidermal cells that flank the stomatal pore and control its opening and closing. Guard cells are typically bean-shaped in dicots and dumbbell-shaped in monocots. They contain chloroplasts and have thicker inner walls than outer walls.
3. Subsidiary Cells: These are specialized epidermal cells that surround the guard cells. Their number and arrangement vary among different plant species.

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

Ans : 

Ground Tissue System:

• Parenchyma
• Collenchyma
• Sclerenchyma

Vascular Tissue System:

• Xylem
• Phloem

Epidermal Tissue System:

• Epidermis
• Stomata
• Guard Cells
• Trichomes (hairs)

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

Ans : The study of plant anatomy is important for plant identification, agriculture, forestry, medicine, and understanding plant evolution. It helps understand plant structure, growth, and development.

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

Ans : 

Dorsiventral leaves are characteristic of dicotyledonous plants and have distinct upper (adaxial) and lower (abaxial) surfaces. Their internal structure consists of three main layers:

1. Epidermis:

• Outermost layer, both on the upper and lower surfaces.
• Covered with a thick cuticle to prevent water loss.
• Contains stomata (pores) for gas exchange, usually found more abundantly on the lower surface.
• May have trichomes (hairs) for various functions like protection and reducing water loss.

2. Mesophyll:

• Middle layer, composed of parenchyma cells.
• Divided into two distinct zones:
  • Palisade Parenchyma:
    • Upper layer, consisting of elongated, cylindrical cells.
    • Contains numerous chloroplasts for photosynthesis.
  • Spongy Parenchyma:
    • Lower layer, composed of irregularly shaped cells with large intercellular spaces.
    • Facilitates gas exchange and diffusion of carbon dioxide and oxygen.

3. Vascular Bundles (Veins):

• Bundles of xylem and phloem tissues, surrounded by bundle sheath cells.
• Phloem conducts food (sugars) from leaves to other parts of the plant.
• Vascular bundles are typically arranged in a reticulate (net-like) pattern.