Bihar Board - Class 11 biology - Chapter 6: Anatomy of flowering plants Handwritten Notes

The anatomy of flowering plants focuses on the internal structure of plants and how the arrangement of cells, tissues, and organs contributes to their growth, development, and function. This chapter provides an overview of the various tissues and their organization within the plant body, highlighting how they perform vital roles in plant life processes like nutrient transport, support, and reproduction.

Key Points

1. Plant Tissue System
   The plant body is organized into three primary tissue systems:

   • Dermal Tissue System: The outermost protective layer of the plant, which includes the epidermis.
     • Epidermis: A single layer of cells that forms the outer boundary of the plant. It protects against water loss, pathogens, and physical damage.
     • Stomata: Pores in the epidermis that allow gas exchange and transpiration.
     • Trichomes: Hair-like structures on the surface that can help with protection or reduce water loss.
   • Ground Tissue System: Involved in photosynthesis, storage, and support.
     • Parenchyma: The most common type of ground tissue, responsible for photosynthesis, storage, and secretion.
     • Collenchyma: Provides flexible support, especially in growing parts of the plant.
     • Sclerenchyma: Provides rigid support with thick, lignified walls, often found in non-growing parts.
   • Vascular Tissue System: Responsible for the transport of water, nutrients, and food.
     • Xylem: Transports water and minerals from roots to other parts of the plant. It consists of vessels, tracheids, and fibers.
     • Phloem: Transports food, primarily in the form of sugars, from leaves to other parts of the plant. It consists of sieve tubes, companion cells, and phloem fibers.

2. Tissues of the Root
   The root system anchors the plant and absorbs water and nutrients from the soil. Key tissues include:

   • Epidermis: Outer layer, often with root hairs for increased surface area.
   • Cortex: The region beneath the epidermis, primarily for storage of food.
   • Endodermis: A layer surrounding the vascular bundle that regulates the flow of water and minerals into the vascular tissue.
   • Vascular Bundle: Includes xylem and phloem arranged in a central cylinder to transport water and nutrients.

3. Tissues of the Stem
   The stem provides structural support and is involved in the transport of nutrients and water. It consists of:

   • Epidermis: Protects the stem surface and contains stomata for gas exchange.
   • Cortex: Located between the epidermis and vascular tissue, serving as a storage site for food and water.
   • Vascular Tissue: Xylem and phloem form vascular bundles arranged in a ring in dicots and scattered in monocots.
   • Cambium: A meristematic tissue responsible for secondary growth, producing additional xylem and phloem cells.

4. Tissues of the Leaf
   The leaf is the primary site for photosynthesis and gas exchange. It consists of:

   • Epidermis: The outer layer, often covered by a waxy cuticle to prevent water loss.
   • Mesophyll: The tissue between the epidermis, containing chloroplasts for photosynthesis. It is divided into two layers:
     • Palisade Parenchyma: A layer of tightly packed cells rich in chloroplasts.
     • Spongy Parenchyma: Loosely arranged cells with air spaces for gas exchange.
   • Veins: Contain vascular tissue (xylem and phloem) that transports water and food.

5. Secondary Growth

   • Occurs in dicot plants and some gymnosperms, where lateral meristems (cambium) produce secondary xylem and phloem. This leads to an increase in the thickness or girth of the plant, contributing to the formation of woody plants.
   • Wood: Mainly composed of secondary xylem and provides structural support.

6. Meristematic Tissues

   • Apical Meristems: Located at the tips of roots and shoots, responsible for primary growth (lengthening).
   • Lateral Meristems: Found in the cambium and cork cambium, responsible for secondary growth (thickening).
   • Intercalary Meristems: Present at the base of leaves and internodes in monocots, responsible for growth in length.

7. Specialized Structures

   • Lenticels: Small pores in the bark that allow gas exchange.
   • Bark: The protective outer covering of woody plants, formed by the activity of the cork cambium.

Conclusion

The anatomy of flowering plants reveals the intricate organization of tissues that enable the plant to perform essential functions like growth, nutrient transport, photosynthesis, and reproduction. Understanding plant anatomy is vital for agriculture, horticulture, and plant biology as it provides insights into how plants adapt to their environment, maintain their health, and develop specialized structures for survival.

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