Morphology is the branch of biology that deals with the form and structure of organisms. In the context of flowering plants (angiosperms), morphology helps us understand the external features of plants which are crucial for identification, classification, and studying the relationship between different plants.
Root
Types of Roots
1. Tap Root System:
- Found in dicots.
- Consists of a primary root (tap root) that grows directly downward and gives rise to lateral roots.
- Example: Carrot, Radish.
2. Fibrous Root System:
- Found in monocots.
- Consists of numerous thin, fibrous roots that grow from the base of the stem.
- Example: Grass, Wheat.
3. Adventitious Root System:
- Roots that develop from parts of the plant other than the radicle.
- Example: Banyan tree (prop roots), Maize (stilt roots).
Modifications of Roots:
Roots may be modified for various functions like storage, support, and respiration.
1. Storage Roots:
- Swollen roots that store food.
- Example: Carrot, Sweet Potato.
2. Prop Roots:
- Arise from the branches and descend downwards to provide support.
- Example: Banyan tree.
3. Pneumatophores:
- Also known as respiratory roots, they grow upwards and help in gaseous exchange.
- Example: Mangrove plants.
Stem
Structure and Functions
The stem is the ascending part of the plant axis that bears branches, leaves, flowers, and fruits. It conducts water, minerals, and food to different parts of the plant.
Modifications of Stems:
Stems may be modified to perform various functions such as storage, support, and vegetative propagation.
1. Tuber:
- Swollen, underground stem that stores food.
- Example: Potato.
2. Rhizome:
- Horizontal, underground stem that stores food and helps in vegetative propagation.
- Example: Ginger, Turmeric.
3. Bulb:
- Shortened, underground stem with fleshy leaves storing food.
- Example: Onion, Garlic.
4. Runner:
- Horizontal stem that grows above ground and helps in vegetative propagation.
- Example: Strawberry.
5. Cladodes:
- Green, flattened stems that perform photosynthesis.
- Example: Asparagus.
Leaf:
Structure:
A typical leaf consists of three parts:
Leaf Base: The part that attaches the leaf to the stem.
Petiole: The stalk that connects the leaf blade to the stem.
Lamina (Leaf Blade): The flat, green part of the leaf where photosynthesis occurs.
Venation:
Venation is the arrangement of veins in a leaf. It can be:
1. Reticulate Venation:
- Veins form a network.
- Common in dicots.
- Example: Mango, Hibiscus.
2. Parallel Venation:
- Veins run parallel to each other.
- Common in monocots.
- Example: Grass, Banana.
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Modifications of Leaves
Leaves may be modified to perform various functions such as support, storage, and protection.
1. Tendrils:
- Leaves or parts of leaves modified into slender, coiling structures for support.
- Example: Pea.
2. Spines:
- Leaves or parts of leaves modified into sharp structures for protection.
- Example: Cactus.
3. Succulent Leaves:
- Thick, fleshy leaves that store water.
- Example: Aloe Vera.
4. Insectivorous Leaves:
- Leaves modified to trap and digest insects.
- Example: Pitcher Plant, Venus Flytrap.
Flower
Structure:
A flower is the reproductive part of angiosperms. It typically consists of four whorls:
Calyx: The outermost whorl, consisting of sepals which protect the flower bud.
Corolla: The whorl of petals, often brightly colored to attract pollinators.
Androecium: The male reproductive whorl, consisting of stamens. Each stamen has an anther and a filament.
Gynoecium: The female reproductive whorl, consisting of one or more carpels. Each carpel has an ovary, style, and stigma.
Types of Flowers:
1. Complete Flowers:
- Have all four whorls (calyx, corolla, androecium, gynoecium).
- Example: Hibiscus.
2. Incomplete Flowers:
- Lacking one or more whorls.
- Example: Corn (female flowers lack stamens).
Flower Symmetry:
1. Actinomorphic (Radial Symmetry):
- Can be divided into two equal halves in multiple planes.
- Example: Mustard.
2. Zygomorphic (Bilateral Symmetry):
- Can be divided into two equal halves in only one plane.
- Example: Pea.
Fruit:
Types of Fruits:
1. Simple Fruits:
- Develop from a single ovary.
- Example: Mango, Tomato.
2. Aggregate Fruits:
- Develop from multiple ovaries of a single flower.
- Example: Strawberry, Raspberry.
3. Multiple Fruits:
- Develop from the ovaries of multiple flowers.
- Example: Pineapple, Mulberry.
Fruit Development:
Fruits develop from the ovary after fertilization. The ovary wall develops into the pericarp, which may be fleshy or dry. The seed(s) develop from the ovules.
Seed:
Structure:
A typical seed consists of:
Seed Coat: The protective outer layer.
Embryo: The young plant, consisting of the radicle (future root), plumule (future shoot), and cotyledons (seed leaves).
Endosperm: The nutritive tissue for the developing embryo (present in some seeds).
Types of Seeds
1. Monocotyledonous Seeds:
- Have one cotyledon.
- Example: Maize, Wheat.
2. Dicotyledonous Seeds:
- Have two cotyledons.
- Example: Pea, Bean.
Seed Germination:
Germination is the process by which a seed develops into a new plant. It requires favorable conditions such as water, oxygen, and a suitable temperature. The radicle emerges first, followed by the plumule.
Summary
Understanding the morphology of flowering plants involves studying their external structures, including roots, stems, leaves, flowers, fruits, and seeds. Each part has unique adaptations and modifications that help the plant survive, reproduce, and thrive in its environment. This knowledge is fundamental for plant identification, classification, and understanding the intricate relationships within the plant kingdom.
These notes provide a comprehensive overview of the morphology of flowering plants and should be useful for Class 11 Biology students. If you need any additional details or specific topics covered, feel free to ask!