Morphology of Flowering Plants – Class 11 Biology Notes
Introduction to Morphology of Flowering Plants
Morphology refers to the study of the external structure and form of plants. Flowering plants, also called angiosperms, exhibit a variety of structures, each of which serves a specific function in growth, reproduction, and survival. In this chapter, we will study the different plant parts — roots, stems, leaves, flowers, and fruits — and their modifications.
1. Root
Functions of Roots:
- Anchorage: Roots anchor the plant to the soil.
- Absorption: Roots absorb water and minerals from the soil.
- Storage: Some roots store food and water (e.g., carrots, beetroot).
- Conduction: Roots transport absorbed water and nutrients to other parts of the plant.
Types of Roots:
- Tap Root System:
- The primary root grows thick and deep.
- Found in dicots like mustard, bean, and sunflower.
- Example: Carrot, radish.
- Fibrous Root System:
- A large number of thin roots arise from the base of the stem.
- Found in monocots like wheat, rice, and grass.
- Example: Onion, grass.
Modification of Roots:
- Tuberous Roots: Swollen roots that store food (e.g., sweet potato).
- Fleshy Roots: Store water and nutrients (e.g., carrot).
- Pneumatophores: Specialized roots for breathing in waterlogged conditions (e.g., mangrove trees).
- Prop Roots: Roots that arise from the stem and provide extra support (e.g., banyan tree).
2. Stem
Functions of Stems:
- Support: Supports branches, leaves, and flowers.
- Conduction: Transports water, nutrients, and food between roots and leaves.
- Storage: Stores food and water in some plants (e.g., in potato tubers).
- Photosynthesis: In some plants, the stem is capable of photosynthesis (e.g., cactus).
Types of Stems:
- Aerial Stems:
- Grow above the ground and support leaves and flowers.
- Examples: Herbaceous plants, shrubs, trees.
- Underground Stems:
- Grow beneath the soil and help in vegetative reproduction.
- Examples: Potato (tuber), ginger (rhizome), onion (bulb).
- Subaerial Stems:
- Stems partially above the ground but also have underground parts.
- Examples: Strawberry (runner), mint (stolon).
Modification of Stems:
- Tendrils: Help in climbing (e.g., pea plant).
- Thorns: Protect the plant (e.g., rose).
- Cladodes: Flattened stem that carries out photosynthesis (e.g., cactus).
- Rhizomes: Underground stems for vegetative reproduction (e.g., ginger).
- Bulbs: Modified stems with food storage (e.g., onion).
3. Leaves
Functions of Leaves:
- Photosynthesis: Main site for food production in the plant.
- Transpiration: Loss of water vapor from the plant through stomata.
- Storage: Some leaves store food and water (e.g., aloe vera).
Parts of a Leaf:
- Petiole: Stalk that attaches the leaf to the stem.
- Lamina (Leaf Blade): Flat part of the leaf that performs photosynthesis.
- Midrib: The central vein of the leaf.
- Veins: Vascular tissues that transport water, minerals, and nutrients.
Types of Leaves:
- Simple Leaf: Single leaf blade attached to the petiole.
- Examples: Mango, hibiscus.
- Compound Leaf: Leaf divided into leaflets.
- Examples: Neem, rose.
Modification of Leaves:
- Spines: Modified leaves for protection (e.g., cactus).
- Tendrils: Modified leaves that help the plant climb (e.g., pea).
- Scale Leaves: Protect buds (e.g., in onions).
- Storage Leaves: Store water and food (e.g., onion, aloe vera).
4. Flowers
Parts of a Flower:
- Reproductive Organs:
- Stamens (Male Part): Produce pollen grains.
- Carpels (Female Part): Produce ovules and form the fruit.
- Non-reproductive Parts:
- Sepals: Protect the flower bud.
- Petals: Attract pollinators.
Flower Types:
- Complete Flower: Contains all four whorls (calyx, corolla, androecium, and gynoecium).
- Example: Rose, hibiscus.
- Incomplete Flower: Lacks one or more whorls.
- Example: Corn, cucumber.
- Unisexual Flower: Contains either stamens or carpels.
- Example: Papaya, cucumber.
- Bisexual Flower: Contains both stamens and carpels.
- Example: Lily, rose.
Inflorescence:
- Definition: Arrangement of flowers on the plant.
- Types of Inflorescence:
- Racemosa: Flowers arranged in a simple cluster (e.g., mustard).
- Cymose: Flowers arranged in a branched manner (e.g., jasmine).
5. Fruits
Types of Fruits:
- Simple Fruits: Develop from a single ovary of a single flower.
- Examples: Mango, pea.
- Aggregate Fruits: Develop from multiple ovaries of a single flower.
- Examples: Strawberry, raspberry.
- Multiple Fruits: Develop from the ovaries of multiple flowers.
- Examples: Pineapple, fig.
Parts of a Fruit:
- Pericarp (Fruit Wall): Forms from the ovary wall.
- Exocarp: Outer layer (skin).
- Mesocarp: Middle layer (flesh).
- Endocarp: Inner layer (around the seed).
MCQs – Morphology of Flowering Plants
1. The part of a flower that attracts pollinators is:
a) Sepal
b) Petal
c) Stamen
d) Carpel
Answer: b) Petal
2. The primary function of roots is:
a) Photosynthesis
b) Storage of food
c) Absorption of water and minerals
d) Protection
Answer: c) Absorption of water and minerals
3. Which of the following is a modification of a stem?
a) Tuber
b) Tendril
c) Spine
d) None of the above
Answer: a) Tuber
4. A leaf with leaflets arranged on both sides of the axis is:
a) Pinnately compound leaf
b) Palmately compound leaf
c) Simple leaf
d) None of the above
Answer: a) Pinnately compound leaf
5. The edible part of a banana is:
a) Root
b) Stem
c) Fruit
d) Leaf
Answer: c) Fruit
6. Which of the following is an example of a monocot plant?
a) Mango
b) Wheat
c) Sunflower
d) Rose
Answer: b) Wheat
7. The modified leaf of a cactus for water storage is:
a) Tendril
b) Spine
c) Scale leaf
d) Leaf blade
Answer: b) Spine
8. Which of the following is not a function of the stem?
a) Support for leaves
b) Storage of food
c) Photosynthesis
d) Absorption of water
Answer: d) Absorption of water
9. Which part of the flower develops into fruit?
a) Ovary
b) Stigma
c) Style
d) Anther
Answer: a) Ovary
10. A leaf with a single leaf blade and no leaflets is:
a) Simple leaf
b) Compound leaf
c) Pinnate leaf
d) Both a and b
Answer: a) Simple leaf