Morphology of Flowering Plants Notes: Class 11 Biology Chapter 5
Class 11 Biology Chapter 5 Morphology of Flowering Plants covers the structural features of flowering plants, including root, stem, leaf, inflorescence, flower, fruit, seed, and family descriptions (Solanaceae, Fabaceae, Liliaceae).
Overview of Topics & Subtopics (Click to Jump)
1. The Root System & Modifications
Short Note:
• Types of Root Systems:
- Tap Root System: Primary root develops directly from radicle (e.g., Mustard, Dicot plants).
- Fibrous Root System: Primary root is short-lived, replaced by a large number of roots originating from base of stem (e.g., Wheat, Monocot plants).
- Adventitious Roots: Roots arising from parts of the plant other than radicle (e.g., Grass, Banyan tree, Monstera).
• Regions of Root: Root Cap (protection) → Region of Meristematic Activity (rapid cell division) → Region of Elongation (length expansion) → Region of Maturation (bears fine root hairs for water/mineral absorption).
• Root Modifications: Storage (Carrot, Turnip, Sweet potato), Support (Prop roots in Banyan, Stilt roots in Maize/Sugarcane), Respiration (Pneumatophores in Rhizophora).
2. The Stem & Modifications
Short Note:
• Ascending part of the plant axis developed from the plumule of the embryo. Bears nodes and internodes.
• Stem Modifications:
- Underground Stem Storage: Potato (tuber), Ginger (rhizome), Turmeric, Colocasia, Garlic (bulb).
- Stem Tendrils: Slender, spirally coiled structures for climbing (e.g., Gourd, Cucumber, Watermelon, Grapevines).
- Thorns: Woody, straight, pointed structures for defense against herbivores (e.g., Citrus, Bougainvillea).
- Phylloclade: Flattened (Opuntia) or cylindrical (Euphorbia) green stems carrying out photosynthesis in arid regions.
3. The Leaf
Short Note:
• Lateral, generally flattened vegetative organ originating from shoot apical meristem. Consists of 3 parts: Leaf base, Petiole, and Lamina (leaf blade).
• Venation: Arrangement of veins in lamina. Reticulate venation (network, characteristic of Dicots) vs. Parallel venation (parallel veins, characteristic of Monocots).
• Types of Leaves: Simple Leaf (incision does not touch midrib) vs. Compound Leaf (lamina incision reaches midrib breaking it into leaflets—Pinnately compound e.g. Neem, or Palmately compound e.g. Silk cotton).
• Phyllotaxy: Pattern of leaf arrangement on stem or branch. Alternate (Mustard, China rose), Opposite (Calotropis, Guava), Whorled (Alstonia).
4. Inflorescence & Flower Structure
Short Note:
• Inflorescence: Arrangement of flowers on the floral axis. Racemose (main axis continues to grow, acropetal order) vs. Cymose (main axis terminates in flower, basipetal order).
• Flower Whorls: Calyx (sepals), Corolla (petals), Androecium (stamens), Gynoecium (carpels).
• Position of Ovary: Hypogynous (Superior ovary e.g., Mustard), Perigynous (Half-inferior e.g., Rose, Peach), Epigynous (Inferior ovary e.g., Guava, Cucumber).
• Aestivation: Arrangement of sepals/petals in floral bud. Types: Valvate (Calotropis), Twisted (China rose), Imbricate (Cassia, Gulmohar), Vexillary (Pea, Bean).
• Placentation: Arrangement of ovules within ovary. Types: Marginal (Pea), Axile (Tomato, Lemon), Parietal (Mustard), Free central (Dianthus), Basal (Sunflower, Marigold).
5. Fruit, Seed & Plant Families
Short Note:
• Fruit: Mature or ripened ovary after fertilization. Parthenocarpic fruit develops without fertilization (e.g., Banana). Drupe fruit has thin epicarp, mesocarp, and stony endocarp (e.g., Mango, Coconut).
• Seed: Made up of seed coat and embryo. Dicots contain 2 cotyledons (Gram, Pea); Monocots contain 1 cotyledon with specialized aleurone layer, scutellum, coleoptile, and coleorhiza (e.g., Maize).
• Family Characteristics:
- Fabaceae: Papilionaceous corolla, diadelphous stamens (9+1), marginal placentation, legume fruit.
- Solanaceae: Persistent calyx, epipetalous stamens, swollen placenta with axile placentation, berry or capsule fruit (Potato, Tomato, Brinjal).
- Liliaceae: Monocot family, perianth (tepals 3+3), epiphyllous stamens (3+3), tricarpellary syncarpous ovary (Onion, Aloe).
Intext & Conceptual Questions
Placentation refers to the pattern of arrangement of ovules attached on specialized tissues called placenta inside the ovary.
Types of Placentation:
1. Marginal Placentation: Placenta forms a ridge along the ventral suture of ovary and ovules are borne on two rows (e.g., Pea).
2. Axile Placentation: Placenta is axial and ovules are attached to it in a multilocular ovary (e.g., Tomato, Lemon, China rose).
3. Parietal Placentation: Ovules develop on the inner wall of the ovary or peripheral part (e.g., Mustard, Argemone).
4. Free Central Placentation: Ovules are borne on central axis and septa are absent (e.g., Dianthus, Primrose).
5. Basal Placentation: Placenta develops at the base of ovary and a single ovule is attached (e.g., Sunflower, Marigold).
Textbook Chapter End Exercise Questions
| Feature | Racemose Inflorescence | Cymose Inflorescence |
|---|---|---|
| Main Axis Growth | Grows indefinitely and does not terminate in a flower. | Growth is limited; main axis terminates in a flower. |
| Arrangement of Flowers | Flowers are borne laterally in an acropetal succession (older flowers at base). | Flowers are borne in a basipetal order (older flower at apex). |
| Examples | Radish, Mustard, Lupin. | Jasmine, Bougainvillea, Solanum. |
Roots sometimes change their shape and structure and become modified to perform functions other than absorption and conduction of water and minerals (such as storage, mechanical support, and respiration).
• (a) Banyan tree: Prop roots—hanging structures that arise from heavy aerial stem branches and penetrate the soil to provide mechanical support.
• (b) Turnip: Fleshy tap root—modified for storage of reserve food material.
• (c) Mangrove trees (Rhizophora): Pneumatophores—respiratory roots growing vertically upward out of swampy soil to absorb oxygen for respiration.