Morphology of Flowering Plants
'The study of form reveals function — morphology is the foundation of plant biology.' — Botany
1. Chapter Overview
MORPHOLOGY is the study of EXTERNAL form and structure. In flowering plants (Angiosperms), the body is DIVIDED into ROOT, STEM, LEAF, FLOWER, and FRUIT. This chapter examines EACH part in detail — its TYPICAL structure, VARIATIONS, and IMPORTANT modifications. Understanding morphology is ESSENTIAL for plant identification, classification, and understanding plant adaptations.
2. The Root System
Tap Root System
- PRIMARY root (radicle) grows downward → LATERAL roots (secondary, tertiary)
- Characteristics: Dicotyledons (Mustard, Mango, Banyan)
- Tap root: Thick, grows vertically; Branches arise from it
Fibrous Root System
- Primary root SHORT-LIVED; replaced by MANY roots from stem base
- Characteristics: Monocotyledons (Wheat, Rice, Maize, Onion)
Adventitious Root System
- Roots arise from PARTS OTHER than radicle (stem, leaves)
- Examples: Banyan (prop roots), Maize (stilt roots), Rhizophora (pneumatophores — breathing roots)
Regions of a Root
- Root cap: PROTECTS root tip
- Meristematic region: Cell division (growth)
- Elongation region: Cells LENGTHEN
- Maturation region: Root hairs, DIFFERENTIATION into tissues
Root Modifications
| Type | Modification | Function | Example |
|---|---|---|---|
| Storage | Swollen tap roots | Store FOOD | Carrot, Radish, Beetroot |
| Prop | Aerial roots from stem | SUPPORT | Banyan |
| Stilt | Roots from lower stem | ANCHORAGE | Maize, Sugarcane |
| Pneumatophore | Vertical roots (above water) | GAS EXCHANGE | Rhizophora (mangrove) |
3. The Stem
Characteristics
- AERIAL part, Bears LEAVES, BUDS, FLOWERS, and FRUITS
- Has NODES (leaf attachment) and INTERNODES
- POSITIVE phototropism; NEGATIVE geotropism
- Develops from PLUMULE
Stem Modifications
| Type | Example | Function |
|---|---|---|
| Underground | Potato (tuber), Ginger (rhizome), Onion (bulb), Colocasia (corm) | FOOD storage + Perennation |
| Aerial tendrils | Grapevine, Passionflower | CLIMBING |
| Thorns | Citrus, Bougainvillea | DEFENCE |
| Phylloclade | Opuntia (cactus), Asparagus | PHOTOSYNTHESIS (green, flattened stem) |
4. The Leaf
Structure
- Leaf base: Attaches to node; may have STIPULES
- Petiole: Stalk (present in petiolate; absent in sessile)
- Lamina (Blade): Expanded GREEN part. Midrib, veins (reticulate/parallel)
Venation
| Type | Pattern | Plant group |
|---|---|---|
| Reticulate | Net-like | Dicotyledons |
| Parallel | Parallel veins | Monocotyledons |
Leaf Types
- Simple: Lamina UNDIVIDED (mango, banyan)
- Compound: Lamina DIVIDED into leaflets
- Pinnately compound: Leaflets on RACHIS (neem, rose)
- Palmately compound: Leaflets radiate from TIP (cotton, silk cotton)
Phyllotaxy (Leaf Arrangement on Stem)
| Type | Pattern | Example |
|---|---|---|
| Alternate | ONE leaf per node | Sunflower, Mustard |
| Opposite | TWO leaves per node | Calotropis, Guava |
| Whorled | THREE+ leaves per node | Alstonia |
Leaf Modifications
| Modification | Function | Example |
|---|---|---|
| Tendrils | Climbing | Pea |
| Spines | Defence | Cactus |
| Scales | Protection | Onion bulb |
| Leaf pitcher | Insect trapping | Nepenthes (pitcher plant) |
5. The Inflorescence
Types
| Type | Pattern | Examples |
|---|---|---|
| Racemose | Main axis CONTINUES to grow; flowers in ACROPETAL succession | Mustard, Radish, Sunflower (head) |
| Cymose | Main axis STOPS at a flower; flowers in BASIPETAL succession | Cotton, Jasmine, Carnation |
Special Types
- Spike: Sessile flowers (wheat, barley)
- Head (Capitulum): Sunflower family
- Catkin: Pendulous spike (willow)
- Umbel: Flowers on equal stalks from one point (coriander)
6. The Flower (Essential for Reproduction)
Floral Parts (Four Whorls)
- Calyx (Sepals): Outermost, PROTECTIVE (green or coloured)
- Corolla (Petals): ATTRACTIVE, helps pollination
- Androecium (Stamens): MALE reproductive part (filament + anther)
- Gynoecium (Carpels/Pistils): FEMALE reproductive part (stigma + style + ovary)
Flower Symmetry
- Actinomorphic: Radial symmetry (mustard, tulip)
- Zygomorphic: Bilateral symmetry (pea, ocimum)
Position of Ovary (Floral Parts)
| Type | Ovary Position | Example |
|---|---|---|
| Hypogynous | Superior ovary; above other whorls | Mustard, China rose |
| Perigynous | Half-inferior; ovary surrounded by hypanthium | Plum, Rose |
| Epigynous | Inferior ovary; below other whorls | Sunflower, Apple |
7. The Fruit
- Definition: Matured OVARY developed after FERTILISATION
- Pericarp: Wall of fruit (epicarp, mesocarp, endocarp)
- Types:
- True fruit: From ovary only (mango, tomato)
- False fruit (Pseudocarp): Other parts also contribute (apple, strawberry)
- Parthenocarpic fruit: Without FERTILISATION (banana, grapes)
8. The Seed
Structure
- Seed coat (Testa + Tegmen): Protective covering
- Embryo: Radicle (future root) + Plumule (future shoot) + Cotyledons
- Endosperm: Nutritive tissue
| Type | Examples |
|---|---|
| Albuminous (with endosperm) | Castor, Maize, Wheat |
| Exalbuminous (without endosperm) | Pea, Bean, Groundnut |
9. Common Mistakes
- Carrot and radish are NOT roots? They ARE tap roots modified for storage — you eat the ROOT, not stem
- Potato tuber is a STEM, not a root: It has NODES (eyes) — roots do not have nodes
- Flower parts are MODIFIED leaves: Sepals, petals, stamens, carpels are all derived from leaf primordia
- Apple is a FALSE fruit: The fleshy part is the THALAMUS, not the ovary wall
- Hypogynous ≠ epigynous: In hypogynous, ovary is ABOVE (superior); in epigynous, ovary is BELOW (inferior)
10. CBSE Exam Focus
- Root and stem modifications with examples (3/5-mark)
- Leaf — venation, phyllotaxy, modifications (3-mark)
- Inflorescence types — racemose vs cymose (3-mark)
- Flower structure — whorls, symmetry, ovary position (5-mark)
- Fruit types — true, false, parthenocarpic (1/3-mark)
11. Self-Test (5+ Q&A)
Q1: How would you distinguish a tuber (potato) from a root? A: Potato tuber has NODES (eyes) with buds — a characteristic of STEM. Roots do NOT have nodes or buds.
Q2: Differentiate between racemose and cymose inflorescence. A: Racemose: Main axis GROWS CONTINUOUSLY; flowers acropetal (oldest at bottom). Cymose: Axis STOPS at a flower; flowers basipetal (oldest at top).
Q3: What is a false fruit? Give one example. A: A fruit formed NOT only from the ovary but also from other floral parts (receptacle). Example: APPLE (fleshy part = thalamus; core = ovary).
Q4: What is phyllotaxy? Describe its types. A: Arrangement of leaves on stem. Types: alternate (one/node), opposite (two/node), whorled (three+/node).
Q5: Write the floral formula of a typical dicot flower with all whorls present and ovary superior. A: Br ⚥ % ⚥ K(5) C5 A5 G(2) (example of a generalised dicot — numbers may vary).
12. Conclusion
Plant morphology PROGRESSES from underground (root) → aerial (stem) → photosynthetic (leaf) → reproductive (flower → fruit → seed). Each structure is ADAPTED for specific functions — roots anchor and absorb, stems support and transport, leaves photosynthesise, flowers reproduce. MODIFICATIONS reveal how plants ADAPT to diverse environments. This morphological knowledge is the FOUNDATION for plant identification, taxonomy, and understanding the ECOLOGICAL roles of different plant species.
