Chapter 6 — Morphology of Flowering Plants
Key Concepts Quick Recap
| Term | Definition |
|---|
| Morphology | Study of external form and structure of plants |
| Root | Underground organ; absorbs water and minerals; no nodes/buds/leaves |
| Stem | Aerial axis; bears nodes and internodes; has buds and leaves |
| Leaf | Lateral appendage of stem; primary photosynthetic organ |
| Phyllotaxy | Arrangement of leaves on a stem |
| Stipule | Small leaf-like appendages at leaf base |
| Inflorescence | Arrangement of flowers on a floral axis |
| Flower | Modified shoot for sexual reproduction |
| Fruit | Ripened ovary after fertilisation |
| Seed | Ripened ovule containing embryo |
I. Choose the Best Answer (MCQs)
1. The root system in which the primary root is replaced by adventitious roots is called: (a) Tap root system (b) Fibrous root system (c) Adventitious root system (d) Prop root system
Answer(b) Fibrous root system In monocots (grass, rice, wheat), the primary root (from radicle) is short-lived and replaced by a mass of fibrous adventitious roots arising from the stem base — fibrous root system.
2. Prop roots in Banyan tree are a modification of: (a) Underground stem (b) Aerial roots (c) Tap root (d) Fibrous root
Answer(b) Aerial roots Prop roots (pillar roots) in Banyan (Ficus benghalensis) develop from aerial branches and grow downward into soil — they provide mechanical support to the spreading canopy. The Banyan forms a natural pillar structure.
3. A leaf with a single lamina is called: (a) Compound leaf (b) Simple leaf (c) Pinnate leaf (d) Palmate leaf
Answer(b) Simple leaf Simple leaf: single lamina, which may be incised but not completely divided to the midrib. Compound leaf: lamina completely divided into distinct leaflets (pinnate or palmate compound).
4. The floral formula of a bisexual, actinomorphic flower with 5 sepals, 5 petals, many stamens, and a superior ovary is: (a) ⊕ K5 C5 A∞ G̲ (b) ⊕ K5 C5 A∞ G̅ (c) % K5 C5 A∞ G̅ (d) ⊕ K(5) C(5) A5+5 G̅
Answer(b) ⊕ K5 C5 A∞ G̅ ⊕ = actinomorphic (regular); K5 = 5 free sepals; C5 = 5 free petals; A∞ = many stamens; G̅ = superior ovary (line above G = superior/hypogynous).
5. A cymose inflorescence is one in which: (a) The main axis grows indefinitely (b) The main axis ends in a flower; growth continues from lateral buds (c) Flowers are in a spike (d) The axis is flattened
Answer(b) Main axis ends in a flower; growth continues from lateral buds Cymose (definite) inflorescence: main axis terminates in a flower; growth continues from axillary buds → determinate growth. Racemose (indefinite) inflorescence: main axis grows continuously; flowers open from base upward → indeterminate growth.
6. Parthenocarpy refers to: (a) Development of fruit with seeds (b) Development of fruit without fertilisation (c) Fruit ripening (d) Dispersal of fruits
Answer(b) Development of fruit without fertilisation Parthenocarpic fruits develop from the ovary without fertilisation → seedless fruits. Examples: Banana, seedless grapes, some varieties of citrus. Induced artificially by auxins (IAA, gibberellins).
7. Which of the following is a false fruit (pseudocarp)? (a) Mango (b) Guava (c) Apple (d) Orange
Answer(c) Apple In apple, the fleshy edible part develops from the thalamus (receptacle), not the ovary — hence a false fruit (pseudocarp). True fruit develops only from the ovary. Other false fruits: strawberry (thalamus), cashew (peduncle). Mango and guava are true fruits.
II. Short Answer Questions
Q1. What are the modifications of tap roots? Give two examples each.
Answer
| Modification | Function | Example |
|---|
| Fusiform (spindle-shaped) | Food storage | Radish (Raphanus sativus) |
| Napiform (turnip-shaped) | Food storage | Turnip (Brassica rapa) |
| Conical | Food storage | Carrot (Daucus carota) |
| Nodulated | Nitrogen fixation (houses Rhizobium) | Groundnut, Pea |
| Pneumatophores | Breathing roots (gas exchange) in waterlogged soil | Rhizophora (mangrove) |
| Prop/stilt roots | Mechanical support | Pandanus |
| Aerial/epiphytic | Absorb moisture from air (chlorophyll present) | Orchids (Vanda) |
Q2. Distinguish between simple and compound leaves.
Answer
| Feature | Simple Leaf | Compound Leaf |
|---|
| Lamina | Single, may be lobed/incised | Divided completely into leaflets |
| Leaflets | Absent | Present; each leaflet has its own petiolule |
| Bud | Axillary bud in leaf axil | Axillary bud only in axil of whole leaf, not leaflets |
| Examples | Mango, Banyan, Peepal | Neem (pinnate), Silk Cotton (palmate) |
Types of compound leaves:
- Pinnate compound: leaflets on both sides of rachis (Neem, Rose).
- Palmate compound: leaflets arise from tip of petiole (Silk Cotton, Cannabis).
Q3. What is inflorescence? Describe the types with examples.
Answer
Inflorescence is the arrangement of flowers on a floral axis (peduncle).
1. Racemose (indefinite): Main axis grows indefinitely; younger flowers at apex, older at base.
| Type | Features | Example |
|---|
| Raceme | Stalked flowers on elongated axis | Radish |
| Spike | Sessile flowers on elongated axis | Wheat |
| Catkin | Spike of unisexual flowers | Mulberry |
| Spadix | Spike with fleshy axis and leafy spathe | Banana, Colocasia |
| Corymb | Lower flowers long-stalked, all flowers at same level | Cauliflower |
| Umbel | All flower stalks arise from one point | Coriander |
| Capitulum/Head | Sessile flowers on flat/convex receptacle | Sunflower |
2. Cymose (definite): Main axis ends in a flower; growth from lateral buds.
| Type | Features | Example |
|---|
| Monochasial | One branch at each node | Datura |
| Dichasial | Two branches at each node | Teak, Calotropis |
| Polychasial | Many branches at each node | Croton |
III. Long Answer
Q1. Describe the parts of a typical flower and their functions.
Answer
A typical flower has four whorls attached to the thalamus (receptacle):
1. Calyx (outermost whorl):
Answer
- Consists of sepals (collectively = calyx).
- Usually green and leaf-like.
- Function: protection of flower bud.
- Free sepals (polysepalous): Mustard; fused (gamosepalous): Datura.
2. Corolla (second whorl):
Answer
- Consists of petals.
- Often brightly coloured for pollinator attraction.
- Free (polypetalous): Rose, Cassia; fused (gamopetalous): Datura, Brinjal.
3. Androecium (third whorl — male):
Answer
- Consists of stamens (anther + filament + connective).
- Anther produces pollen grains.
- Number and arrangement vary widely.
4. Gynoecium (innermost whorl — female):
Answer
- Consists of carpels (pistil = stigma + style + ovary).
- Ovary contains ovules → seeds after fertilisation.
- Superior ovary (hypogynous): Mustard; inferior (epigynous): Guava.
Accessory whorls: Calyx and Corolla. Essential whorls: Androecium and Gynoecium.
Common Mistakes
- Saying Banyan has tap roots — Banyan's prop roots are aerial adventitious roots.
- Confusing leaflets (compound leaf) with leaves — axillary bud is in the leaf axil, not leaflet axil.
- Calling apple a true fruit — it is a pseudocarp/false fruit (fleshy part from thalamus).
- Confusing racemose (indefinite) and cymose (definite): remember cymose = main axis ENDS in a flower.
Exam Checklist
- Root modifications table: fusiform (radish), napiform (turnip), nodulated (legumes), pneumatophores (mangrove).
- Simple vs compound leaf: bud position is the key diagnostic.
- Inflorescence types: racemose vs cymose; 4 examples each.
- Floral formula symbols: ⊕ (actinomorphic), % (zygomorphic), G̅ (superior), G̲ (inferior).
- False fruits: Apple, Strawberry, Cashew.
