Morphology of Flowering Plants — Biology Class 11 Notes (CBSE & HBSE)
Free NCERT Biology notes for Morphology of Flowering Plants (Class 11) on Siksha Sarovar, aligned to CBSE and Haryana Board (HBSE). This chapter is broken into 3 topics with clear explanations, formulas, solved examples and board-pattern practice — free to read, no sign-up required.
Board exam focus — Morphology of Flowering Plants (CBSE & HBSE)
This chapter describes the external form (morphology) of angiosperms — the root, stem and leaf and their modifications, the inflorescence and the flower with its parts, aestivation and placentation, followed by the fruit and seed. It introduces the semi-technical description of a typical flowering plant, the floral diagram and floral formula, and the salient features of three economically important families — Fabaceae, Solanaceae and Liliaceae.
The Root, Stem, Leaf and Their Modifications
The Root
The root is the non-green, descending, underground part of a plant.
| Root system | Origin | Found in |
|---|---|---|
| Tap root | Develops from the radicle; one main root with branches | Dicots (e.g., mustard) |
| Fibrous root | Develops from the base of the stem; many fine roots | Monocots (e.g., wheat) |
| Adventitious root | Arises from parts other than the radicle | Monstera, grass, banyan |
Regions of the root (root tip to base): root cap → region of meristematic activity → region of elongation → region of maturation (bears root hairs).
Modifications of Roots
- Storage: tap roots store food — fusiform (radish), conical (carrot), napiform (turnip).
- Support: prop roots (banyan), stilt roots (maize, sugarcane).
- Respiration: pneumatophores in Rhizophora (mangroves) grow up for gaseous exchange.
The Stem
The stem is the ascending axis bearing nodes, internodes, buds, leaves, flowers and fruits.
Modifications of Stems
| Function | Modification | Example |
|---|---|---|
| Storage | Underground stems — rhizome, corm, tuber, bulb | Ginger, Colocasia, potato, onion |
| Support | Stem tendrils | Gourd, grapevine |
| Protection | Stem thorns | Citrus, Bougainvillea |
| Vegetative propagation | Runner, offset, sucker, stolon | Grass, Pistia, mint |
| Photosynthesis | Flattened/cylindrical green stems (phylloclade) | Opuntia, Euphorbia |
NEET trap: The 'eyes' of a potato are nodes bearing axillary buds — proof that the potato is an underground stem, not a root.
The Leaf
The leaf is a lateral, flattened structure borne on the node, mainly for photosynthesis. Parts: leaf base, petiole and lamina.
Venation
- Reticulate venation — network of veins (dicots).
- Parallel venation — veins run parallel (monocots).
Types of Leaves
- Simple leaf — lamina undivided or, if incised, incisions do not reach the midrib.
- Compound leaf — lamina divided into leaflets; pinnately compound (neem) or palmately compound (silk cotton).
Phyllotaxy (arrangement of leaves)
- Alternate (China rose), opposite (Calotropis), whorled (Alstonia).
Modifications of Leaves
- Tendrils (pea), spines (Opuntia), storage (onion fleshy leaves), pitcher (Nepenthes) for insect capture.
Inflorescence, the Flower, Aestivation and Placentation
Inflorescence
The arrangement of flowers on the floral axis is called inflorescence. Two main types:
| Type | Growth of main axis | Flower opening sequence | Example |
|---|---|---|---|
| Racemose | Main axis continues to grow; flowers borne laterally | Acropetal (older below, younger above) | Radish, mustard |
| Cymose | Main axis ends in a flower; growth limited | Basipetal (older in centre/top) | Jasmine, Solanum |
The Flower
A flower is a modified shoot meant for sexual reproduction. A typical flower has four whorls borne on the thalamus:
- Calyx — sepals (green, protective).
- Corolla — petals (often coloured, attract pollinators).
- Androecium — stamens (male; anther + filament).
- Gynoecium — carpels/pistil (female; stigma, style, ovary).
Symmetry of the Flower
- Actinomorphic (radial symmetry) — mustard, Datura.
- Zygomorphic (bilateral symmetry) — pea, Cassia.
Position of Floral Parts on Thalamus
- Hypogynous — ovary superior (mustard, China rose).
- Perigynous — ovary half-inferior (rose, plum).
- Epigynous — ovary inferior (guava, cucumber, sunflower).
Aestivation
The mode of arrangement of sepals or petals in the floral bud is aestivation.
| Aestivation | Description | Example |
|---|---|---|
| Valvate | Margins just touch, no overlap | Calotropis |
| Twisted | One margin overlaps the next, contorted | China rose, Cotton |
| Imbricate | Overlapping but not in a definite direction | Cassia, Gulmohur |
| Vexillary (papilionaceous) | Large posterior (standard) covers two laterals, which cover two anterior (keel) petals | Pea, bean |
Placentation
The arrangement of ovules within the ovary is placentation.
| Type | Feature | Example |
|---|---|---|
| Marginal | Placenta forms a ridge along the ventral suture, one chamber | Pea |
| Axile | Placenta is axial, ovary multilocular | China rose, tomato, lemon |
| Parietal | Ovules on the inner wall, one chamber (becomes two by false septum) | Mustard, Argemone |
| Free central | Ovules on the central axis, no septa | Dianthus, Primrose |
| Basal | Single ovule at the base | Sunflower, marigold |
NEET trap: Tomato shows axile placentation, whereas mustard shows parietal placentation — a frequently asked distinction.
Fruit, Seed, Floral Formula and Major Families
The Fruit
A fruit is the mature/ripened ovary developed after fertilisation. A fruit consists of a pericarp (fruit wall) and seeds.
- True fruit — develops only from the ovary (mango).
- False fruit — other floral parts (e.g., thalamus) also form part of the fruit (apple).
- Parthenocarpic fruit — fruit formed without fertilisation, hence seedless (banana).
In a drupe (mango, coconut) the pericarp is differentiated into outer epicarp, middle fleshy mesocarp and stony inner endocarp.
The Seed
The seed is the fertilised, mature ovule.
| Seed type | Cotyledons | Example |
|---|---|---|
| Dicotyledonous | Two cotyledons | Gram, pea, bean |
| Monocotyledonous | One cotyledon | Maize, wheat, rice |
A dicot seed has a seed coat (testa + tegmen), hilum, micropyle, two cotyledons and an embryo axis (radicle + plumule). A monocot seed (maize) has a single cotyledon (scutellum) and endosperm separated by an aleurone layer.
Semi-technical Description and Floral Formula
A typical flowering plant is described semi-technically covering its habit, root, stem, leaf, inflorescence and floral features. The flower is summarised in a floral formula using symbols:
| Symbol | Meaning |
|---|---|
| Br | Bracteate |
| ⊕ | Actinomorphic (radial) |
| % | Zygomorphic (bilateral) |
| K | Calyx |
| C | Corolla |
| P | Perianth (calyx + corolla not differentiated) |
| A | Androecium |
| G / Ḡ | Gynoecium (superior / inferior ovary) |
| ( ) | Fusion |
Major Families
Family Fabaceae (Papilionoideae of Leguminosae)
- Vegetative: tap root with root nodules; stem erect or climber; leaves pinnately compound with pulvinus; stipulate.
- Floral: zygomorphic, bisexual; calyx 5 (gamosepalous); corolla papilionaceous (1 standard + 2 wings + 2 keel); stamens 10, diadelphous; gynoecium monocarpellary, ovary superior, marginal placentation.
- Floral formula: % K(5) C1+2+(2) A(9)+1 G1.
- Examples / uses: gram, pea, Sesbania, Indigofera (dye); pulses, oil, fodder.
Family Solanaceae
- Vegetative: tap root; herbs/shrubs; leaves alternate, exstipulate.
- Floral: actinomorphic, bisexual; calyx 5 (gamosepalous, persistent); corolla 5 (gamopetalous); stamens 5, epipetalous; gynoecium bicarpellary, syncarpous, ovary superior, axile placentation, placenta swollen with many ovules.
- Floral formula: ⊕ K(5) C(5) A5 G(2).
- Examples / uses: potato, tomato, brinjal, Datura, tobacco.
Family Liliaceae
- Vegetative: perennial herbs with bulbs/corms/rhizomes; leaves mostly basal, parallel venation.
- Floral: actinomorphic, bisexual; perianth of 6 tepals (3+3); stamens 6; gynoecium tricarpellary, syncarpous, ovary superior, axile placentation, trilocular.
- Floral formula: ⊕ P(3+3) A(3+3) G(3).
- Examples / uses: Allium (onion, garlic), Aloe, tulip, Gloriosa.
NEET trap: Fabaceae has diadelphous stamens (9 fused + 1 free) and a papilionaceous corolla — both are favourite identification cues.
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Concept explanations, key formulas and definitions, fully solved examples and board-pattern practice questions for Morphology of Flowering Plants.