Chapter Introduction
Morphology is the study of the external form and structure of organisms. In Chapter 5 of NCERT Class 11 Biology, you study the morphology of flowering plants (angiosperms) — their root, stem, leaf, inflorescence, flower, fruit, and seed. Understanding these structures is essential because plant identification, taxonomy, and economic uses all depend on morphological features. This chapter also covers three important families — Fabaceae, Solanaceae, and Liliaceae — whose floral diagrams and descriptions are frequent exam questions.
Angiosperms range from tiny Wolffia to tall Eucalyptus trees, yet they share a common body plan: root system (underground) and shoot system (aerial stem, leaves, flowers, fruits).
Key Definitions
| Term | Definition |
|---|
| Morphology | Study of external form and structure of organisms |
| Root cap | Thimble-like structure protecting the root tip |
| Region of meristematic activity | Zone of actively dividing cells at the root tip |
| Region of elongation | Zone above meristematic region where cells elongate |
| Region of maturation | Zone where cells differentiate; root hairs arise here |
| Inflorescence | Arrangement of flowers on the floral axis |
| Racemose | Indeterminate inflorescence — main axis grows indefinitely |
| Cymose | Determinate inflorescence — main axis terminates in a flower |
| Actinomorphic | Radially symmetric flower (can be divided into equal halves by any vertical plane) |
| Zygomorphic | Bilaterally symmetric flower (divided into equal halves by one plane only) |
| Aestivation | Arrangement of sepals or petals in a bud |
| Placentation | Arrangement of ovules inside the ovary |
| Pericarp | Wall of the fruit, developed from ovary wall |
| Epiphyllous | Stamens attached to the perianth (petal) |
| Epipetalous | Stamens attached to the petal |
The Root
Root Systems
| Feature | Taproot System | Fibrous Root System |
|---|
| Origin | Developed from radicle of embryo | Developed from base of stem (adventitious) |
| Found in | Dicotyledonous plants | Monocotyledonous plants |
| Primary root | Present, persists as dominant root | Short-lived, replaced by fibrous roots |
| Branching | Primary → secondary → tertiary roots | Fibrous roots of similar size |
| Example | Mustard, mango, banyan | Wheat, rice, onion |
Regions of the Root
1. Root cap — protects the tender apex; in some plants (pandanus) multiple root caps are present 2. Region of meristematic activity — cells are small, thin-walled, dense protoplasm, divide actively 3. Region of elongation — cells undergo rapid elongation and enlargement; responsible for root growth in length 4. Region of maturation — cells differentiate; root hairs develop here to absorb water and minerals
Modifications of Root
| Modification | Description | Function | Example |
|---|
| Prop roots | Roots hanging from branches, grow downward into soil | Mechanical support | Banyan (Ficus benghalensis) |
| Stilt roots | Roots arising from lower nodes of stem | Mechanical support | Sugarcane, maize |
| Tuberous roots | Swollen roots storing food | Storage of food | Carrot, radish, turnip, sweet potato |
| Pneumatophores | Vertically upward-growing roots with air pores | Respiration in swampy soil | Mangroves (Rhizophora) |
| Climbing roots | Roots arising from nodes for climbing | Climbing support | Betel (Piper betle), Pothos |
| Assimilatory roots | Green roots that perform photosynthesis | Photosynthesis | Tinospora, Trapa |
| Haustoria (parasitic roots) | Roots that penetrate host tissue to absorb nutrients | Parasitic nutrition | Cuscuta (dodder), Viscum |
The Stem
The stem is the ascending part of the axis bearing branches, leaves, flowers, and fruits. It has nodes (where leaves arise) and internodes (the portion between two nodes). A terminal bud at the apex allows growth in length.
Modifications of Stem
| Modification | Description | Function | Example |
|---|
| Tendril | Slender, spirally coiled structure | Climbing | Passiflora (passion flower), Vitis (grape) |
| Thorn | Hard, pointed, straight structure | Defence; reduces transpiration | Citrus, Bougainvillea |
| Phylloclade | Flattened green stem performing photosynthesis | Photosynthesis in arid conditions | Opuntia, Euphorbia |
| Rhizome | Underground stem growing horizontally | Storage, perennation | Ginger, turmeric, banana |
| Tuber | Swollen tip of underground stem branch | Storage of food | Potato (Solanum tuberosum) |
| Bulb | Disc-like stem with fleshy leaf bases | Storage | Onion, garlic, lily |
| Corm | Short, thick, vertical underground stem | Storage | Colocasia, Crocus |
| Stolon | Lateral branch from base creeping below ground | Vegetative propagation | Mint, jasmine |
| Offset | Short, thick, horizontal branch from leaf axil | Vegetative propagation | Pistia, Eichhornia (water hyacinth) |
| Runner | Slender lateral branch creeping on ground | Vegetative propagation | Oxalis, grasses |
| Sucker | Lateral branch from underground stem base | Vegetative propagation | Banana, Chrysanthemum |
The Leaf
A leaf consists of three main parts: leaf base (petiole base), petiole (stalk), and lamina (leaf blade).
- Stipules: Small lateral outgrowths at the leaf base; may be free, lateral, or inter-petiolar
- Petiole: Stalk that holds the lamina; in some plants it is flattened (Australian acacia) or swollen (pulpous petiole in Euphorbia)
- Lamina: Broad, green, flattened part; bears veins and veinlets
Venation
| Type | Description | Found in |
|---|
| Parallel venation | Veins run parallel to each other from base to apex | Monocots (grass, banana, bamboo) |
| Reticulate venation | Veins form a network or web | Dicots (peepal, hibiscus, rose) |
Phyllotaxy (Arrangement of Leaves)
| Type | Description | Example |
|---|
| Alternate | Single leaf at each node in a spiral | Sunflower, mustard |
| Opposite | Pair of leaves at each node, opposite each other | Calotropis, guava |
| Whorled | More than two leaves at a node in a whorl | Alstonia, Nerium |
Modifications of Leaf
| Modification | Description | Function | Example |
|---|
| Tendril | Leaf or leaflet modified into coiled thread | Climbing | Pea (Pisum), Lathyrus |
| Spine | Leaf modified into sharp pointed structure | Defence; reduces transpiration | Cactus, Opuntia |
| Pitcher | Lamina modified into pitcher with lid | Trapping insects (insectivorous) | Nepenthes |
| Succulent | Fleshy leaves storing water and mucilage | Storage in arid conditions | Aloe, Euphorbia |
| Phyllode | Petiole flattened and green, performing photosynthesis | Photosynthesis | Australian Acacia |
Inflorescence
The arrangement of flowers on the floral axis is called inflorescence. The floral axis is called peduncle.
| Feature | Racemose | Cymose |
|---|
| Main axis | Continues to grow (indeterminate) | Terminates in a flower (determinate) |
| Flower order | Acropetal (younger at tip, older at base) | Basipetal (older at tip, younger at base) |
| Flower number | Unlimited flowers | Limited flowers |
| Sub-types | Raceme, spike, corymb, umbel, capitulum | Solitary, cyme, biparous, multiparous |
| Example | Mustard (raceme), wheat (spike), sunflower (capitulum) | Calotropis (cyme), Hibiscus (solitary) |
Special types: verticillaster (Ocimum — whorled arrangement), hypanthodium (Ficus — cup-shaped receptacle with inner flowers), cyathium (Euphorbia — single female flower surrounded by many male flowers).
The Flower
The flower is the reproductive unit in angiosperms. It is a modified shoot where the apical meristem stops producing leaves and starts producing floral appendages. A typical flower has four whorls: calyx, corolla, androecium, gynoecium — arranged on the thalamus (receptacle).
Symmetry
- Actinomorphic (radially symmetric): Mustard, datura, chilli
- Zygomorphic (bilaterally symmetric): Pea, bean, Cassia
Sex of Flowers
| Type | Description | Example |
|---|
| Bisexual | Both androecium and gynoecium present | Hibiscus, mustard |
| Unisexual | Only androecium OR gynoecium present | Papaya, watermelon |
Position of Floral Parts on Thalamus
| Type | Description | Ovary position | Example |
|---|
| Hypogynous | Ovary is superior; other parts below ovary | Superior | Mustard, china rose |
| Perigynous | Ovary is half-inferior; cup-shaped thalamus | Half-inferior | Rose, peach |
| Epigynous | Ovary is inferior; other parts above ovary | Inferior | Guava, cucumber, ray floret of sunflower |
Aestivation (Arrangement of Petals/Sepals in Bud)
| Type | Description | Example |
|---|
| Valvate | Margins of adjacent petals touch but do not overlap | Calotropis |
| Twisted | One margin overlaps the next; direction is uniform | Cotton, china rose |
| Imbricate | Margins overlap irregularly; no fixed direction | Cassia, Bauhinia |
| Vexillary (papilionaceous) | Largest petal (standard) overlaps two wings, wings overlap keel | Pea, bean (Fabaceae) |
Placentation (Arrangement of Ovules in Ovary)
| Type | Description | Example |
|---|
| Marginal | Placenta forms a ridge along ventral suture; ovules in a row | Pea (Fabaceae) |
| Axile | Ovary partitioned; ovules attached to central axis | Tomato, lemon |
| Parietal | Ovules on inner wall of ovary; ovary unilocular | Mustard, Argemone |
| Free-central | Ovules on central column; no partitions | Dianthus, Primrose |
| Basal | Single ovule at the base of ovary | Sunflower, marigold |
The Fruit
A fruit is a mature or ripened ovary developed after fertilisation. The wall of the ovary becomes the pericarp (fruit wall), which may be dry or fleshy.
| Type | Description | Example |
|---|
| True fruit | Develops only from ovary | Mango, tomato |
| False fruit (pseudocarp) | Develops from ovary + other floral parts (thalamus) | Apple, strawberry, cashew |
Pericarp layers (in fleshy fruits): outer epicarp, middle mesocarp, inner endocarp. Example — mango: thin epicarp, fleshy mesocarp, stony endocarp (drupe).
The Seed
A seed is a fertilised ovule. It consists of a seed coat (testa + tegmen), an embryo, and stored food (endosperm or cotyledons).
| Feature | Dicot Seed | Monocot Seed |
|---|
| Cotyledons | Two | One (scutellum) |
| Endosperm | Usually absent (food in cotyledons) | Present (food in endosperm) |
| Seed coat | Testa + tegmen (separate) | Fused with pericarp (caryopsis) |
| Embryo | Embryonal axis + two cotyledons | Embryonal axis + scutellum + coleoptile + coleorhiza |
| Example | Pea, bean, gram | Maize, wheat, rice |
Embryo parts: radicle (future root), plumule (future shoot), hypocotyl (below cotyledonary node), epicotyl (above cotyledonary node). In monocots, coleoptile covers plumule and coleorhiza covers radicle.
Families of Flowering Plants
Fabaceae (Leguminosae — Pea Family)
| Feature | Description |
|---|
| Habit | Herbs, shrubs, trees; root with root nodules |
| Leaves | Alternate, pinnately compound; stipulate; leaf base pulvinus |
| Inflorescence | Racemose (raceme) |
| Calyx | 5 sepals, gamosepalous, valvate/imbricate |
| Corolla | 5 petals, polypetalous, papilionaceous (vexillary aestivation) — standard, wings, keel |
| Androecium | 10 stamens, diadelphous (9+1) |
| Gynoecium | Monocarpellary, unilocular, marginal placentation |
| Fruit | Legume (pod) |
| Examples | Pisum sativum (pea), Arachis hypogaea (groundnut), Cicer arietinum (gram) |
Solanaceae (Potato Family)
| Feature | Description |
|---|
| Habit | Herbs, shrubs, small trees |
| Leaves | Alternate, simple; exstipulate |
| Inflorescence | Solitary, cymose or axillary |
| Calyx | 5 sepals, gamosepalous, valvate |
| Corolla | 5 petals, gamopetalous, valvate |
| Androecium | 5 stamens, epipetalous, polyandrous |
| Gynoecium | Bicarpellary, syncarpous, ovary superior, bilocular, axile placentation |
| Fruit | Berry or capsule |
| Examples | Solanum tuberosum (potato), Lycopersicon (tomato), Capsicum (chilli), Datura, Petunia |
Liliaceae (Lily Family)
| Feature | Description |
|---|
| Habit | Perennial herbs with bulbs/rhizomes |
| Leaves | Alternate, simple, exstipulate; parallel venation |
| Inflorescence | Solitary or cymose (umbel) |
| Perianth | 6 tepals in two whorls, petaloid, gamophyllous or polyphyllous |
| Androecium | 6 stamens in two whorls, epiphyllous, polyandrous |
| Gynoecium | Tricarpellary, syncarpous, ovary superior, trilocular, axile placentation |
| Fruit | Capsule (rarely berry) |
| Examples | Lilium (lily), Allium cepa (onion), Aloe vera, Colchicum, Tulipa (tulip) |
Comparison: Fabaceae vs Solanaceae vs Liliaceae
| Feature | Fabaceae | Solanaceae | Liliaceae |
|---|
| Root | Nodules present | No nodules | Bulb/rhizome |
| Leaf venation | Reticulate | Reticulate | Parallel |
| Calyx/Corolla | Distinct (polypetalous) | Distinct (gamopetalous) | Tepals (undifferentiated) |
| Aestivation | Vexillary | Valvate | Valvate/imbricate |
| Stamen type | Diadelphous (9+1) | Epipetalous, polyandrous | Epiphyllous, polyandrous |
| Carpels | One (monocarpellary) | Two (bicarpellary) | Three (tricarpellary) |
| Placentation | Marginal | Axile | Axile |
| Fruit | Legume (pod) | Berry/capsule | Capsule |
Important Diagrams to Practise
1. T.S. of a dicot root — label: epidermis, cortex, endodermis, pericycle, vascular bundles (radial arrangement with exarch xylem) 2. L.S. of a flower — label: thalamus, calyx, corolla, androecium, gynoecium, ovary 3. V.S. of a typical angiospermic flower — label all four whorls and ovary position 4. Floral diagrams of Fabaceae, Solanaceae, Liliaceae — must practise from NCERT 5. L.S. of dicot seed (bean) — label: seed coat, micropyle, cotyledons, plumule, radicle, hypocotyl, epicotyl 6. L.S. of monocot seed (maize grain) — label: pericarp, endosperm, scutellum, coleoptile, plumule, coleorhiza, radicle
Common Mistakes to Avoid
1. Confusing root and stem modifications — rhizome, tuber, bulb, corm are stem modifications, not root. Carrot and radish are root modifications, not stem. 2. Mixing aestivation and placentation — aestivation is about petal arrangement in bud; placentation is about ovule arrangement in ovary. These are completely different concepts. 3. Calling false fruits true fruits — apple, strawberry, and cashew are false fruits because the edible part comes from the thalamus, not the ovary. 4. Confusing actinomorphic with zygomorphic — if the flower can be divided into equal halves by any vertical plane, it is actinomorphic. If only one plane gives equal halves, it is zygomorphic. 5. Wrong family identification — Fabaceae has diadelphous stamens and papilionaceous corolla; Solanaceae has epipetalous stamens and gamopetalous corolla; Liliaceae has epiphyllous stamens and tepals (no sepal-petal distinction). 6. Forgetting phyllotaxy vs venation — phyllotaxy is how leaves are arranged on the stem (alternate/opposite/whorled); venation is the pattern of veins on the lamina (parallel/reticulate).
Exam Tips
- 5-mark questions frequently ask for floral characteristics of a family (Fabaceae, Solanaceae, or Liliaceae). Write in the order: habit, leaves, inflorescence, calyx, corolla, androecium, gynoecium, fruit, examples. Draw the floral diagram.
- 3-mark questions often ask to differentiate racemose vs cymose, or taproot vs fibrous root. Use a table format.
- 1-mark questions target definitions: aestivation, placentation, phyllotaxy, actinomorphic, zygomorphic, epipetalous, epiphyllous.
- Diagram questions: practise the V.S. of a flower and the L.S. of dicot/monocot seeds — labels carry marks.
- Use NCERT terminology exactly. Do not substitute "petals and sepals" when the answer expects "tepals" (for Liliaceae).
Quick Revision Notes
- Root: taproot (dicot) vs fibrous (monocot); regions — cap, meristematic, elongation, maturation
- Root modifications: prop (banyan), stilt (sugarcane), tuberous (carrot), pneumatophores (mangroves)
- Stem modifications: tendril (Passiflora), thorn (Citrus), phylloclade (Opuntia), rhizome (ginger), tuber (potato), bulb (onion)
- Leaf: stipule, petiole, lamina; venation — parallel (monocot) vs reticulate (dicot)
- Phyllotaxy: alternate, opposite, whorled
- Leaf modifications: tendril (pea), spine (cactus), pitcher (Nepenthes), phyllode (Acacia)
- Inflorescence: racemose (indeterminate, acropetal) vs cymose (determinate, basipetal)
- Flower whorls: calyx, corolla, androecium, gynoecium
- Symmetry: actinomorphic vs zygomorphic; position: hypogynous vs perigynous vs epigynous
- Aestivation: valvate, twisted, imbricate, vexillary
- Placentation: marginal, axile, parietal, free-central, basal
- Fruit: true (mango) vs false (apple); pericarp: epicarp, mesocarp, endocarp
- Seed: dicot (two cotyledons, no endosperm) vs monocot (one cotyledon, endosperm present)
- Fabaceae: papilionaceous, diadelphous, marginal placentation, legume fruit
- Solanaceae: gamopetalous, epipetalous, bicarpellary, axile placentation, berry/capsule
- Liliaceae: tepals, epiphyllous, tricarpellary, axile placentation, capsule
