Chapter 3: Morphology of Flowering Plants

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The Root

Types and Functions

• Dicots: Primary root from radicle elongates into a primary root with lateral secondary and tertiary roots forming the taproot system.

• Monocots: Primary root is short-lived; replaced by many roots from stem base forming fibrous root system.

• Adventitious roots arise from parts other than radicle (e.g., stems, leaves).

• Functions:

  • Absorb water and minerals

  • Anchor plant to soil

  • Store reserve food

  • Synthesize some growth regulators

Memory Aids

• Taproot = main root + branches (dicots)

• Fibrous = many thin roots from stem base (monocots)

• Adventitious = roots from non-root parts

Quick Checkpoints

• What forms the taproot system?

• Which root system replaces the primary root in monocots?

• Define adventitious roots.

• List main functions of roots.

Regions of Root

Structure and Functions

• Root cap (calyptra): Protects root tip during soil penetration; absent in epiphytes, parasites, hydrophytes, mycorrhizal roots.

• Region of meristematic activity: Small, thin-walled cells dividing rapidly for root growth.

• Region of elongation: Cells elongate, pushing root tip forward.

• Region of differentiation (maturation): Cells mature; root hairs develop here to absorb water and minerals; root hairs absent in mycorrhizal roots.

• Region of mature cells: Cells no longer change; impermeable to water; anchors plant firmly.

Memory Aids

• Root cap = soil shield

• Meristematic region = cell division zone

• Elongation region = length growth

• Differentiation region = root hairs form

• Mature region = anchorage

Quick Checkpoints

• What is the function of the root cap?

• Where does cell division occur in the root?

• Which region forms root hairs?

• What is the role of mature cells in roots?

Modifications of Root

Types and Examples

• Storage roots: Swollen roots store food.

  • Tap roots: carrot, turnip

  • Adventitious roots: sweet potato

• Support roots:

  • Prop roots: banyan tree (support hanging branches)

  • Stilt roots: maize, sugarcane (support stem)

• Respiratory roots (pneumatophores): Grow upwards in swampy plants (e.g., Rhizophora, Sonneratia) to absorb oxygen.

Memory Aids

• Storage roots: swollen for food (carrot, sweet potato)

• Support roots: prop and stilt roots stabilize plant

• Respiratory roots: pneumatophores for oxygen in waterlogged soil

Quick Checkpoints

• Name roots modified for food storage.

• What are prop roots and their function?

• Which roots help in respiration in swampy plants?

• Give examples of stilt roots.

Stem Structure

Key Features

• Stem is the ascending axis bearing branches, leaves, flowers, and fruits.

• Develops from the plumule of the embryo in a germinating seed.

• Has nodes (points where leaves attach) and internodes (segments between nodes).

• Young stems are green; mature stems often become woody and brown.

• Bears buds: terminal (at tip) or axillary (in leaf axils).

• Bud is a compact, undeveloped shoot with a growing point and young leaves.

Memory Aids

• Plumule → Stem origin in seed.

• Nodes = leaf attachment points; Internodes = spaces between nodes.

• Buds = undeveloped shoots for growth.

Quick Checkpoints

• What is the origin of the stem in a seed?

• Define nodes and internodes.

• What are terminal and axillary buds?

Stem Functions

Main Roles

• Supports and spreads branches bearing leaves, flowers, and fruits.

• Conducts water, minerals, and photosynthates between roots and leaves.

• Some stems store food and aid in vegetative propagation.

• Provides mechanical support and protection.

Memory Aids

• Stem = Support + Transport + Storage + Propagation.

Quick Checkpoints

• List the main functions of the stem.

• How does the stem aid in vegetative propagation?

Modifications of Stem

Types and Examples

• Tuber: Underground swollen stem storing food; e.g., Potato. Also aids vegetative propagation.

• Rhizome: Horizontal underground stem with nodes, internodes, scaly leaves, and buds; e.g., Zingiber officinale (Ginger), Curcuma longa (Turmeric).

• Corm: Vertical, unbranched, underground stem storing food and aiding reproduction; e.g., Colocasia, Amorphophallus.

• Tendrils: Slender, spirally coiled stems from axillary buds for climbing; e.g., Cucumber, Grapevine.

• Thorns: Modified axillary buds for protection; e.g., Citrus, Bougainvillea.

• Phylloclades: Flattened or fleshy stems with chlorophyll for photosynthesis; e.g., Opuntia, Euphorbia.

• Cladodes: One internode long, leaf-like phylloclades capable of photosynthesis; e.g., Ruscus, Asparagus.

• Runner: Horizontal underground stems spreading to new areas; e.g., Grass, Strawberry.

• Stolon: Slender lateral branch growing aerially then touching ground for propagation; e.g., Mint, Jasmine.

• Offset: Lateral branch with short internodes, rosette leaves, and roots; e.g., Pistia, Eichhornia.

• Sucker: Lateral branches from basal underground stem growing horizontally then upward; e.g., Banana, Pineapple, Chrysanthemum.

Memory Aids

• Tuber = Potato; Rhizome = Ginger; Corm = Colocasia.

• Tendrils climb; Thorns protect; Phylloclades photosynthesize.

• Runner and Stolon spread plants vegetatively.

Quick Checkpoints

• Differentiate tuber, rhizome, and corm.

• What is the function of tendrils?

• Define phylloclade and cladode.

• How do runners and stolons aid propagation?

Thorns, Spines, Prickles, and Bristles

Characteristics and Differences

• Thorns: Modified stems with vascular tissue and thick-walled cells; protect plants from animals.

• Spines: Modified leaves or leaf parts with vascular strands but less developed bark.

• Prickles: Superficial outgrowths of stem or leaves without vascular tissue; easily detached.

• Bristles: Stiff hairs thickened by silica or calcium carbonate deposits.

Memory Aids

• Thorns = stem origin; Spines = leaf origin; Prickles = surface outgrowths; Bristles = stiff hairs.

Quick Checkpoints

• Identify the origin of thorns and spines.

• How do prickles differ from thorns?

• What are bristles composed of?

The Leaf

Structure and Function

• Leaf is a lateral, flattened structure on stem nodes, bearing an axillary bud that can grow into a branch.

• Leaves develop from shoot apical meristem in acropetal order and are key for photosynthesis.

• Main parts: leaf base (attaches leaf to stem), petiole (stalk holding lamina), and lamina (green blade with veins).

• Leaf base may have stipules (small leaf-like structures).

• In monocots (e.g., maize), leaf base forms a sheath around stem; in some legumes, it swells into a pulvinus.

• Petiole allows leaf blade to flutter, aiding cooling and gas exchange.

• Lamina has a midrib (central vein) and veins that provide support and transport water, minerals, and food.

Memory Aids

• Leaf parts: Base, Petiole, Lamina (BPL).

• Axillary bud at leaf base can grow into branch.

• Monocot leaf base = sheath; legume leaf base = pulvinus.

Quick Checkpoints

• What are the three main parts of a leaf?

• Where is the axillary bud located?

• How does petiole aid leaf function?

Venation

Types and Characteristics

• Venation: arrangement of veins and veinlets in leaf lamina.

• Reticulate venation: veins form a network; typical of dicots.

• Parallel venation: veins run side by side; typical of monocots.

Memory Aids

• Dicots = Reticulate (network).

• Monocots = Parallel veins.

Quick Checkpoints

• Define venation.

• Which venation type is found in dicots?

• Which venation type is found in monocots?

Types of Leaves

Simple and Compound Leaves

• Simple leaf: lamina entire or incisions not reaching midrib; axillary bud present at petiole axil.

• Compound leaf: lamina incisions reach midrib, dividing into leaflets; no axillary bud at leaflet axil.

• Compound leaves are pinnately or palmately compound.

• Pinnately compound: leaflets on a common axis (rachis), e.g., Azadirachta indica (neem).

• Palmately compound: leaflets attached at a single point at petiole tip, e.g., Bombax ceiba (silk cotton).

Memory Aids

• Simple = one lamina; Compound = multiple leaflets.

• Pinnate = feather-like; Palmate = hand-like.

Quick Checkpoints

• Difference between simple and compound leaves.

• Characteristics of pinnately compound leaves.

• Characteristics of palmately compound leaves.

Phyllotaxy

Leaf Arrangement on Stem

• Phyllotaxy: arrangement of leaves on stem or branch.

• Alternate: one leaf per node, alternating sides (e.g., Hibiscus rosa-sinensis).

• Opposite: two leaves per node, opposite each other (e.g., Psidium guajava).

• Whorled: more than two leaves per node forming a circle (e.g., Alstonia).

Memory Aids

• Alternate = one leaf/node.

• Opposite = two leaves/node.

• Whorled = multiple leaves/node.

Quick Checkpoints

• Define phyllotaxy.

• Identify types of phyllotaxy with examples.

• How does phyllotaxy affect sunlight capture?

Modifications of Leaves

Adaptations Beyond Photosynthesis

• Leaves modified for functions other than photosynthesis.

• Tendrils for climbing: e.g., Pisum sativum (garden pea).

• Spines for defense: e.g., cactus, Opuntia.

• Fleshy leaves for food storage: e.g., onion, garlic.

• In some plants (e.g., Australian acacia), small leaves replaced by green, food-synthesizing petioles.

• Insectivorous plants (e.g., Nepenthes, Dionaea) have leaves modified to trap and digest insects.

Memory Aids

• Tendrils = climbing; Spines = defense.

• Fleshy leaves = storage.

• Petiole photosynthesis in some plants.

• Insectivorous leaves = insect traps.

Quick Checkpoints

• List leaf modifications and their functions.

• Examples of plants with tendrils and spines.

• How do insectivorous plants modify leaves?

Inflorescence

Types and Characteristics

• A flower is a modified shoot where the shoot apical meristem becomes a floral meristem.

• Inflorescence is the arrangement of flowers on the floral axis.

• Two main types: Racemose and Cymose.

• Racemose: Main axis grows continuously; flowers develop laterally in acropetal succession (younger at top).

• Cymose: Main axis ends in a flower; growth is limited; flowers develop in basipetal order (older at top/center).

Memory Aids

• Racemose = \"Race\" continues growing; flowers from bottom to top.

• Cymose = \"Cycle\" ends; main flower stops growth.

Quick Checkpoints

• What defines racemose inflorescence growth?

• How does flower succession differ in cymose type?

• Which type has the main axis terminating in a flower?

Special Types of Inflorescence

Descriptions

• Hypanthodium: Fleshy receptacle forming a hollow structure with an apical opening guarded by scales; e.g., Ficus religiosa, Ficus benghalensis.

• Verticillaster: Modified condensed dichasial cyme with two whorls of 3–9 flowers on either side of a node; e.g., Ocimum sanctum.

• Cyathium: Inflorescence resembling a single flower; bracts fuse into a cup enclosing one female flower surrounded by many male flowers; e.g., Euphorbia pulcherrima.

Memory Aids

• Hypanthodium = Hollow fig structure with guarded opening.

• Verticillaster = Whorled pairs of flowers at nodes.

• Cyathium = Cup-shaped flower-like inflorescence.

Quick Checkpoints

• What is the structure of hypanthodium?

• How are flowers arranged in verticillaster?

• What makes cyathium appear like a single flower?

The Flower

Structure and Types

• Flower is the sexual reproductive unit in angiosperms.

• Four whorls on thalamus: calyx, corolla (accessory), androecium, gynoecium (reproductive).

• Perianth: when calyx and corolla are indistinct (e.g., lily).

• Bisexual flower: has both androecium and gynoecium.

• Unisexual flower: has either stamens or carpels only.

• Complete flower: all four whorls present; incomplete: any whorl missing.

• Symmetry types:

  • Actinomorphic: radial symmetry (e.g., mustard).

  • Zygomorphic: bilateral symmetry (e.g., pea).

  • Asymmetric: no symmetry (e.g., Canna).

• Floral appendages in multiples: trimerous (3), tetramerous (4), pentamerous (5).

• Bracteate flowers have bracts at pedicel base; ebracteate lack bracts.

Memory Aids

• Bisexual = both sexes; Unisexual = one sex.

• Actinomorphic = Any plane symmetry; Zygomorphic = One plane symmetry.

• Complete = 4 whorls; Incomplete = missing whorls.

Quick Checkpoints

• Identify flower whorls and their functions.

• Distinguish bisexual and unisexual flowers.

• Classify flower symmetry types.

• Recognize complete vs incomplete flowers.

Flower Classification Based on Ovary Position

Types and Examples

• Hypogynous: ovary superior; floral parts below (e.g., mustard).

• Perigynous: ovary half inferior; floral parts at rim of thalamus (e.g., rose).

• Epigynous: ovary inferior; floral parts above ovary (e.g., guava).

Memory Aids

• Hypo = below ovary; Peri = around ovary; Epi = above ovary.

• Superior ovary = hypogynous; Inferior ovary = epigynous.

Quick Checkpoints

• Identify ovary position relative to floral parts.

• Classify flowers as hypogynous, perigynous, or epigynous.

Types of Placentation

Placentation Types

• Parietal: ovules on ovary walls.

• Marginal: ovules in a single row along ovary margin.

• Axile: ovules on central column in divided ovary.

• Free central: ovules on central column in undivided ovary.

• Basal: single ovule at ovary base.

Memory Aids

• Parietal = wall; Marginal = edge; Axile = axis; Free central = free axis; Basal = base.

Quick Checkpoints

• Match placentation type with ovule arrangement.

• Identify placentation in given ovary diagrams.

Parts of Flower

Whorls and Characteristics

• Calyx: outermost whorl; sepals usually green, protect bud; gamosepalous (united) or polysepalous (free).

• Corolla: petals, usually colorful; polypetalous (free) or gamopetalous (united); shapes vary (tubular, bell, funnel, wheel).

• Androecium: stamens (male parts).

• Gynoecium: carpels (female parts).

Memory Aids

• Calyx = sepals; Corolla = petals.

• Gamosepalous = united sepals; Polysepalous = free sepals.

• Polypetalous = free petals; Gamopetalous = united petals.

Quick Checkpoints

• Identify calyx and corolla types.

• Distinguish gamosepalous vs polysepalous.

• Recognize corolla shapes and types.

Aestivation

Types and Features

• Arrangement of sepals or petals in floral bud.

• Valvate: margins touch, no overlap (e.g., Calotropis).

• Twisted: each overlaps next in one direction (e.g., China rose).

• Imbricate: margins overlap irregularly (e.g., Cassia).

• Vexillary (papilionaceous): largest petal overlaps two lateral, which overlap two anterior (e.g., pea).

Memory Aids

• Valvate = just touching.

• Twisted = spiral overlap.

• Imbricate = random overlap.

• Vexillary = butterfly-like overlap.

Quick Checkpoints

• Identify aestivation type from petal arrangement.

• Recall examples for each aestivation type.

Structure of Monocotyledonous Seed

Seed Components

• Usually endospermic; some (orchids) non-endospermic.

• Seed coat membranous, often fused with fruit wall.

• Endosperm stores food; surrounded by aleurone layer.

• Embryo small, in groove at one end of endosperm.

• Embryo parts:

  • Scutellum: large, shield-shaped cotyledon absorbing food.

  • Plumule: future shoot, enclosed in coleoptile sheath.

  • Radicle: future root, enclosed in coleorhiza sheath.

Memory Aids

• Scutellum = cotyledon for food absorption.

• Coleoptile protects plumule; coleorhiza protects radicle.

• Endosperm = food storage; aleurone layer surrounds it.

Quick Checkpoints

• Identify seed parts and their functions.

• Distinguish monocot seed features from dicot.

The Fruit

Definition and Structure

• Fruit: Mature ovary developed after fertilisation; characteristic of flowering plants.

• Parthenocarpic fruit: Fruit formed without fertilisation (e.g., banana).

• Fruit parts: Pericarp (fruit wall) and seeds.

• Pericarp types: Dry or fleshy.

• Fleshy pericarp layers: Epicarp (outer), Mesocarp (middle), Endocarp (inner).

Examples of Drupe Fruits

• Mango and coconut are drupes.

• Develop from monocarpellary superior ovary; one-seeded.

• Mango pericarp: Thin epicarp, fleshy mesocarp (edible), hard stony endocarp.

• Coconut mesocarp: Fibrous.

Memory Aids

• Fruit = Mature ovary + seeds.

• Parthenocarpic = No fertilisation (e.g., banana).

• Pericarp layers: Epi (skin), Meso (flesh), Endo (seed cover).

• Drupe = One seed + hard endocarp (e.g., mango).

Quick Checkpoints

• What is a parthenocarpic fruit?

• Name the three layers of pericarp.

• Define drupe with an example.

Fruit Classification

Types of Fruits

• Simple fruits: Develop from single ovary (mono/multicarpellary, syncarpous).

• Simple fruits divided into dry and fleshy.

• Dry fruits:

  • Dehiscent (split at maturity): Pod (pea), Follicle (delphinium), Siliqua (mustard), Silicula (iberis), Capsule (cotton).

  • Indehiscent (do not split): Cypsela (marigold), Caryopsis (maize), Achene (mirabilis), Samara (holoptelia), Nut (litchi).

  • Schizocarpic (split into one-seeded parts): Lomentum (acacia), Cremocarp (coriander), Double samara (acer), Regma (ricinus).

• Fleshy fruits: Drupe (mango), Berry (tomato), Pepo (cucurbits), Pome (pear), Hesperidium (orange), Balausta (pomegranate).

• Aggregate fruits: Develop from multicarpellary apocarpous ovary.

  • Etaerio of achenes (ranunculus)

  • Etaerio of follicles (michelia)

  • Etaerio of drupes (raspberry)

  • Etaerio of berries (custard apple)

• Composite fruits: Develop from complete inflorescence.

  • Sorosis (pineapple)

  • Syconus (banyan)

Memory Aids

• Simple = Single ovary; Dry or fleshy.

• Dry fruits: Dehiscent split open; Indehiscent do not.

• Aggregate = Multiple ovaries, separate fruits.

• Composite = From inflorescence (many flowers).

Quick Checkpoints

• Differentiate dehiscent and indehiscent dry fruits.

• Give examples of aggregate fruits.

• What is a composite fruit? Name one.

Seed Structure

Overview

• Seed develops from fertilized ovule.

• Composed of seed coat and embryo.

• Embryo includes radicle, embryonal axis, and cotyledons (one in monocots, two in dicots).

Memory Aids

• Seed = Seed coat + Embryo (radicle + axis + cotyledons).

• Dicots have two cotyledons; monocots have one.

Quick Checkpoints

• What are the main parts of a seed?

• How many cotyledons do dicots and monocots have?

Structure of Dicotyledonous Seed

Key Features

• Seed coat has two layers: outer testa and inner tegmen.

• Hilum: scar where seed attached to fruit.

• Micropyle: small pore above hilum for water entry.

• Embryo inside seed coat has two cotyledons storing food.

• Embryonal axis ends with radicle (root) and plumule (shoot).

• Endosperm present in some seeds (e.g., castor), absent in others (e.g., gram, pea) called non-endospermic.

Memory Aids

• Testa = tough outer layer; Tegmen = inner layer.

• Hilum = attachment scar; Micropyle = water entry point.

• Dicot embryo = 2 cotyledons + radicle + plumule.

• Non-endospermic seeds lack endosperm at maturity.

Quick Checkpoints

• What layers form the seed coat?

• What is the function of micropyle?

• Which parts form the embryo in dicots?

• Define non-endospermic seeds.

Structure of Monocotyledonous Seed

Key Features

• Usually endospermic; some (orchids) non-endospermic.

• Seed coat is membranous, often fused with fruit wall.

• Endosperm is large, stores food, surrounded by aleurone layer.

• Embryo small, located in groove at one end of endosperm.

• Embryo has one large shield-shaped cotyledon called scutellum.

• Embryonal axis includes plumule and radicle.

• Plumule and radicle enclosed in protective sheaths: coleoptile (plumule) and coleorhiza (radicle).

Memory Aids

• Scutellum = single cotyledon in monocots.

• Aleurone layer surrounds endosperm.

• Coleoptile protects plumule; coleorhiza protects radicle.

• Monocots usually have endosperm at maturity.

Quick Checkpoints

• What is the role of aleurone layer?

• Describe the cotyledon in monocots.

• What are coleoptile and coleorhiza?

• Are monocot seeds endospermic or non-endospermic?

Semi-technical Description of a Typical Flowering Plant

Floral Formula and Diagram

• Floral formula: Symbolic summary of flower characters.

• Floral diagram: Transverse section representation of flower parts around mother axis.

• Symbols: Br = bracteate, K = calyx, C = corolla, P = perianth, A = androecium, G = gynoecium.

• G̲ = superior ovary, G̅ = inferior ovary, ♂ = male, ♀ = female, ⚥ = bisexual.

• ⊕ = actinomorphic (radial symmetry), % = zygomorphic (bilateral symmetry).

• Fusion: Enclosed in brackets; adhesion: line above symbols.

• Floral diagram shows number, arrangement, and relation of parts; mother axis marked by a dot on top.

• Whorls arranged from outside to inside: calyx, corolla, androecium, gynoecium.

Memory Aids

• Br, K, C, P, A, G - remember flower parts order.

• G̲ (underline) = superior ovary; G̅ (overline) = inferior ovary.

• ⊕ = radial; % = bilateral symmetry.

Quick Checkpoints

• What does floral formula represent?

• How is fusion and adhesion shown?

• Order of whorls in floral diagram?

Cruciferae or Brassicaceae (Mustard Family)

Characteristics

• Distribution: Cosmopolitan, mostly temperate/cold regions.

• Vegetative: Annual/perennial herbs; taproot fleshy; stem erect, cylindrical, hairy or glabrous; leaves radical or cauline, alternate/subopposite, exstipulate, simple/rarely compound.

• Inflorescence: Racemose.

• Flower: Bisexual, actinomorphic (rarely zygomorphic), hypogynous, tetramerous.

• Calyx: 4 sepals in two whorls of 2 each, polysepalous.

• Corolla: 4 petals, polypetalous, cruciform; petals may be reduced/absent.

• Androecium: 6 stamens, tetradynamous (2 short + 4 long), dithecous, introrse.

• Gynoecium: Usually bicarpellary, syncarpous, superior ovary, unilocular, parietal placentation.

• Fruit: Siliqua, silicula, rarely lomentum.

• Seeds: Non-endospermic, often oily.

• Floral formula: ⊕ ⚥ K₂₊₂ C₄ A₂₊₄ G̲₍₂₎

Memory Aids

• Tetradynamous stamens: 2 short + 4 long.

• Cruciform corolla: 4 petals in cross shape.

• Fruit types: siliqua (long), silicula (short).

Quick Checkpoints

• What is tetradynamous condition?

• Describe placentation type in Brassicaceae.

• Identify floral formula components.

Malvaceae (Cotton Family or Mallow Family)

Characteristics

• Genera: Malva, Hibiscus, Gossypium, Sida.

• Vegetative: Annual/perennial herbs or shrubs; taproot; stem with stellate hairs; leaves simple or palmately lobed, alternate, stipulate; mucilaginous sap.

• Inflorescence: Solitary axillary or terminal.

• Flower: Hermaphrodite, actinomorphic, complete, hypogynous, pentamerous.

• Calyx: 5 sepals, free or united at base, persistent, valvate aestivation.

• Corolla: 5 petals, polypetalous, large, showy, imbricate or twisted aestivation.

• Androecium: Numerous stamens, monadelphous, epipetalous, monothecous anthers.

• Gynoecium: Bi- to multicarpellary, syncarpous, superior ovary, multilocular, ovules per locule, long style, stigmas equal to carpels.

• Fruit: Usually capsule.

• Seed: Endospermic or non-endospermic.

Memory Aids

• Stamens monadelphous (fused into one bundle).

• Leaves with stellate hairs and mucilage.

• Flower pentamerous and hypogynous.

Quick Checkpoints

• What is the androecium type in Malvaceae?

• Describe the ovary and placentation.

• Identify floral formula symbols.

Fabaceae (Papilionaceae or Pea Family)

Characteristics

• Previously subfamily Papilionoideae of Leguminosae.

• Vegetative: Trees, herbs, shrubs; taproot with root nodules; stem erect or climber; leaves alternate, pinnately compound or simple, pulvinus at base, stipulate, reticulate venation.

• Inflorescence: Racemose.

• Flower: Bisexual, zygomorphic.

• Calyx: 5 sepals, gamosepalous, valvate, imbricate aestivation.

• Corolla: 5 petals, polypetalous, papilionaceous (standard, wings, keel), vexillary aestivation.

• Androecium: 10 stamens, diadelphous (9 fused + 1 free), dithecous anthers.

• Gynoecium: Superior ovary, monocarpellary, unilocular, many ovules, single style.

• Fruit: Legume.

• Seed: One to many, non-endospermic.

• Floral formula: % ⚥ K(5) C₁₊₂₊₍₂₎ A₍₉₎₊₁ G̲₁

Memory Aids

• Diadelphous stamens: 9 + 1 arrangement.

• Papilionaceous corolla: standard, wings, keel.

• Legume fruit typical.

Quick Checkpoints

• Explain diadelphous androecium.

• Describe papilionaceous corolla parts.

• Identify floral formula components.

Compositae or Asteraceae (Sunflower Family)

Characteristics

• Largest dicot family: ~950 genera, 20,000 species.

• Vegetative: Mostly herbs, rarely shrubs/trees; taproot; stem erect/prostrate/climbing, hairy or glabrous, with latex or oil ducts; leaves alternate/rarely opposite/whorled, exstipulate, simple or compound, reticulate venation.

• Inflorescence: Head or capitulum (many sessile flowers on common receptacle).

• Florets: Two types - ray florets (outer, zygomorphic, ligulate, neuter/female) and disc florets (inner, actinomorphic, tubular).

• Heads with both types: heterogamous; with one type: homogamous (e.g., Xanthium).

• Flower: Bracteate, sessile, actinomorphic (disc) or zygomorphic (ray), bisexual or unisexual, epigynous, pentamerous.

• Calyx: 5 sepals reduced to pappus (hairs/membranes) aiding fruit dispersal.

• Corolla: 5 petals, gamopetalous; tubular in disc florets, ligulate in ray florets; valvate aestivation.

• Androecium: 5 stamens, epipetalous, syngenesious (anthers fused, filaments free).

• Gynoecium: Bicarpellary, syncarpous, inferior ovary, unilocular, basal placentation.

• Fruit: Cypsella.

• Seed: Non-endospermic.

Floral formulae

Memory Aids

• Capitulum = many florets on one receptacle.

• Ray florets: female/neuter, ligulate; disc florets: bisexual, tubular.

• Syngenesious stamens: anthers fused.

Quick Checkpoints

• Difference between ray and disc florets?

• What is pappus and its function?

• Describe floral formula symbols.

Poaceae or Gramineae

Characteristics

• Includes grains, cereals, grasses, bamboos.

• Vegetative: Annual/perennial herbs; runners, suckers, rhizomes; some shrubs.

• Root: Adventitious; stilt roots in Zea mays.

• Stem: Erect/prostrate, cylindrical, jointed (culm), hollow internodes.

• Leaves: Cauline and ramal, alternate, sessile (petiolate in bamboos), exstipulate, sheathing base, simple narrow lamina with parallel veins.

• Inflorescence: Racemose.

• Flower (floret): Zygomorphic, incomplete, perfect or unisexual (e.g., maize), hypogynous.

• Perianth: 2 or 3 small scales (lodicules), inferior.

• Androecium: 3 or 6 stamens, free in one or two whorls.

• Gynoecium: Tricarpellary, syncarpous appearing monocarpellary, superior ovary, unilocular, uniovulate, basal placentation.

• Fruit: Caryopsis.

• Seed: Endospermic, single cotyledon.

• Floral formula: Br. % ⚥ P₂ (lodicules) A₃ or 3₊₃ G̲₁

Memory Aids

• Lodicules replace perianth.

• Stem jointed with hollow internodes.

• Caryopsis fruit typical of grasses.

Quick Checkpoints

• What are lodicules?

• Describe floral formula components.

• Explain fruit type in Poaceae.

Solanaceae

Vegetative Characters

• Mostly herbs, shrubs; rarely small trees.

• Stem: herbaceous or rarely woody, erect, cylindrical, branched, solid or hollow, hairy or glabrous.

• Leaves: alternate, simple or rarely pinnately compound, without stipules; reticulate venation.

Floral Characters

• Inflorescence: solitary, axillary or cymose (e.g., Solanum).

• Flower: bisexual, actinomorphic.

• Calyx: 5 sepals, united, persistent, valvate aestivation.

• Corolla: 5 petals, united, valvate aestivation.

• Androecium: 5 stamens, epipetalous.

• Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular; placenta swollen with many ovules.

• Fruit: berry or capsule.

Memory Aids

• “5 united parts” for calyx, corolla, and stamens.

• “Bicarpellary syncarpous ovary” means two fused carpels.

• “Epipetalous stamens” attach to petals.

Quick Checkpoints

• What type of venation is present in leaves?

• Describe the aestivation of calyx and corolla.

• How many carpels form the gynoecium?

• What is the nature of the ovary?

• Identify the type of inflorescence.

Floral Formula

Explanation

• ♀ and ♂ symbols indicate bisexual flower.

• K(5): 5 sepals, united.

• C(5): 5 petals, united.

• A(5): 5 stamens.

• G(2): pistil with 2 fused carpels.

Memory Aids

• “K, C, A all 5” for sepals, petals, stamens.

• “G2” means bicarpellary gynoecium.

Quick Checkpoints

• What does K(5) represent?

• How many stamens are present?

• What is the gynoecium composition?

Economic Importance

Uses

• Food: tomato, brinjal, potato.

• Spice: chilli.

• Medicine: belladonna, ashwagandha.

• Fumigatory: tobacco.

• Ornamentals: petunia.

Memory Aids

• “Food, spice, medicine, fumigatory, ornamental” uses.

• Remember key examples for each category.

Quick Checkpoints

• Name a food crop from Solanaceae.

• Which Solanaceae plant is used as a spice?

• Give an example of medicinal Solanaceae.

• Which plant is used for fumigation?

• Name an ornamental Solanaceae plant.

Floral Diagram

Explanation

• Outer shapes: sepals protecting bud.

• Inside sepals: petals attracting pollinators.

• Stamens shown with arrows, male pollen producers.

• Center: pistil/carpel with ovary.

• Dots in center: ovules inside ovary.

• Diagram shows arrangement of flower parts.

Memory Aids

• “Sepals outside, petals inside, stamens around pistil.”

• “Dots represent ovules inside ovary.”

Quick Checkpoints

• What do outermost shapes represent?

• Where are stamens located in the diagram?

• What do the dots in the center indicate?

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