Chapter 3: Morphology of Flowering Plants

The Root

Structure and Types

• Dicots: Primary root from radicle grows into soil, forming taproot system with lateral roots (secondary, tertiary).
• Monocots: Primary root short-lived; replaced by fibrous root system from stem base.
• Adventitious roots arise from parts other than radicle (e.g., stems, leaves).
• Functions: Absorb water/minerals, anchor plant, store food, synthesize growth regulators.

Memory Aids

• Taproot = main root + branches (dicots).
• Fibrous roots = many thin roots from stem base (monocots).
• Adventitious roots = roots from non-root parts.

Quick Checkpoints

• What forms the taproot system?
• How do fibrous roots differ from taproots?
• Define adventitious roots.
• List main functions of roots.

Regions of Root

Root Tip Zones

• Root cap (calyptra): Protects root apex; 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, causing root length increase.
• Region of differentiation (maturation): Cells mature; root hairs form here to absorb water/minerals; absent in mycorrhizal roots.
• Region of mature cells: No further change; impermeable to water; anchors plant.

Memory Aids

• Root cap protects tip.
• Meristematic zone = cell division.
• Elongation zone = cell lengthening.
• Differentiation zone = cell specialization + root hairs.

Quick Checkpoints

• What is the function of the root cap?
• Where does cell division occur in root?
• Which region causes root lengthening?
• Where do root hairs develop?

Modifications of Root

Types and Functions

• Roots modify for support, storage, respiration beyond absorption.
• Storage: Swollen taproots (carrot, turnip), adventitious roots (sweet potato).
• Support: Prop roots (banyan), stilt roots (maize, sugarcane).
• Respiration: Pneumatophores (mangroves like Rhizophora, Sonneratia) grow upwards for oxygen intake.

Memory Aids

• Storage roots: carrot (conical), radish (fusiform), beetroot (napiform), sweet potato (tuberous).
• Support roots: prop and stilt roots stabilize plants.
• Pneumatophores = breathing roots in waterlogged soils.

Quick Checkpoints

• Name root types modified for storage.
• What are prop and stilt roots?
• Function of pneumatophores?

The Stem

Structure and Function

• Ascending part of axis bearing branches, leaves, flowers, and fruits.
• Develops from the plumule of the embryo in a germinating seed.
• Has nodes (where leaves attach) and internodes (regions between nodes).
• Young stems are green; mature stems often become woody and brown.
• Main functions: support branches, conduct water, minerals, and photosynthates.
• Additional roles: food storage, protection, vegetative propagation.
• Bears buds: terminal or axillary; buds are undeveloped shoots with growing points and young leaves.

Memory Aids

• Stem = Support + Transport + Storage + Protection + Propagation.
• Nodes = Leaf attachment points; Internodes = spaces between nodes.
• Buds = Young shoots with growing points.

Quick Checkpoints

• What is the origin of the stem in a seedling?
• Define nodes and internodes.
• List main functions of the stem.
• What are buds and their types?

Modifications of Stem

Types and Functions

• Underground stems store food and aid perennation (e.g., potato tuber, ginger rhizome, turmeric rhizome, zamikand, Colocasia corm).
• Rhizome: horizontal underground stem with nodes, internodes, scaly leaves, and buds (e.g., Zingiber officinale, Curcuma longa).
• Corm: unbranched, spherical, vertical underground stem for storage and vegetative 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).
• Runners: underground stems spreading to new areas, forming new plants (e.g., grass, strawberry).
• Stolons: slender lateral branches that arch down to the ground and root (e.g., mint, jasmine).
• Offsets: lateral branches with short internodes, rosette leaves, and roots in aquatic plants (e.g., Pistia, Eichhornia).
• Suckers: lateral branches from basal underground stem growing horizontally then upward (e.g., banana, pineapple, chrysanthemum).
• Thorns, spines, prickles, and bristles protect plants from animals and reduce transpiration.
• Thorns: modified stems with vascular tissue and thick bark.
• Spines: modified leaves or parts with vascular strands but no thick bark.
• Prickles: superficial outgrowths without vascular tissue, easily detached.
• Bristles: stiff hairs thickened by silica or calcium carbonate.

Memory Aids

• Rhizome = horizontal underground stem with buds and scaly leaves.
• Corm = vertical, spherical underground stem.
• Tendrils = climbing aid from axillary buds.
• Thorns = protective modified buds.
• Phylloclades and cladodes = photosynthetic stems.
• Runners and stolons = spreading stems for propagation.
• Thorns vs Spines vs Prickles vs Bristles: Stem, leaf, outgrowth, hair.

Quick Checkpoints

• What is a rhizome and examples?
• Define corm and its function.
• How do tendrils help plants?
• Difference between thorns, spines, prickles, and bristles?
• Examples of plants with phylloclades and cladodes.
• What are runners and stolons?
• Role of suckers and offsets?

The Leaf

Structure and Function

• Leaf is a lateral, flattened structure on stem nodes with 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, petiole, and lamina.
• Leaf base attaches leaf to stem; 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 holds lamina to light; flexible petioles allow leaf fluttering for cooling and air circulation.
• Lamina is the green expanded blade with veins; midrib is the central prominent vein providing support and transport.

Memory Aids

• Leaf parts: Base, Petiole, Lamina (BPL).
• Petiole flutter = leaf cooling.
• Midrib = main vein for support and transport.

Quick Checkpoints

• What is the function of the axillary bud?
• Which part of the leaf attaches it to the stem?
• How does petiole help in leaf function?
• What is the role of midrib?

Venation

Types and Characteristics

• Venation is the arrangement of veins and veinlets in the leaf lamina.
• Reticulate venation: veins form a network; typical of dicots.
• Parallel venation: veins run parallel; typical of monocots.
• Veins provide mechanical support and transport water, minerals, and food.

Memory Aids

• Reticulate = network (dicots).
• Parallel = side-by-side lines (monocots).

Quick Checkpoints

• What type of venation do dicots have?
• Which venation is found in monocots?
• How do veins support the leaf?

Types of Leaves

Simple and Compound Leaves

• Simple leaf: lamina is entire or incised but incisions do not reach midrib.
• Compound leaf: lamina incisions reach midrib, dividing into leaflets.
• Bud present in axil of petiole in both types, but not in leaflets of compound leaf.
• 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 one point at petiole tip, e.g., Bombax ceiba (silk cotton).

Memory Aids

• Simple = single lamina; Compound = multiple leaflets.
• Pinnate = feather-like; Palmate = hand-like.

Quick Checkpoints

• How to distinguish simple and compound leaves?
• What is a rachis?
• Difference between pinnate and palmate compound leaves?

Phyllotaxy

Leaf Arrangement on Stem

• Phyllotaxy is the arrangement of leaves on a stem or branch.
• Alternate: one leaf per node on 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).
• Efficient sunlight capture by leaf arrangement.

Memory Aids

• Alternate = one leaf, alternate sides.
• Opposite = two leaves, opposite sides.
• Whorled = multiple leaves in a circle.

Quick Checkpoints

• What is phyllotaxy?
• Examples of alternate and opposite phyllotaxy?
• How does whorled phyllotaxy differ?

Modifications of Leaves

Functional Adaptations

• 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: onion, garlic.
• Petiole becomes green and photosynthetic in some plants like Australian acacia.
• Insectivorous leaves: pitcher plant (Nepenthes), Venus flytrap (Dionaea).

Memory Aids

• Tendrils = climbing aid.
• Spines = defense.
• Fleshy leaves = storage.
• Insectivorous = insect-catching.

Quick Checkpoints

• What are leaf modifications?
• Examples of leaves modified for climbing and defense?
• Which plants have fleshy storage leaves?
• How do insectivorous leaves function?

Inflorescence

Concept and Types

• A flower is a modified shoot where the shoot apical meristem becomes floral meristem.
• Inflorescence is the arrangement of flowers on the floral axis.
• Two main types: Racemose and Cymose.
• In Racemose, the main axis grows continuously; flowers develop laterally in acropetal succession (younger flowers at the top).
• In Cymose, the main axis ends in a flower, limiting growth; flowers develop in basipetal order (older flowers at the top or center).

Memory Aids

• Racemose: "R" for "Run" (main axis keeps growing).
• Cymose: "C" for "Cease" (main axis stops at flower).
• Acropetal succession: younger flowers at the apex.
• Basipetal order: older flowers at the apex.

Quick Checkpoints

• What changes in the shoot apical meristem to form a flower?
• Define inflorescence.
• Distinguish between racemose and cymose inflorescence based on growth and flower order.
• What is acropetal succession?
• What is basipetal order?

Special Types of Inflorescence

Examples and Features

• Hypanthodium: Fleshy receptacle forming a hollow structure with an apical opening guarded by scales; e.g., Ficus religiosa (peepal), Ficus benghalensis (banyan).
• Verticillaster: Modified condensed dichasial cyme with two whorls of 3 to 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 house" with guarded opening.
• Verticillaster: "Whorled clusters" on nodes.
• Cyathium: "Cup flower" with many males around one female.

Quick Checkpoints

• What is the structure of hypanthodium?
• How are flowers arranged in verticillaster?
• Describe the composition of cyathium inflorescence.

The Flower

Subtopics

• Unit of sexual reproduction in angiosperms.
• Four whorls: calyx, corolla, androecium, gynoecium on thalamus (receptacle).
• Calyx and corolla are accessory; androecium and gynoecium are reproductive.
• Perianth: when calyx and corolla are indistinct (e.g., lily).
• Bisexual flower: has both androecium and gynoecium; unisexual: only one.
• Complete flower: all four whorls present; incomplete: any whorl absent.
• Symmetry: actinomorphic (radial), zygomorphic (bilateral), asymmetric (irregular).
• Floral appendages in multiples: trimerous (3), tetramerous (4), pentamerous (5).
• Bracteate flowers have bracts at pedicel base; ebracteate lack bracts.

Memory Aids

• Perianth = Calyx + Corolla indistinct.
• Bisexual = Both reproductive whorls present.
• Actinomorphic = Radial symmetry; Zygomorphic = Bilateral symmetry.
• Trimerous, Tetramerous, Pentamerous = Floral parts in multiples of 3, 4, 5.

Quick Checkpoints

• What are the four floral whorls?
• Define bisexual and unisexual flowers.
• What is perianth?
• How to identify actinomorphic vs zygomorphic flowers?
• What does complete flower mean?

Flower Types Based on Ovary Position

Subtopics

• Hypogynous: floral parts below ovary; ovary superior (e.g., mustard, China rose).
• Perigynous: floral parts around ovary on cup-shaped thalamus; ovary half-inferior (e.g., rose, plum).
• Epigynous: floral parts above ovary; ovary inferior (e.g., guava, cucumber, sunflower ray florets).

Memory Aids

• Hypogynous = "Hypo" means below; ovary on top.
• Perigynous = "Peri" means around; ovary in middle.
• Epigynous = "Epi" means above; ovary below.

Quick Checkpoints

• Where are floral parts attached in hypogynous flowers?
• What is the ovary position in perigynous flowers?
• Which flowers have inferior ovary?

Types of Placentation

Subtopics

• Parietal: seeds on ovary walls.
• Marginal: seeds in single row along ovary edge.
• Axile: seeds on central column in divided ovary.
• Free central: seeds around central column in undivided ovary.
• Basal: single seed at ovary base.

Memory Aids

• Parietal = "Pari" means wall.
• Marginal = seeds on margin edge.
• Axile = Axis center.
• Free central = Central column free in ovary.
• Basal = Base seed.

Quick Checkpoints

• Where are seeds located in axile placentation?
• Define free central placentation.
• Which placentation has single seed?

Parts of Flower

Subtopics

• Calyx: outermost whorl; sepals protect bud; gamosepalous (united) or polysepalous (free).
• Corolla: petals attract pollinators; polypetalous (free) or gamopetalous (united); shapes vary.

Memory Aids

• Sepals = Calyx; Petals = Corolla.
• Gamosepalous = united sepals; Polysepalous = free sepals.
• Polypetalous = free petals; Gamopetalous = united petals.

Quick Checkpoints

• What is the function of sepals?
• Difference between gamosepalous and polysepalous calyx?
• What shapes can corolla have?

Aestivation

Subtopics

• Arrangement of sepals or petals in floral bud.
• Main types: valvate, twisted, imbricate, vexillary (papilionaceous).
• Valvate: margins touch, no overlap (e.g., Calotropis).
• Twisted: each overlaps next in spiral (e.g., China rose).
• Imbricate: margins overlap irregularly (e.g., Cassia).
• Vexillary: largest petal overlaps others; typical in pea family.

Memory Aids

• Valvate = just touching edges.
• Twisted = spiral overlap.
• Imbricate = random overlap.
• Vexillary = largest petal covers others.

Quick Checkpoints

• What is aestivation?
• Identify valvate and twisted aestivation.
• Which aestivation is typical of pea flowers?

Structure of Monocotyledonous Seed

Subtopics

• Mostly endospermic; some non-endospermic (e.g., orchids).
• Seed coat membranous, often fused with fruit wall.
• Endosperm stores food; surrounded by aleurone layer.
• Embryo small, in groove at end of endosperm.
• Embryo parts: scutellum (absorbs food), plumule (shoot), radicle (root).
• Protective sheaths: coleoptile (plumule), coleorhiza (radicle).

Memory Aids

• Scutellum = shield-shaped cotyledon.
• Coleoptile protects plumule; Coleorhiza protects radicle.
• Aleurone layer surrounds endosperm.

Quick Checkpoints

• What is the function of aleurone layer?
• Identify parts of monocot embryo.
• Difference between coleoptile and coleorhiza.

The Fruit

Definition and Structure

• Fruit is a mature ovary developed after fertilisation in flowering plants.
• Parthenocarpic fruit forms without fertilisation, e.g., banana.
• Fruit consists of pericarp (fruit wall) and seeds.
• Pericarp may be dry or fleshy; fleshy pericarp has three layers: epicarp (outer), mesocarp (middle), endocarp (inner).

Examples of Drupe

• Mango and coconut are drupes, developing from monocarpellary superior ovaries.
• Mango pericarp: thin epicarp, fleshy mesocarp (edible), hard stony endocarp.
• Coconut mesocarp is fibrous.

Memory Aids

• Fruit = Mature ovary + seeds.
• Parthenocarpic = No fertilisation (banana).
• Pericarp layers: Epicarp (skin), Mesocarp (flesh), Endocarp (seed cover).
• Drupe = One seed, hard endocarp (mango, coconut).

Quick Checkpoints

• What is a parthenocarpic fruit?
• Name the three layers of pericarp.
• Which fruits are classified as drupes?

Fruit Classification

Simple Fruits

• Develop from mono- or multicarpellary syncarpous ovary.
• Divided into dry and fleshy fruits.
• Dry fruits:
  • Dehiscent: Pod (pea), Follicle (Delphinium), Siliqua (mustard), Silicula (Iberis), Capsule (cotton).
  • Indehiscent: Cypsela (marigold), Caryopsis (maize), Achene (Mirabilis), Samara (Holoptelia), Nut (litchi).
  • Schizocarpic: 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.
• Types:
  • Etaerio of achenes (e.g., Ranunculus).
  • Etaerio of follicles (e.g., Michelia).
  • Etaerio of drupes (e.g., raspberry).
  • Etaerio of berries (e.g., custard apple).

Composite Fruits

• Develop from complete inflorescence.
• Examples: Sorosis (pineapple), Syconus (banyan).

Memory Aids

• Simple fruits = Single ovary; dry or fleshy.
• Aggregate fruits = Multiple ovaries, separate carpels.
• Composite fruits = Whole inflorescence forms fruit.
• Dehiscent dry fruits split open; indehiscent do not.

Quick Checkpoints

• What defines a simple fruit?
• Give examples of dehiscent and indehiscent dry fruits.
• How do aggregate fruits develop?
• What are composite fruits?

The Seed

Overview

• Ovules develop into seeds after fertilisation.
• Seed consists of seed coat and embryo.
• Embryo has radicle, embryonal axis, and cotyledons (one in monocots like wheat, maize; two in dicots like gram, pea).

Memory Aids

• Seed = Seed coat + Embryo (radicle + axis + cotyledons).
• Monocot = 1 cotyledon; Dicot = 2 cotyledons.

Quick Checkpoints

• What are the main parts of a seed?
• Difference between monocot and dicot embryos?

Structure of Dicotyledonous Seed

Seed Coat and Embryo

• 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 embryonal axis and two cotyledons storing food.
• Embryonal axis ends: radicle (root) and plumule (shoot).
• Endosperm present in some seeds (e.g., castor) as food storage.
• Non-endospermic seeds (e.g., gram, pea) lack endosperm at maturity.

Memory Aids

• Testa = outer seed coat; Tegmen = inner seed coat.
• Hilum = seed attachment scar; Micropyle = water entry pore.
• Radicle = root; Plumule = shoot.
• Dicot seeds usually non-endospermic.

Quick Checkpoints

• What layers form the seed coat?
• Function of micropyle and hilum?
• Difference between endospermic and non-endospermic seeds?

Structure of Monocotyledonous Seed

Seed Components

• Monocot seeds mostly 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, in groove at one end of endosperm.
• Embryo has one large shield-shaped cotyledon called scutellum.
• Embryonal axis has plumule (shoot) and radicle (root).
• Plumule and radicle enclosed in sheaths: coleoptile (shoot sheath) and coleorhiza (root sheath).

Memory Aids

• Aleurone layer surrounds endosperm.
• Scutellum = single cotyledon in monocots.
• Coleoptile protects plumule; Coleorhiza protects radicle.
• Monocot seeds usually endospermic.

Quick Checkpoints

• What is the role of aleurone layer?
• Identify parts of monocot embryo.
• Difference between coleoptile and coleorhiza?

Semi-technical Description of a Typical Flowering Plant

Floral Formula and Diagram

• Floral formula summarizes floral characters using symbols.
• Floral diagram shows arrangement of flower parts from a transverse section of flower bud.
• Symbols: Br = bracteate, K = calyx, C = corolla, P = perianth, A = androecium, G = gynoecium.
• G̲ = superior ovary, G̅ = inferior ovary.
• ♂ = male, ♀ = female, ⚥ = bisexual.
• ⊕ = actinomorphic, % = zygomorphic flower.
• Fusion shown by brackets; adhesion by line above symbols.
• Floral diagram shows number, arrangement, and relation of parts; mother axis marked by a dot on top.
• Whorls drawn from outside to inside: calyx, corolla, androecium, gynoecium.
• Example: Brassicaceae floral formula ⊕ ⚥ K₂₊₂ C₄ A₂₊₄ G̲₍₂₎.

Memory Aids

• Br = Bract, K = Calyx, C = Corolla, A = Androecium, G = Gynoecium.
• G̲ = Superior ovary, G̅ = Inferior ovary.
• ⊕ = Radial symmetry, % = Bilateral symmetry.
• Fusion = brackets, Adhesion = line above.

Quick Checkpoints

• What does the floral formula represent?
• How is fusion and adhesion shown in floral formula?
• What information does a floral diagram provide?
• Identify symbols for ovary position and flower sexuality.

Cruciferae or Brassicaceae (Mustard Family)

Characteristics

• Distribution: Cosmopolitan, mostly temperate/cold regions.
• Vegetative: Annual/perennial herbs; taproot fleshy; erect cylindrical stem; leaves radical or cauline, alternate/subopposite, exstipulate, simple or 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 separate petals in cross shape.
• Parietal placentation = ovules on ovary wall.

Quick Checkpoints

• What is the stamen arrangement in Brassicaceae?
• Describe the ovary position and placentation.
• What type of inflorescence is present?
• Identify the floral formula symbols for this family.

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, anthers monothecous.
• 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 fused into a tube (monadelphous).
• Leaves with stellate hairs and mucilage.
• Valvate calyx and showy petals.

Quick Checkpoints

• What type of stamen arrangement is typical?
• Describe the ovary and placentation.
• What is the common fruit type?
• Identify key vegetative features.

Fabaceae (Papilionaceae or Pea Family)

Characteristics

• Previously subfamily Papilionoideae of Leguminosae.
• Vegetative: Trees, herbs, shrubs; taproot with root nodules; erect or climbing stem; 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), anthers dithecous.
• Gynoecium: Superior ovary, monocarpellary, unilocular, many ovules, single style.
• Fruit: Legume.
• Seed: One to many, non-endospermic.
• Floral formula: % ⚥ K(5) C_1+2+(2) A₍₉₎₊₁ G̲₁.

Memory Aids

• Diadelphous stamens = 9 fused + 1 free.
• Papilionaceous corolla = butterfly-shaped petals.
• Legume fruit = pod splitting on two sides.

Quick Checkpoints

• What is the stamen arrangement in Fabaceae?
• Describe the corolla structure.
• What type of fruit is produced?
• Identify the floral formula symbols.

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, latex tubes 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 (zygomorphic, ligulate, neuter/female) and disc florets (actinomorphic, tubular).
• Heads with two floret types are heterogamous; Xanthium has homogamous heads.
• 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 (disc) or ligulate (ray), valvate aestivation.
• Androecium: 5 stamens, epipetalous, syngenesious (anthers fused, filaments free).
• Gynoecium: Bicarpellary, syncarpous, inferior ovary, unilocular, basal placentation.
• Fruit: Cypsella.
• Seed: Non-endospermic.

Memory Aids

• Capitulum = many sessile flowers on one receptacle.
• Ray florets = female or neuter, zygomorphic.
• Disc florets = bisexual, actinomorphic.
• Pappus aids seed dispersal.

Quick Checkpoints

• What are the two types of florets in Asteraceae?
• Describe the calyx modification.
• What is the placentation type?
• Identify floral formula symbols for ray and disc florets.

Poaceae or Gramineae

Characteristics

• Famous for grains, cereals, grasses, and bamboos.
• Vegetative: Annual or perennial herbs; some shrubs; adventitious roots; stilt roots in maize; erect/prostrate, cylindrical, jointed stem (culm) with hollow internodes.
• Leaves: Cauline and ramal, alternate, sessile (petiolate in bamboos), exstipulate, sheathing base, simple long narrow lamina with parallel veins.
• Inflorescence: Racemose.
• Flower: Zygomorphic, incomplete, perfect or unisexual (e.g., maize), hypogynous.
• Perianth: 2 or 3 small scales called lodicules, inferior.
• Androecium: 3 or 6 free stamens in one or two whorls.
• Gynoecium: Tricarpellary, syncarpous appearing monocarpellary, superior ovary, unilocular, uniovulate, basal placentation.
• Fruit: Caryopsis.
• Seed: Endospermic with single cotyledon.
• Floral formula: Br. % ⚥ P₂ (lodicules) A₃ or 3₊₃ G̲₁.

Memory Aids

• Lodicules replace perianth.
• Stem jointed with hollow internodes.
• Fruit is caryopsis (grain).

Quick Checkpoints

• What replaces the perianth in Poaceae flowers?
• Describe the stem and root types.
• What is the ovary and placentation type?
• Identify the floral formula symbols.

Solanaceae

Vegetative characters

• Plants mostly herbs, shrubs, rarely small trees.
• Stem: herbaceous (rarely woody), aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous.
• Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate.

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" pattern: calyx, corolla, stamens all in fives and united.
• Flower is bisexual and actinomorphic (radial symmetry).
• Ovary is superior and bilocular with many ovules.

Quick Checkpoints

• What type of plants are common in Solanaceae?
• Describe the aestivation type in calyx and corolla.
• How many carpels form the gynoecium?
• What is the nature of the ovary and fruit?

Floral Formula

Explanation

• ♀ symbol: female flower; ♂ symbol: male flower.
• K(5): 5 sepals.
• C(5): 5 petals.
• A(5): 5 stamens.
• G(2): pistil with 2 fused carpels.
• Indicates bisexual flower with 5 sepals, 5 petals, 5 stamens, and bicarpellary pistil.

Memory Aids

• Remember K, C, A, G stand for calyx, corolla, androecium, gynoecium.
• Numbers in parentheses indicate number of parts.
• Bisexual flower shown by presence of both male and female symbols.

Quick Checkpoints

• What does K(5) represent?
• How many stamens are present?
• What does G(2) indicate about carpels?
• What symbols show flower sexuality?

Economic Importance

Uses

• Food: tomato, brinjal, potato.
• Spice: chilli.
• Medicine: belladonna, ashwagandha.
• Fumigatory: tobacco.
• Ornamentals: petunia.

Memory Aids

• Food plants include common vegetables.
• Chilli is a major spice source.
• Medicinal plants include belladonna and ashwagandha.
• Tobacco used for fumigation.
• Petunia is ornamental.

Quick Checkpoints

• Name food plants from Solanaceae.
• Which plant is used as a spice?
• List medicinal plants in this family.
• What is the fumigatory plant?
• Which plant is ornamental?

Floral Diagram

Explanation

• Outer shapes: sepals protecting flower bud.
• Inside sepals: petals, colorful to attract pollinators.
• Stamens shown with arrows, male pollen-producing parts.
• Center: pistil/carpel with ovary.
• Dots in center represent ovules inside ovary.
• Diagram shows arrangement of flower parts visually.

Memory Aids

• Sepals outermost, petals inside sepals.
• Stamens surround central pistil.
• Ovules shown as dots inside ovary.
• Diagram helps visualize flower structure.

Quick Checkpoints

• What do outermost shapes represent?
• Where are petals located?
• What do arrows indicate?
• What do dots in center represent?
• What is the central part of the flower?