Class 11 Biology Notes Chapter 5 (Chapter 5) – Examplar Problems (English) Book

Alright class, let's delve into Chapter 5: Morphology of Flowering Plants. This is a foundational chapter, crucial for understanding plant diversity and classification, and frequently tested in various government exams. Pay close attention to the terminology and examples.

Chapter 5: Morphology of Flowering Plants - Detailed Notes

Introduction:
Morphology deals with the study of the external form, structure, and relative position of different organs of an organism. In flowering plants (Angiosperms), the main parts are the root system (underground) and the shoot system (aerial).

1. The Root System

• Primary Functions: Anchorage, absorption of water and minerals, storage of reserve food material, synthesis of plant growth regulators.
• Parts of a Root:
  • Root Cap: Thimble-like structure protecting the tender apex (root apical meristem). Secretes mucilage for lubrication. In aquatic plants (Pistia, Eichhornia), root pockets are present instead.
  • Region of Meristematic Activity: Small region of actively dividing cells just above the root cap. Cells are small, thin-walled with dense protoplasm.
  • Region of Elongation: Proximal to the meristematic zone. Cells undergo rapid elongation and enlargement, responsible for root growth in length.
  • Region of Maturation: Proximal to the elongation zone. Cells differentiate and mature. Root hairs (unicellular epidermal extensions) arise from this region, increasing surface area for absorption.
• Types of Root Systems:
  • Tap Root System: Primary root (direct elongation of radicle) grows deep and bears lateral roots of several orders (secondary, tertiary). Seen in dicotyledons (e.g., Mustard, Gram, Mango).
  • Fibrous Root System: Primary root is short-lived and replaced by numerous thin, fibre-like roots originating from the base of the stem. Seen in monocotyledons (e.g., Wheat, Rice, Grass).
  • Adventitious Root System: Roots arise from parts of the plant other than the radicle (e.g., stem base, nodes, leaves). Seen in Grass, Monstera, Banyan tree.
• Modifications of Roots: Roots modify to perform functions other than absorption and anchorage.
  • For Storage:
    • Tap roots: Carrot (conical), Turnip (napiform), Radish (fusiform).
    • Adventitious roots: Sweet Potato (tuberous roots), Asparagus (fasciculated roots).
  • For Support:
    • Prop Roots: Hanging roots arising from branches, grow downwards to provide support (e.g., Banyan tree - Ficus benghalensis).
    • Stilt Roots: Supporting roots arising from lower nodes of the stem (e.g., Maize, Sugarcane, Pandanus).
  • For Respiration (Pneumatophores): Roots grow vertically upwards (negatively geotropic) from waterlogged soil to get oxygen for respiration. Have pores called lenticels. (e.g., Rhizophora - grows in swampy/mangrove areas).

2. The Stem

• Characteristics: Ascending part of the axis bearing branches, leaves, flowers, and fruits. Develops from the plumule. Differentiated into nodes (regions where leaves arise) and internodes (portion between two nodes). Bears buds (axillary or terminal). Generally positively phototropic and negatively geotropic.
• Primary Functions: Spreading out branches, bearing leaves, flowers, fruits; conduction of water, minerals, and photosynthates; some stems perform storage, support, protection, vegetative propagation.
• Modifications of Stems:
  • Underground Stems (for storage & perennation):
    • Rhizome: Thickened, horizontal, dorsiventral stem with nodes, internodes, scale leaves, buds (e.g., Ginger, Turmeric, Ferns).
    • Corm: Condensed, vertically growing, spherical/subspherical stem with nodes, internodes, buds (e.g., Zaminkand, Colocasia, Crocus, Gladiolus).
    • Tuber: Swollen tip of an underground lateral stem (stolon) bearing 'eyes' (nodes with buds) (e.g., Potato).
    • Bulb: Reduced, disc-like stem with fleshy scale leaves storing food (e.g., Onion, Garlic).
  • Sub-aerial Stems (for vegetative propagation):
    • Runner: Slender, horizontal branch creeping on the ground, rooting at nodes (e.g., Grasses, Oxalis).
    • Stolon: Slender lateral branch arising from the base of the main axis, arches downwards to touch the ground and form a new plant (e.g., Mint, Jasmine).
    • Offset: Like a runner but shorter, thicker, and found in aquatic plants; one internode long (e.g., Pistia, Eichhornia).
    • Sucker: Lateral branch arising from the basal underground part of the main stem, grows horizontally beneath the soil then obliquely upwards (e.g., Banana, Pineapple, Chrysanthemum).
  • Aerial Stem Modifications:
    • Stem Tendrils: Thread-like, coiled structures developed from axillary buds for climbing (e.g., Gourds - cucumber, pumpkins, watermelon; Grapevines).
    • Thorns: Hard, pointed structures developed from axillary buds for protection from browsing animals (e.g., Citrus, Bougainvillea).
    • Phylloclade: Flattened (e.g., Opuntia) or cylindrical (e.g., Euphorbia) green stem performing photosynthesis; leaves reduced to spines. Found in xerophytes. Unlimited growth.
    • Cladode: Green stem modification similar to phylloclade but usually of one or two internodes only; limited growth (e.g., Asparagus, Ruscus).

3. The Leaf

• Characteristics: Lateral, generally flattened structure borne on the stem at the node. Develops from shoot apical meristem. Acropetal arrangement. Most important vegetative organ for photosynthesis. Has a bud in its axil (axillary bud).
• Parts of a Leaf:
  • Leaf Base: Attaches leaf to stem. May bear two lateral small leaf-like structures called stipules (stipulate/exstipulate leaf). In monocots, leaf base expands into a sheath covering the stem partially or wholly (sheathing leaf base). In some legumes, leaf base may become swollen (pulvinus) - responsible for sleep movements.
  • Petiole: Stalk connecting lamina to leaf base. Allows lamina to flutter in wind (cooling, bringing fresh air).
  • Lamina (Leaf Blade): Green, expanded part with veins and veinlets. Shape, margin, apex, surface vary. Midrib is the prominent central vein.
• Venation: Arrangement of veins and veinlets in the lamina.
  • Reticulate Venation: Veinlets form a network. Characteristic of dicotyledons (e.g., Mango, Peepal). Exception: Calophyllum.
  • Parallel Venation: Veins run parallel to each other within the lamina. Characteristic of monocotyledons (e.g., Grass, Banana). Exception: Smilax.
• Types of Leaves:
  • Simple Leaf: Lamina is entire or incised, but incisions do not touch the midrib.
  • Compound Leaf: Incisions of the lamina reach up to the midrib (rachis) or petiole base, breaking it into leaflets.
    • Pinnately Compound: Leaflets present on a common axis, the rachis (represents midrib). E.g., Neem.
    • Palmately Compound: Leaflets attached at a common point (tip of petiole). E.g., Silk Cotton (Bombax).
• Phyllotaxy: Pattern of arrangement of leaves on the stem or branch.
  • Alternate: Single leaf arises at each node in an alternate manner (e.g., China rose, Mustard, Sunflower).
  • Opposite: Pair of leaves arise at each node, opposite to each other (e.g., Calotropis, Guava).
  • Whorled: More than two leaves arise at a node and form a whorl (e.g., Alstonia, Nerium).
• Modifications of Leaves:
  • Tendrils: For climbing (e.g., Peas - leaflets modified).
  • Spines: For defence (e.g., Cacti - entire leaf modified; Acacia - stipules modified).
  • Storage Leaves: Fleshy leaves store food (e.g., Onion, Garlic).
  • Pitcher: Lamina modified into a pitcher to trap insects (e.g., Pitcher plant - Nepenthes).
  • Bladder: Leaf segments modified into bladders to trap insects (e.g., Bladderwort - Utricularia).
  • Phyllode: Petiole becomes flattened, green, and performs photosynthesis when lamina is reduced (e.g., Australian Acacia).

4. The Inflorescence

• Definition: Arrangement of flowers on the floral axis (peduncle).
• Types:
  • Racemose: Main axis continues to grow; flowers borne laterally in acropetal succession (older flowers at base, younger at apex). Indefinite growth. (e.g., Mustard, Radish).
  • Cymose: Main axis terminates in a flower, hence limited growth. Flowers borne in basipetal succession (older flower at apex, younger below). (e.g., Jasmine, Calotropis, Bougainvillea).

5. The Flower

• Definition: Modified shoot wherein the shoot apical meristem changes to floral meristem. Internodes do not elongate, axis gets condensed. Reproductive unit in angiosperms.
• Parts: Arranged in whorls on the swollen end of the stalk (pedicel) called thalamus or receptacle.
  • Calyx: Outermost whorl, composed of sepals. Usually green, protective in bud stage. Gamosepalous (sepals united), Polysepalous (sepals free).
  • Corolla: Composed of petals. Usually brightly coloured to attract pollinators. Gamopetalous (petals united), Polypetalous (petals free). Shape varies (tubular, bell-shaped, funnel-shaped, wheel-shaped).
  • Perianth: When calyx and corolla are not distinct (e.g., Lily). Composed of tepals. Petaloid (coloured) or Sepaloid (green).
  • Androecium: Composed of stamens (male reproductive organ). Each stamen consists of filament (stalk) and anther (bilobed structure containing pollen sacs). Sterile stamen is called staminode.
    • Epipetalous: Stamens attached to petals (e.g., Brinjal).
    • Epiphyllous: Stamens attached to perianth (e.g., Lily).
    • Cohesion: Stamens may be united: Monadelphous (one bundle, e.g., China rose), Diadelphous (two bundles, e.g., Pea), Polyadelphous (more than two bundles, e.g., Citrus).
    • Variation in filament length within a flower (e.g., Salvia, Mustard).
  • Gynoecium (Pistil): Female reproductive part, composed of one or more carpels. Each carpel has three parts: Stigma (receptive tip for pollen), Style (connects stigma to ovary), Ovary (enlarged basal part containing ovules).
    • Apocarpous: More than one carpel, free (e.g., Lotus, Rose).
    • Syncarpous: More than one carpel, fused (e.g., Mustard, Tomato).
    • Ovary Position (based on position relative to other floral parts on thalamus):
      • Hypogynous Flower: Gynoecium occupies the highest position; other parts below it. Ovary is Superior (e.g., Mustard, China rose, Brinjal).
      • Perigynous Flower: Gynoecium in the centre; other parts on the rim of the thalamus almost at the same level. Ovary is Half-inferior (e.g., Plum, Rose, Peach).
      • Epigynous Flower: Margin of thalamus grows upward enclosing the ovary completely and getting fused with it; other parts arise above the ovary. Ovary is Inferior (e.g., Guava, Cucumber, Ray florets of Sunflower).
• Symmetry:
  • Actinomorphic (Radial): Can be divided into two equal radial halves in any radial plane passing through the centre (e.g., Mustard, Datura, Chilli).
  • Zygomorphic (Bilateral): Can be divided into two similar halves only in one particular vertical plane (e.g., Pea, Gulmohur, Bean, Cassia).
• Floral Appendages:
  • Trimerous: Floral appendages in multiples of 3 (Monocots).
  • Tetramerous: Floral appendages in multiples of 4.
  • Pentamerous: Floral appendages in multiples of 5 (Dicots).
• Bracts: Reduced leaf found at the base of the pedicel. Bracteate (with bracts), Ebracteate (without bracts).
• Aestivation: Mode of arrangement of sepals or petals in floral bud with respect to other members of the same whorl.
  • Valvate: Sepals/petals just touch each other at the margin without overlapping (e.g., Calotropis).
  • Twisted: One margin overlaps the next one, and so on (e.g., China rose, Lady's finger, Cotton).
  • Imbricate: Margins overlap one another but not in any particular direction (e.g., Cassia, Gulmohur).
  • Vexillary (Papilionaceous): In Pea, Bean flowers. Five petals; largest (standard) overlaps two lateral petals (wings), which in turn overlap the two smallest anterior petals (keel).
• Placentation: Arrangement of ovules within the ovary.
  • Marginal: Placenta forms a ridge along the ventral suture of the ovary; ovules borne in two rows (e.g., Pea - monocarpellary ovary).
  • Axile: Placenta is axial; ovules attached to it in a multilocular ovary (e.g., China rose, Tomato, Lemon - syncarpous ovary).
  • Parietal: Ovules develop on the inner wall of the ovary or on peripheral part. Ovary one-chambered but becomes two-chambered due to formation of a false septum (replum) (e.g., Mustard, Argemone).
  • Free Central: Ovules borne on central axis; septa absent (e.g., Dianthus, Primrose - syncarpous ovary).
  • Basal: Placenta develops at the base of the ovary; single ovule attached (e.g., Sunflower, Marigold - syncarpous ovary).

6. The Fruit

• Definition: Mature or ripened ovary, developed after fertilisation. If formed without fertilisation, it's parthenocarpic (e.g., Banana).
• Parts:
  • Pericarp (Fruit Wall): Develops from ovary wall. Differentiated into outer Epicarp, middle Mesocarp, inner Endocarp. Can be dry or fleshy.
  • Seed(s): Develop from ovules.
• Types: (Focus on NCERT examples)
  • Simple Fruits: Develop from monocarpellary or multicarpellary syncarpous ovary.
    • Fleshy Fruits: Pericarp is fleshy.
      • Drupe: Develops from monocarpellary superior ovary. One-seeded. Pericarp differentiated. Endocarp is hard and stony. (e.g., Mango - mesocarp edible; Coconut - mesocarp fibrous).
      • Berry: Develops from multicarpellary syncarpous ovary. Pericarp fleshy, no hard endocarp. Seeds embedded in pulp. (e.g., Tomato, Guava, Grapes).
    • Dry Fruits: Pericarp is dry. (e.g., Legume - Pea; Capsule - Cotton, Datura; Caryopsis - Maize/Wheat).
  • Aggregate Fruits: Develop from multicarpellary apocarpous ovary (e.g., Strawberry, Raspberry).
  • Composite Fruits: Develop from entire inflorescence (e.g., Pineapple, Fig, Mulberry).

7. The Seed

• Definition: Fertilised ovule. Consists of seed coat(s) and an embryo.
• Embryo: Consists of an embryonal axis and one (monocot) or two (dicot) cotyledons.
• Seed Coat: Outer protective layer(s). Develops from integuments of ovule. Usually two layers: outer Testa, inner Tegmen. Hilum (scar where seed was attached to fruit), Micropyle (small pore near hilum).
• Endosperm: Food storing tissue formed during double fertilisation. May persist in mature seed (Endospermic/Albuminous, e.g., Castor, Maize, Wheat) or be consumed during development (Non-endospermic/Exalbuminous, e.g., Pea, Bean, Gram).
• Structure of Dicot Seed (e.g., Bean, Gram):
  • Seed coat.
  • Embryo: Embryonal axis (Tigellum) + two fleshy cotyledons (store food). Axis has Plumule (future shoot) and Radicle (future root).
• Structure of Monocot Seed (e.g., Maize):
  • Seed coat fused with fruit wall (pericarp).
  • Endosperm: Bulky, stores food. Separated from embryo by proteinaceous Aleurone layer.
  • Embryo: Small, situated in a groove at one end of endosperm. Consists of one large, shield-shaped cotyledon (Scutellum), and a short axis with Plumule and Radicle. Plumule enclosed in Coleoptile, Radicle enclosed in Coleorhiza.

8. Floral Formula and Floral Diagram

• Floral Formula: Symbolic representation of floral characters. Symbols used:
  • Br (Bracteate), Ebr (Ebracteate)
  • ⊕ (Actinomorphic), % (Zygomorphic)
  • ⚥ (Bisexual), ♂ (Male), ♀ (Female)
  • K (Calyx), C (Corolla), P (Perianth), A (Androecium), G (Gynoecium)
  • Number of parts indicated by numeral after symbol. () indicates fusion. ⌒ indicates adhesion.
  • G̱ (Superior ovary), G̅ (Inferior ovary), G- (Half-inferior ovary).
• Floral Diagram: Provides information about the number of parts, arrangement, and relation with one another. Position of mother axis indicated by a dot/circle at the top.

9. Description of Important Families

• Fabaceae (Subfamily: Papilionoideae; earlier Leguminosae):
  • Habit: Trees, shrubs, herbs; root nodules common.
  • Stem: Erect or climber.
  • Leaves: Alternate, pinnately compound or simple; leaf base pulvinate; stipulate; reticulate venation.
  • Inflorescence: Racemose.
  • Flower: Bisexual, zygomorphic (%).
  • Calyx: K(5), gamosepalous; valvate/imbricate aestivation.
  • Corolla: C1+2+(2), polypetalous, papilionaceous (vexillary aestivation).
  • Androecium: A(9)+1, diadelphous, anther dithecous.
  • Gynoecium: G̱1, monocarpellary, unilocular, superior ovary, marginal placentation.
  • Fruit: Legume. Seed: one to many, non-endospermic.
  • Floral Formula: % ⚥ K(5) C1+2+(2) A(9)+1 G̱1
  • Economic Importance: Pulses (Gram, Arhar, Pea), Edible oil (Soybean, Groundnut), Dye (Indigofera), Fibres (Sunhemp), Fodder (Sesbania, Trifolium), Ornamentals (Lupin, Sweet pea), Medicine (Muliathi).
• Solanaceae (Potato family):
  • Habit: Mostly herbs, shrubs, rarely small trees.
  • Stem: Herbaceous rarely woody; aerial erect, cylindrical, branched, solid/hollow, hairy/glabrous, underground stem in potato.
  • Leaves: Alternate, simple, rarely pinnately compound; exstipulate; reticulate venation.
  • Inflorescence: Solitary, axillary or cymose (as in Solanum).
  • Flower: Bisexual, actinomorphic (⊕).
  • Calyx: K(5), gamosepalous, persistent, valvate aestivation.
  • Corolla: C(5), gamopetalous; valvate aestivation.
  • Androecium: A5, epipetalous.
  • Gynoecium: G̱(2), bicarpellary syncarpous; superior ovary, bilocular, placenta swollen with many ovules, axile placentation.
  • Fruit: Berry or capsule. Seed: many, endospermic.
  • Floral Formula: ⊕ ⚥ K(5) C(5) A5 G̱(2)
  • Economic Importance: Food (Tomato, Brinjal, Potato), Spice (Chilli), Medicine (Belladonna, Ashwagandha), Fumigatory (Tobacco), Ornamentals (Petunia).
• Liliaceae (Lily family): Monocot family.
  • Habit: Perennial herbs with underground bulbs/corms/rhizomes.
  • Leaves: Mostly basal, alternate, linear, exstipulate; parallel venation.
  • Inflorescence: Solitary / cymose; often umbellate clusters.
  • Flower: Bisexual, actinomorphic (⊕).
  • Perianth: P(3+3), tepals 6, often united into tube; valvate aestivation.
  • Androecium: A3+3, epiphyllous (epitepalous).
  • Gynoecium: G̱(3), tricarpellary syncarpous; superior ovary, trilocular with many ovules, axile placentation.
  • Fruit: Capsule, rarely berry. Seed: endospermic.
  • Floral Formula: Br ⊕ ⚥ P(3+3) A3+3 G̱(3)
  • Economic Importance: Ornamentals (Tulip, Gloriosa), Medicine (Aloe), Vegetables (Asparagus), Colchicine (Colchicum autumnale).

Multiple Choice Questions (MCQs)

1. Pneumatophores are modifications of roots found typically in plants growing in:
   a) Sandy soils
   b) Saline soils
   c) Swampy/Mangrove areas
   d) Xerophytic conditions

2. Which of the following is an example of a stem modified into a phylloclade?
   a) Asparagus
   b) Opuntia
   c) Potato
   d) Ginger

3. Vexillary aestivation of corolla is a characteristic feature of the family:
   a) Solanaceae
   b) Liliaceae
   c) Fabaceae
   d) Brassicaceae

4. In a flower with a superior ovary, the floral condition is termed:
   a) Epigynous
   b) Perigynous
   c) Hypogynous
   d) Isogynous

5. The edible part of a coconut ( Cocos nucifera ) fruit is the:
   a) Mesocarp
   b) Endosperm
   c) Pericarp
   d) Epicarp

6. Match the placentation type with its example:
   (i) Marginal (A) Dianthus
   (ii) Axile (B) Pea
   (iii) Parietal (C) Lemon
   (iv) Free central (D) Mustard
   a) (i)-B, (ii)-C, (iii)-D, (iv)-A
   b) (i)-B, (ii)-D, (iii)-A, (iv)-C
   c) (i)-A, (ii)-C, (iii)-D, (iv)-B
   d) (i)-C, (ii)-A, (iii)-B, (iv)-D

7. Identify the correct floral formula for the Liliaceae family:
   a) % ⚥ K(5) C1+2+(2) A(9)+1 G̱1
   b) ⊕ ⚥ K(5) C(5) A5 G̱(2)
   c) Br ⊕ ⚥ P(3+3) A3+3 G̱(3)
   d) ⊕ ⚥ K2+2 C4 A2+4 G̱(2)

8. A fruit that develops from a multicarpellary, syncarpous, inferior ovary with seeds embedded in pulp is likely a:
   a) Drupe
   b) Berry (like Guava)
   c) Legume
   d) Aggregate fruit

9. In monocotyledonous seeds, the plumule is protected by a sheath called:
   a) Coleorhiza
   b) Scutellum
   c) Aleurone layer
   d) Coleoptile

10. Stilt roots, providing mechanical support, are found in:
    a) Banyan tree
    b) Rhizophora
    c) Sugarcane
    d) Sweet Potato

Answer Key for MCQs:

1. c) Swampy/Mangrove areas
2. b) Opuntia
3. c) Fabaceae
4. c) Hypogynous
5. b) Endosperm
6. a) (i)-B, (ii)-C, (iii)-D, (iv)-A
7. c) Br ⊕ ⚥ P(3+3) A3+3 G̱(3)
8. b) Berry (like Guava) - Guava has an inferior ovary.
9. d) Coleoptile
10. c) Sugarcane

Remember to revise these concepts thoroughly, focusing on the definitions, examples, and distinguishing features, especially for the families. Good luck with your preparation!