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Class 11 Biology Notes Chapter 5 (Chapter 5) – Lab Manual (English) Book

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Philoid

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Lab Manual (English)
Detailed Notes with MCQs of Chapter 5 from your Biology Lab Manual. This chapter deals with the practical aspects of the Morphology of Flowering Plants, which is a very important topic for your exams. We'll cover the key observations and concepts you need to know.

Chapter 5: Study of Morphology of Flowering Plants (Practical Aspects)

This chapter typically involves the study of various plant parts, their modifications, and arrangements. The focus is on observation and identification based on morphological features.

1. Root Modifications:

  • Purpose: Roots are modified for functions other than absorption and anchorage, such as storage, support, and respiration.
  • Types & Examples:
    • For Storage:
      • Tap Root Modifications:
        • Fusiform: Spindle-shaped, swollen in the middle, tapering at both ends (e.g., Radish - Raphanus sativus).
        • Napiform: Spherical at the base, abruptly tapering towards the apex (e.g., Turnip - Brassica rapa, Beetroot - Beta vulgaris).
        • Conical: Cone-shaped, broad at the base, gradually tapering towards the apex (e.g., Carrot - Daucus carota).
      • Adventitious Root Modifications:
        • Tuberous: Swollen, irregular shape, arising from nodes of the stem (e.g., Sweet Potato - Ipomoea batatas).
        • Fasciculated: Cluster of tuberous roots arising from the base of the stem (e.g., Dahlia, Asparagus).
        • Nodulose: Swellings occur only near the tips (e.g., Mango ginger - Curcuma amada).
        • Moniliform/Beaded: Swollen at regular intervals like beads (e.g., Indian spinach - Basella, Bitter gourd - Momordica).
    • For Support:
      • Prop Roots: Arise from horizontal branches, grow downwards vertically for support (e.g., Banyan - Ficus benghalensis).
      • Stilt Roots: Arise from lower nodes of the stem, grow obliquely downwards for support (e.g., Maize - Zea mays, Sugarcane - Saccharum officinarum, Screwpine - Pandanus).
      • Climbing Roots: Arise from nodes, help the plant climb (e.g., Money Plant - Pothos, Betel - Piper betle).
    • For Respiration (Pneumatophores): Negatively geotropic roots (grow upwards) found in marshy/saline areas (mangroves), have pores (lenticels/pneumathodes) for gaseous exchange (e.g., Rhizophora, Avicennia, Sonneratia).
    • Haustorial/Parasitic Roots: Penetrate host tissues to absorb nutrients (e.g., Cuscuta - dodder).
    • Epiphytic/Hygroscopic Roots: Found in epiphytes (plants growing on other plants for support only), have velamen tissue to absorb atmospheric moisture (e.g., Orchids like Vanda).

2. Stem Modifications:

  • Purpose: Stems are modified for storage, perennation (survival during unfavourable conditions), vegetative propagation, protection, support, and photosynthesis.
  • Types & Examples:
    • Underground Stem Modifications (for Storage & Perennation):
      • Rhizome: Thick, fleshy, horizontal/prostrate stem with nodes, internodes, scale leaves, and buds (e.g., Ginger - Zingiber officinale, Turmeric - Curcuma longa, Ferns).
      • Tuber: Swollen underground stem tip, possesses 'eyes' (nodes) with buds (e.g., Potato - Solanum tuberosum). Distinguish from tuberous roots (like sweet potato) by presence of nodes/eyes.
      • Bulb: Condensed, disc-like underground stem surrounded by fleshy scale leaves (storage) or dry, papery leaves (tunic). (e.g., Onion - Allium cepa, Garlic - Allium sativum).
      • Corm: Condensed, fleshy, vertically growing underground stem with nodes, internodes, buds, and scale leaves (e.g., Colocasia - Arbi, Crocus - Saffron, Amorphophallus - Zaminkand).
    • Sub-aerial Stem Modifications (for Vegetative Propagation):
      • Runner: Slender, prostrate branch with long internodes, rooting at nodes (e.g., Grasses - Cynodon dactylon, Strawberry - Fragaria, Oxalis).
      • Stolon: Arches down from the base of the stem to touch the ground and root (e.g., Jasmine - Jasminum, Mint - Mentha).
      • Offset: Like a runner but shorter, thicker, found in aquatic plants (e.g., Water hyacinth - Eichhornia, Water lettuce - Pistia).
      • Sucker: Arises from the basal underground part of the main stem, grows obliquely upwards (e.g., Chrysanthemum, Banana, Pineapple).
    • Aerial Stem Modifications:
      • Stem Tendrils: Thread-like, coiled structures for climbing; modification of axillary bud (e.g., Cucumber, Pumpkin, Watermelon, Grapevine - Vitis) or apical bud (e.g., Passiflora).
      • Thorns: Hard, pointed structures for protection; modification of axillary bud (e.g., Citrus, Bougainvillea, Duranta). Note: Spines are modified leaves/stipules (e.g., Cactus), Prickles are superficial outgrowths (e.g., Rose).
      • Phylloclade: Flattened or cylindrical green stem performing photosynthesis; leaves reduced to spines or scales; unlimited growth (e.g., Opuntia - flattened, Euphorbia - cylindrical). Has nodes and internodes.
      • Cladode: Green stem segments (usually one internode long) performing photosynthesis; limited growth (e.g., Asparagus, Ruscus).

3. Leaf Modifications:

  • Purpose: Leaves modified for support, protection, storage, trapping insects, etc.
  • Types & Examples:
    • Leaf Tendrils: For climbing. Entire leaf (e.g., Wild Pea - Lathyrus aphaca), Leaflet (e.g., Sweet Pea - Pisum sativum), Leaf tip (e.g., Gloriosa), Stipules (e.g., Smilax).
    • Spines: For protection, reducing transpiration (e.g., Cacti like Opuntia, Berberis).
    • Phyllode: Petiole becomes flattened, green, and leaf-like to perform photosynthesis; lamina is reduced or absent (e.g., Australian Acacia - Acacia auriculiformis).
    • Storage Leaves: Fleshy leaves store food (e.g., Onion, Garlic) or water (e.g., Aloe, Agave).
    • Pitcher Plant: Lamina modified into a pitcher to trap insects (e.g., Nepenthes, Sarracenia).
    • Bladderwort: Leaf segments modified into bladders to trap small aquatic organisms (e.g., Utricularia - aquatic).
    • Venus Flytrap: Lamina modified into two lobes with sensitive trigger hairs to trap insects (e.g., Dionaea).

4. Inflorescence:

  • Definition: The arrangement of flowers on the floral axis (peduncle).
  • Main Types:
    • Racemose: Main axis continues to grow (indeterminate); flowers arranged acropetally (older flowers at the base, younger at the apex).
      • Raceme: Pedicellate flowers on an elongated axis (e.g., Radish, Mustard - Brassica).
      • Spike: Sessile flowers on an elongated axis (e.g., Achyranthes, Grasses).
      • Spikelet: Unit of grass inflorescence, small spike with bracts (glumes, lemma, palea).
      • Catkin/Amentum: Pendulous spike with unisexual flowers (e.g., Mulberry - Morus, Oak - Quercus).
      • Spadix: Spike with fleshy axis, covered by a large colorful bract (spathe) (e.g., Maize, Colocasia, Banana, Palms).
      • Corymb: Main axis short; lower flowers have longer pedicels than upper ones, bringing all flowers to roughly the same level (e.g., Candytuft - Iberis).
      • Umbel: Flowers arise from a common point (tip of peduncle), usually with an involucre (whorl of bracts) at the base (e.g., Coriander - Coriandrum, Fennel - Foeniculum, Carrot). Compound Umbel is characteristic of Apiaceae/Umbelliferae family.
      • Capitulum/Head: Sessile flowers (florets) crowded on a flattened receptacle, surrounded by involucre bracts. Characteristic of Asteraceae/Compositae family (e.g., Sunflower - Helianthus, Marigold - Tagetes). Ray florets (peripheral, often zygomorphic, ligulate) and Disc florets (central, actinomorphic, tubular).
    • Cymose: Main axis terminates in a flower (limited/determinate growth); subsequent flowers arise from lateral buds below, arranged basipetally (older flower at the apex, younger at the base).
      • Solitary Cyme: Single terminal flower (e.g., Hibiscus, Poppy).
      • Monochasial Cyme (Uniparous): Main axis ends in a flower; one lateral branch develops below it. Can be Helicoid (branches on same side, e.g., Drosera, Begonia) or Scorpioid (branches on alternate sides, e.g., Heliotropium, Ranunculus).
      • Dichasial Cyme (Biparous): Main axis ends in a flower; two lateral branches develop below it (e.g., Jasmine, Dianthus, Bougainvillea).
      • Polychasial Cyme (Multiparous): Main axis ends in a flower; more than two lateral branches develop below it (e.g., Calotropis).
    • Special Types:
      • Cyathium: Cup-shaped involucre enclosing a single central female flower and numerous peripheral male flowers (each represented by a single stamen). Found in Euphorbia.
      • Verticillaster: Clusters of sessile/subsessile flowers arranged in cymose manner at nodes, appearing as a whorl around the stem. Characteristic of Lamiaceae/Labiatae family (e.g., Tulsi - Ocimum, Mint - Mentha, Salvia).
      • Hypanthodium: Receptacle forms a closed, pear-shaped structure with an apical opening (ostiole); unisexual flowers borne on the inner wall (e.g., Fig - Ficus).

5. Flower Structure (Example: Hibiscus/Petunia):

  • Pedicel: Stalk of the flower.
  • Thalamus/Receptacle: Swollen end of pedicel where floral whorls are attached.
  • Floral Whorls:
    • Calyx: Outermost whorl, units called sepals. Usually green, protective. Gamosepalous (fused), Polysepalous (free).
    • Corolla: Next whorl, units called petals. Usually brightly colored, attract pollinators. Gamopetalous (fused), Polypetalous (free).
    • Androecium: Male reproductive whorl, units called stamens. Each stamen has a filament (stalk) and an anther (contains pollen sacs/microsporangia). Polyandrous (free), Monadelphous (filaments fused into one bundle, e.g., Hibiscus), Diadelphous (two bundles, e.g., Pea), Polyadelphous (many bundles, e.g., Citrus). Epipetalous (stamens attached to petals, e.g., Brinjal, Petunia).
    • Gynoecium/Pistil: Innermost whorl, female reproductive part, units called carpels. Each carpel (or fused carpels) has stigma (receptive surface for pollen), style (stalk connecting stigma to ovary), and ovary (basal swollen part containing ovules). Apocarpous (carpels free, e.g., Rose, Lotus), Syncarpous (carpels fused, e.g., Mustard, Tomato, Hibiscus).
  • Symmetry:
    • Actinomorphic (Radial): Can be divided into two equal halves by any vertical plane passing through the center (e.g., Mustard, Datura, Chilli, Petunia). Symbol: ⊕
    • Zygomorphic (Bilateral): Can be divided into two equal halves by only one specific vertical plane (e.g., Pea, Bean, Gulmohur, Cassia, Salvia). Symbol: %
  • Insertion of Floral Whorls on Thalamus (Ovary Position):
    • Hypogynous: Gynoecium occupies the highest position; other parts are below it. Ovary is superior (e.g., Mustard, China rose/Hibiscus, Brinjal, Petunia).
    • Perigynous: Gynoecium in the center; other parts on the rim of the thalamus almost at the same level. Ovary is half-inferior (e.g., Plum, Rose, Peach).
    • Epigynous: Thalamus grows upward enclosing the ovary completely and fuses with it; other parts arise above the ovary. Ovary is inferior (e.g., Guava, Cucumber, Ray florets of Sunflower).

6. Fruit Types:

  • Fruit: Mature or ripened ovary, developed after fertilization.
  • Pericarp: Fruit wall, developed from the ovary wall. Differentiated into outer epicarp, middle mesocarp, and inner endocarp.
  • Types:
    • Simple Fruits: Develop from a single carpel or syncarpous ovary of a single flower.
      • Fleshy Fruits: Pericarp is fleshy.
        • Drupe: Stony endocarp (e.g., Mango, Coconut, Peach, Plum, Cherry). Edible part in Mango is mesocarp; in Coconut, it's the endosperm.
        • Berry: Fleshy pericarp, endocarp soft, seeds embedded in pulp (e.g., Tomato, Guava, Grapes, Brinjal, Banana).
        • Pepo: Berry with a hard rind, develops from inferior ovary (Cucurbitaceae family) (e.g., Cucumber, Watermelon, Pumpkin).
        • Hesperidium: Berry with leathery rind containing oil glands, develops from superior, multicarpellary, syncarpous ovary (Citrus family) (e.g., Orange, Lemon).
        • Pome: False fruit (thalamus also contributes to fruit formation), develops from inferior ovary (e.g., Apple, Pear). Edible part is fleshy thalamus.
      • Dry Fruits: Pericarp is dry.
        • Dehiscent: Pericarp splits open at maturity.
          • Legume/Pod: Dehisces along both dorsal and ventral sutures (e.g., Pea, Bean - Fabaceae family).
          • Follicle: Dehisces along one suture only (e.g., Calotropis, Larkspur).
          • Siliqua: Dehisces along two sutures from base upwards, seeds on a false septum (replum) (e.g., Mustard - Brassicaceae family). Silicula is a short, broad version.
          • Capsule: Dehisces in various ways (pores, valves, etc.) (e.g., Cotton, Datura, Lady's finger/Okra).
        • Indehiscent: Pericarp does not split open.
          • Achene: Small, single-seeded, pericarp free from seed coat (e.g., Mirabilis, Clematis).
          • Caryopsis: Small, single-seeded, pericarp fused with seed coat (Grain) (e.g., Maize, Wheat, Rice - Poaceae family).
          • Cypsela: Single-seeded, develops from inferior, bicarpellary ovary, often with persistent pappus (modified calyx) (e.g., Sunflower, Marigold - Asteraceae family).
          • Nut: Single-seeded, hard, stony pericarp (e.g., Cashew nut - true nut part is the kidney-shaped structure, Oak - Acorn, Litchi - edible part is fleshy aril, not pericarp).
          • Samara: Winged achene (e.g., Maple, Hiptage, Ash - Fraxinus).
    • Aggregate Fruits: Develop from a multicarpellary, apocarpous ovary of a single flower. Each carpel develops into a fruitlet. Collection of fruitlets is called an etaerio (e.g., Etaerio of achenes in Strawberry - edible part is fleshy thalamus, Etaerio of drupes in Raspberry, Etaerio of follicles in Calotropis).
    • Multiple/Composite Fruits: Develop from a complete inflorescence (e.g., Sorosis from spadix/spike - Jackfruit, Pineapple, Mulberry; Syconus from hypanthodium - Fig).
    • Parthenocarpic Fruits: Develop without fertilization (seedless) (e.g., Banana, some Grapes varieties).

7. Seed Structure:

  • Seed: Mature ovule containing an embryo and stored food, covered by a protective seed coat.
  • Seed Coat: Develops from integuments of the ovule. Outer layer is testa, inner is tegmen.
  • Embryo: Consists of an embryonal axis and one or two cotyledons.
    • Embryonal Axis: Has plumule (develops into shoot) and radicle (develops into root). The point of attachment of cotyledons is the embryonal node. Portion above it is epicotyl, below it is hypocotyl.
  • Endosperm: Food-storing tissue, may or may not be present in mature seed.
    • Albuminous/Endospermic Seeds: Retain endosperm at maturity (e.g., Castor, Maize, Wheat, Barley, Coconut).
    • Exalbuminous/Non-endospermic Seeds: Endosperm consumed during embryo development; food stored in cotyledons (e.g., Pea, Bean, Gram, Groundnut).
  • Dicot Seed (e.g., Bean, Gram, Pea):
    • Seed coat (testa, tegmen).
    • Hilum (scar where seed was attached to fruit).
    • Micropyle (small pore near hilum).
    • Embryo with embryonal axis and two large, fleshy cotyledons (store food).
    • No endosperm (exalbuminous).
  • Monocot Seed (e.g., Maize, Rice, Wheat):
    • Seed coat fused with pericarp (caryopsis).
    • Endosperm (large, stores food, usually starchy). Separated from embryo by proteinaceous aleurone layer.
    • Embryo (small, situated in a groove at one end of endosperm).
    • Single large, shield-shaped cotyledon called scutellum.
    • Embryonal axis with plumule covered by coleoptile (protective sheath) and radicle covered by coleorhiza (protective sheath).

Practice MCQs:

  1. Pneumatophores are characteristic modifications found in plants growing in:
    a) Sandy deserts
    b) Saline marshy areas
    c) Temperate forests
    d) Freshwater lakes

  2. Which of the following is an example of a stem tuber?
    a) Carrot
    b) Sweet Potato
    c) Potato
    d) Radish

  3. In Bougainvillea, the thorns are modifications of:
    a) Stipules
    b) Adventitious roots
    c) Axillary buds
    d) Leaves

  4. A flower which can be divided into two equal radial halves in any radial plane passing through the centre is said to be:
    a) Zygomorphic
    b) Asymmetric
    c) Actinomorphic
    d) Epigynous

  5. An inflorescence where the main axis terminates in a flower, and flowers are borne in a basipetal order is:
    a) Racemose
    b) Cymose
    c) Capitulum
    d) Umbel

  6. The ovary is said to be half-inferior in which of the following conditions?
    a) Hypogynous
    b) Perigynous
    c) Epigynous
    d) Syngenesious

  7. Which type of fruit develops from a single flower with a syncarpous, inferior ovary and has a hard rind?
    a) Drupe
    b) Berry
    c) Pepo
    d) Hesperidium

  8. The edible part of a coconut (Cocos nucifera) is primarily the:
    a) Mesocarp
    b) Endocarp
    c) Fleshy thalamus
    d) Endosperm

  9. In maize grain (a monocot seed), the proteinaceous layer separating the embryo from the endosperm is called:
    a) Scutellum
    b) Coleoptile
    c) Aleurone layer
    d) Coleorhiza

  10. Phylloclades are:
    a) Modified petioles performing photosynthesis
    b) Flattened/cylindrical green stems performing photosynthesis
    c) Modified leaves for storing water
    d) Underground stems for perennation

Answer Key:

  1. b) Saline marshy areas
  2. c) Potato
  3. c) Axillary buds
  4. c) Actinomorphic
  5. b) Cymose
  6. b) Perigynous
  7. c) Pepo
  8. d) Endosperm
  9. c) Aleurone layer
  10. b) Flattened/cylindrical green stems performing photosynthesis

Remember to correlate these practical observations with the theory chapter on Morphology of Flowering Plants. Pay close attention to the examples provided, as they are frequently asked in competitive exams. Good luck with your preparation!

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