Class 12 Notes

Class 12 Biology Notes Chapter 1 (Chapter 1) – Lab Manual (English) Book

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Philoid

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Lab Manual (English)
Detailed Notes with MCQs of Chapter 1 from your Biology Lab Manual. This chapter deals with the study of common flowering plants belonging to three important families: Solanaceae, Fabaceae, and Liliaceae. Understanding these families is crucial not just for your practical exams but also forms a basis for many questions in competitive government exams related to Biology or Agriculture. We'll cover their key characteristics, learn how to write floral formulae, draw floral diagrams, and understand their economic significance.

Chapter 1: Study of Flowering Plants (Solanaceae, Fabaceae, Liliaceae)

I. Introduction: Basics of Floral Morphology

Before diving into families, let's revise some terms:

  • Floral Whorls: Calyx (sepals), Corolla (petals), Androecium (stamens), Gynoecium (carpels/pistil).
  • Symmetry:
    • Actinomorphic (⊕): Radial symmetry (can be divided into equal halves by any vertical plane passing through the centre). E.g., Petunia (Solanaceae), Onion (Liliaceae).
    • Zygomorphic (%): Bilateral symmetry (can be divided into equal halves by only one specific vertical plane). E.g., Pea (Fabaceae).
  • Ovary Position:
    • Hypogynous Flower: Ovary superior; other floral parts arise below it. (Indicated by G underlined: G̲). E.g., Solanaceae, Liliaceae.
    • Perigynous Flower: Ovary half-inferior/superior; floral parts arise from the rim of the thalamus cup. (Indicated by G with a dash: G-).
    • Epigynous Flower: Ovary inferior; floral parts arise above the ovary. (Indicated by G overlined: G̅ ).
  • Aestivation: Arrangement of sepals or petals in a floral bud.
    • Valvate: Edges just touch. E.g., Calyx in Solanaceae.
    • Twisted: One margin overlaps the next.
    • Imbricate: Irregular overlapping.
    • Vexillary (Papilionaceous): Largest petal (standard/vexillum) overlaps two lateral petals (wings/alae), which in turn overlap the two smallest anterior petals (keel/carina, often fused). Characteristic of Fabaceae.
  • Placentation: Arrangement of ovules within the ovary.
    • Marginal: Ovules on the ventral suture (ridge) of a monocarpellary or unilocular ovary. E.g., Fabaceae.
    • Axile: Ovules attached to the central axis in a multilocular ovary. E.g., Solanaceae, Liliaceae.
    • Parietal: Ovules on the inner wall of a unilocular ovary.
    • Basal: Single ovule at the base of a unilocular ovary.
    • Free-central: Ovules on the central axis, septa absent.
  • Stamen Conditions:
    • Epipetalous: Stamens attached to petals. E.g., Solanaceae.
    • Epiphyllous/Epitepalous: Stamens attached to perianth lobes (tepals). E.g., Liliaceae.
    • Diadelphous: Stamens united into two bundles. E.g., Fabaceae (9)+1.
    • Monadelphous: Stamens united into one bundle.
    • Polyadelphous: Stamens united into more than two bundles.

II. Family: Solanaceae (The Potato or Nightshade Family)

  1. Systematic Position: Class - Dicotyledonae, Subclass - Gamopetalae, Series - Bicarpellatae, Order - Polemoniales, Family - Solanaceae.
  2. Vegetative Characters:
    • Habit: Mostly herbs, shrubs, rarely small trees.
    • Stem: Herbaceous or woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or smooth (glabrous), often underground stem (tuber in Solanum tuberosum - potato).
    • Leaves: Alternate, simple, rarely pinnately compound, exstipulate; venation reticulate.
  3. Floral Characters:
    • Inflorescence: Solitary, axillary or cymose (as in Solanum).
    • Flower: Bisexual, actinomorphic (⊕).
    • Calyx: 5 sepals, united (gamosepalous), persistent, valvate aestivation (K(5)).
    • Corolla: 5 petals, united (gamopetalous), often bell-shaped or funnel-shaped, valvate or twisted aestivation (C(5)).
    • Androecium: 5 stamens, epipetalous (attached to petals), alternate with petals (A5, attached to C).
    • Gynoecium: Bicarpellary (2 carpels), syncarpous (fused), ovary superior (G̲(2)), bilocular (two chambers), placenta swollen with many ovules, axile placentation. Style simple, stigma bifid or capitate. Ovary obliquely placed.
    • Fruit: Berry (Solanum, Lycopersicon) or capsule (Petunia, Datura).
    • Seed: Many, endospermous.
  4. Floral Formula: ⊕ ⚥ K(5) C(5) A5 G̲(2)
    (Note: The arc above C and A indicates epipetalous condition)
  5. Floral Diagram: (Refer to Lab Manual/Textbook for diagram - shows 5 fused sepals, 5 fused petals, 5 epipetalous stamens, bicarpellary syncarpous superior ovary with axile placentation, mother axis position).
  6. Economic Importance:
    • Food: Potato (Solanum tuberosum), Tomato (Lycopersicon esculentum), Brinjal (Solanum melongena), Chilli (Capsicum annuum).
    • Medicine: Belladonna (Atropa belladonna), Ashwagandha (Withania somnifera), Datura (Datura stramonium).
    • Fumigatory: Tobacco (Nicotiana tabacum).
    • Ornamentals: Petunia, Cestrum (Night queen).

III. Family: Fabaceae (The Pea or Legume Family - Subfamily: Papilionoideae)

  1. Systematic Position: Class - Dicotyledonae, Subclass - Polypetalae, Series - Calyciflorae, Order - Rosales, Family - Leguminosae, Subfamily - Papilionoideae (often treated as Family Fabaceae).
  2. Vegetative Characters:
    • Habit: Trees, shrubs, herbs; root nodules containing nitrogen-fixing bacteria (Rhizobium) are common.
    • Stem: Erect or climber.
    • Leaves: Alternate, pinnately compound or simple; leaf base pulvinate (swollen); stipulate; venation reticulate. Leaflets or entire leaf modified into tendrils in some (e.g., Pea).
  3. Floral Characters:
    • Inflorescence: Racemose.
    • Flower: Bisexual, zygomorphic (%).
    • Calyx: 5 sepals, gamosepalous, valvate or imbricate aestivation (K(5)).
    • Corolla: 5 petals, polypetalous, papilionaceous (butterfly-shaped), consisting of a posterior standard (vexillum), two lateral wings (alae), and two anterior fused ones forming a keel (carina); vexillary aestivation (C 1+2+(2)).
    • Androecium: 10 stamens, diadelphous (9 united into a tube, 1 posterior free) (A (9)+1), anthers dithecous.
    • Gynoecium: Monocarpellary (1 carpel), ovary superior (G̲1), unilocular with many ovules on the ventral suture, marginal placentation. Style single, bent; stigma simple.
    • Fruit: Legume (pod).
    • Seed: One to many, non-endospermic.
  4. Floral Formula: % ⚥ K(5) C 1+2+(2) A (9)+1 G̲1
  5. Floral Diagram: (Refer to Lab Manual/Textbook - shows zygomorphic symmetry, 5 fused sepals, 5 petals in vexillary arrangement, 10 stamens (9 fused + 1 free), monocarpellary superior ovary with marginal placentation).
  6. Economic Importance:
    • Pulses (major source of protein): Gram (Cicer arietinum), Pea (Pisum sativum), Arhar (Cajanus cajan), Moong (Vigna radiata), Soyabean (Glycine max), Lentil (Lens culinaris).
    • Edible Oil: Soyabean, Groundnut (Arachis hypogaea).
    • Dye: Indigo (Indigofera tinctoria).
    • Fibres: Sunn hemp (Crotalaria juncea).
    • Fodder: Sesbania, Trifolium (Clover).
    • Ornamentals: Lupin (Lupinus), Sweet pea (Lathyrus odoratus).
    • Medicine: Muliathi (Glycyrrhiza glabra).

IV. Family: Liliaceae (The Lily Family)

  1. Systematic Position: Class - Monocotyledonae, Series - Coronarieae, Family - Liliaceae.
  2. Vegetative Characters:
    • Habit: Perennial herbs with underground bulbs, corms, or rhizomes.
    • Stem: Mostly underground. Aerial scape (flower stalk) present.
    • Leaves: Mostly basal, alternate, linear, exstipulate; venation parallel.
  3. Floral Characters:
    • Inflorescence: Solitary / cymose; often umbellate clusters (e.g., Onion).
    • Flower: Bisexual, actinomorphic (⊕).
    • Perianth: Tepals 6 (3+3), often united into a tube (gamophyllous/gamotepalous); valvate or imbricate aestivation (P (3+3) or P 3+3). Tepals indistinguishable from sepals and petals.
    • Androecium: 6 stamens, in two whorls (3+3), epiphyllous/epitepalous (attached to tepals) (A 3+3, attached to P).
    • Gynoecium: Tricarpellary (3 carpels), syncarpous (fused), ovary superior (G̲(3)), trilocular (three chambers) with many ovules, axile placentation. Style simple; stigma trilobed or capitate.
    • Fruit: Capsule, rarely berry.
    • Seed: Endospermous.
  4. Floral Formula: ⊕ ⚥ P (3+3) A 3+3 G̲(3)
    (Note: The arc above P and A indicates epiphyllous/epitepalous condition)
  5. Floral Diagram: (Refer to Lab Manual/Textbook - shows actinomorphic symmetry, 6 tepals in two whorls, 6 epiphyllous stamens in two whorls, tricarpellary syncarpous superior ovary with axile placentation).
  6. Economic Importance:
    • Ornamentals: Tulip (Tulipa), Lily (Lilium), Gloriosa.
    • Vegetables: Onion (Allium cepa), Garlic (Allium sativum), Asparagus.
    • Medicine: Aloe vera, Colchicum autumnale (source of colchicine), Smilax.

V. Dissection and Observation

  • Flower Dissection: Carefully remove whorls (calyx, corolla, androecium, gynoecium) using forceps and needle, arrange them sequentially.
  • Anther: Observe the number of lobes (usually two - dithecous). A transverse section shows pollen sacs (microsporangia).
  • Ovary: Cut a transverse section (T.S.) to observe the number of locules (chambers) and the type of placentation (arrangement of ovules).

VI. Key Symbols Recap

  • ⊕ : Actinomorphic
  • % : Zygomorphic
  • ⚥ : Bisexual
  • K : Calyx (K(n) = fused sepals, Kn = free sepals)
  • C : Corolla (C(n) = fused petals, Cn = free petals)
  • P : Perianth (P(n) = fused tepals, Pn = free tepals)
  • A : Androecium (An = free stamens, A(n) = fused stamens, A(n)+(m) = diadelphous)
  • G : Gynoecium (G(n) = syncarpous, Gn = apocarpous, G̲ = superior ovary, G̅ = inferior ovary)
  • ⌒ (arc above letters): Adhesion (e.g., C͡A indicates epipetalous stamens)

Multiple Choice Questions (MCQs)

Here are 10 MCQs based on the chapter content for your practice:

  1. Which of the following floral formulae represents the Family Liliaceae?
    a) % ⚥ K(5) C 1+2+(2) A (9)+1 G̲1
    b) ⊕ ⚥ K(5) C(5) A5 G̲(2)
    c) ⊕ ⚥ P (3+3) A 3+3 G̲(3)
    d) ⊕ ⚥ K4 C4 A 2+4 G̲(2)

  2. Vexillary aestivation and diadelphous stamens are characteristic features of which family?
    a) Solanaceae
    b) Fabaceae
    c) Liliaceae
    d) Malvaceae

  3. Axile placentation is found in the ovaries of:
    a) Fabaceae and Liliaceae
    b) Solanaceae and Fabaceae
    c) Solanaceae and Liliaceae
    d) Only Fabaceae

  4. Epipetalous stamens (stamens attached to petals) are commonly found in:
    a) Allium cepa (Onion)
    b) Solanum nigrum (Black Nightshade)
    c) Pisum sativum (Pea)
    d) Asparagus

  5. The gynoecium in the family Solanaceae is typically:
    a) Monocarpellary, superior ovary
    b) Bicarpellary, syncarpous, superior ovary
    c) Tricarpellary, syncarpous, inferior ovary
    d) Bicarpellary, apocarpous, superior ovary

  6. A flower that can be divided into two equal halves by only one vertical plane is called:
    a) Actinomorphic
    b) Zygomorphic
    c) Asymmetric
    d) Isomerous

  7. In the floral formula ⊕ ⚥ K(5) C(5) A5 G̲(2), the symbol G̲(2) indicates:
    a) Gynoecium with 2 free carpels, inferior ovary
    b) Gynoecium with 2 fused carpels, superior ovary
    c) Gynoecium with 2 fused carpels, inferior ovary
    d) Gynoecium with 2 free carpels, superior ovary

  8. Pulses like Gram, Arhar, and Moong belong to which economically important plant family?
    a) Solanaceae
    b) Liliaceae
    c) Fabaceae
    d) Poaceae

  9. Allium cepa (Onion) and Aloe vera are examples belonging to the family:
    a) Fabaceae
    b) Solanaceae
    c) Liliaceae
    d) Asteraceae

  10. A key vegetative feature distinguishing Liliaceae from Solanaceae and Fabaceae is:
    a) Presence of root nodules
    b) Reticulate venation in leaves
    c) Parallel venation in leaves
    d) Presence of stipules

Answer Key for MCQs:

  1. c
  2. b
  3. c
  4. b
  5. b
  6. b
  7. b
  8. c
  9. c
  10. c

Study these notes thoroughly. Pay close attention to the distinguishing features, floral formulae, and economic importance of each family. Practice drawing the floral diagrams as well. This will solidify your understanding for any exam. Good luck!

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