Class 11 Biology Notes Chapter 2 (Chapter 2) – Lab Manual (English) Book

Detailed Notes with MCQs of the practical aspects covered in the experiments typically grouped early in your Class 11 Biology Lab Manual, often considered under the umbrella of 'Chapter 2' for organizational purposes. These experiments are crucial not just for your practical exams but also form a basis for many questions in competitive government exams. We'll cover Plant Families and Plant Anatomy in detail.

Chapter 2: Study of Plant Families and Anatomy

This section primarily deals with understanding the morphology of common flowering plants and the internal structure (anatomy) of roots and stems.

Part 1: Study of Flowering Plants (Morphology & Floral Characteristics)

Objective: To study and describe locally available common flowering plants belonging to specific families (e.g., Solanaceae, Fabaceae, Liliaceae) including dissection and display of floral parts, floral formula, and floral diagram.

Key Concepts:

1. Plant Description: Requires systematic description starting from habit (herb, shrub, tree), root system (tap/fibrous), stem (herbaceous/woody, modifications), leaf (type, venation, phyllotaxy).
2. Inflorescence: Arrangement of flowers on the floral axis (e.g., solitary, cymose, racemose).
3. Flower: Reproductive unit. Described based on:
   • Symmetry: Actinomorphic (radial symmetry, e.g., Mustard, Datura, Chilli) or Zygomorphic (bilateral symmetry, e.g., Pea, Bean, Gulmohar).
   • Sexuality: Unisexual or Bisexual.
   • Position of Ovary: Hypogynous (superior ovary, e.g., Mustard, Brinjal), Perigynous (half-inferior ovary, e.g., Rose, Plum), Epigynous (inferior ovary, e.g., Guava, Cucumber).
   • Whorls: Calyx (sepals), Corolla (petals), Androecium (stamens), Gynoecium (carpels).
4. Floral Formula: A symbolic representation of floral characters. Symbols used:
   • Br (Bracteate), Ebr (Ebracteate)
   • ⊕ (Actinomorphic), % (Zygomorphic)
   • ⚥ (Bisexual), ♂ (Male), ♀ (Female)
   • K (Calyx), C (Corolla), P (Perianth - when calyx & corolla are indistinct)
   • A (Androecium), G (Gynoecium)
   • Number of parts in a whorl written as subscript (e.g., K₅).
   • Fusion indicated by brackets ( ) (e.g., K₍₅₎).
   • Adhesion indicated by a line above symbols (e.g., C͡A - epipetalous).
   • Gynoecium position: G̱ (Superior ovary), G̅ (Inferior ovary), G- (Half-inferior).
5. Floral Diagram: Ground plan of a flower showing the number, arrangement, cohesion, and adhesion of floral parts in relation to the mother axis.

Family: Solanaceae (Potato family)

• Habit: Mostly herbs, shrubs, rarely small trees.
• Stem: Herbaceous/woody, aerial, erect, cylindrical, branched, solid/hollow, hairy/glabrous, underground stem in potato (Solanum tuberosum).
• Leaves: Alternate, simple, rarely pinnately compound, exstipulate; reticulate venation.
• Inflorescence: Solitary, axillary or cymose as in Solanum.
• Flower: Bisexual, actinomorphic.
• Calyx: Sepals 5, united (gamosepalous), persistent, valvate aestivation.
• Corolla: Petals 5, united (gamopetalous), valvate aestivation.
• Androecium: Stamens 5, epipetalous (attached to petals).
• Gynoecium: Bicarpellary, syncarpous (united carpels); ovary superior, bilocular, placenta swollen with many ovules, axile placentation. Style simple, stigma bifid.
• Fruit: Berry or capsule.
• Floral Formula: ⊕ ⚥ K₍₅₎ C₍₅₎ A₅ G̱₍₂₎
• Economic Importance: Food (potato, tomato, brinjal, chilli), Spice (chilli), Medicine (belladonna, ashwagandha), Fumigatory (tobacco), Ornamentals (petunia).

Family: Fabaceae (Pea or Legume family) - Subfamily: Papilionoideae

• Habit: Trees, shrubs, herbs; root with root nodules (nitrogen fixation).
• Stem: Erect or climber.
• Leaves: Alternate, pinnately compound or simple; leaf base pulvinate; stipulate; reticulate venation.
• Inflorescence: Racemose.
• Flower: Bisexual, zygomorphic.
• Calyx: Sepals 5, gamosepalous; imbricate/valvate aestivation.
• Corolla: Petals 5, polypetalous, papilionaceous (butterfly-shaped), consisting of a posterior standard (vexillum), two lateral wings (alae), two anterior ones forming a keel (carina, enclosing stamens and pistil); vexillary aestivation.
• Androecium: Stamens 10, diadelphous (9 united + 1 free). Anthers dithecous.
• Gynoecium: Monocarpellary, ovary superior, unilocular with many ovules on marginal placentation. Style single.
• Fruit: Legume.
• Floral Formula: % ⚥ K₍₅₎ C₁₊₂₊₍₂₎ A₍₉₎₊₁ G̱₁
• Economic Importance: Pulses (gram, arhar, moong, soybean), Edible oil (soybean, groundnut), Dye (Indigofera), Fibres (sunn hemp), Fodder (Sesbania, Trifolium), Ornamentals (lupin, sweet pea), Medicine (muliathi).

Family: Liliaceae (Lily family)

• Habit: Perennial herbs with underground bulbs/corms/rhizomes.
• Stem: Aerial or underground.
• Leaves: Mostly basal, alternate, linear, exstipulate; parallel venation.
• Inflorescence: Solitary / cymose; often umbellate clusters.
• Flower: Bisexual, actinomorphic.
• Perianth: Tepals 6 (3+3), often united into a tube (gamotepalous); valvate aestivation. (Perianth = Calyx + Corolla indistinct).
• Androecium: Stamens 6 (3+3), epitepalous (attached to perianth).
• Gynoecium: Tricarpellary, syncarpous; ovary superior, trilocular with many ovules; axile placentation. Style single, stigma trifid.
• Fruit: Capsule, rarely berry.
• Floral Formula: Br ⊕ ⚥ P₍₃₊₃₎ A₃₊₃ G̱₍₃₎
• Economic Importance: Ornamentals (tulip, Gloriosa), Medicine (Aloe), Vegetables (Asparagus), Colchicine source (Colchicum autumnale).

Part 2: Study of Plant Anatomy (Internal Structure)

Objective: To prepare and study transverse sections (T.S.) of dicot and monocot roots and stems (primary structure).

Key Concepts:

• Tissue Systems: Epidermal, Ground, Vascular.
• Epidermal Tissue System: Outermost layer (epidermis), may have cuticle, stomata, epidermal appendages (trichomes, root hairs).
• Ground Tissue System: All tissues except epidermis and vascular bundles. Includes cortex, endodermis, pericycle, pith, medullary rays.
• Vascular Tissue System: Xylem and Phloem, arranged in vascular bundles.

1. Dicot Root (e.g., Sunflower, Gram)

• Epidermis (Epiblema/Rhizodermis): Outermost, single layer, thin-walled cells, no cuticle/stomata, unicellular root hairs present.
• Cortex: Multilayered parenchyma, stores food. Innermost layer is Endodermis.
• Endodermis: Barrel-shaped cells, Casparian strips (suberin deposition) on radial and tangential walls, controls water passage. Passage cells (thin-walled) opposite protoxylem.
• Stele: All tissues inside endodermis.
  • Pericycle: Outermost layer of stele, parenchyma, origin of lateral roots and vascular cambium.
  • Vascular Bundles: Radial (Xylem and Phloem on different radii). Xylem is exarch (protoxylem towards periphery, metaxylem towards center). Number of xylem bundles usually 2-6 (diarch to hexarch). Phloem alternates with xylem.
  • Pith: Small or inconspicuous, parenchymatous.
  • Conjuntive Tissue: Parenchyma between xylem and phloem.

2. Monocot Root (e.g., Maize, Grass)

• Epidermis, Cortex, Endodermis, Pericycle: Similar to dicot root (Casparian strips prominent).
• Vascular Bundles: Radial, Xylem exarch. Number of xylem bundles usually more than 6 (polyarch).
• Pith: Large, well-developed, parenchymatous.
• Secondary Growth: Absent.

Comparison: Dicot Root vs Monocot Root

3. Dicot Stem (e.g., Sunflower)

• Epidermis: Outermost, single layer, cuticle present, multicellular stem hairs (trichomes), few stomata.
• Cortex: Differentiated into:
  • Hypodermis: Collenchymatous (provides mechanical support).
  • General Cortex: Parenchymatous, may contain chloroplasts.
  • Endodermis: Innermost layer, rich in starch grains (Starch Sheath), Casparian strips usually absent.
• Stele:
  • Pericycle: Multilayered, sclerenchymatous (above vascular bundle - bundle cap) and parenchymatous.
  • Vascular Bundles: Conjoint (Xylem & Phloem together), Collateral (Xylem towards center, Phloem towards periphery), Open (Cambium present between Xylem & Phloem). Arranged in a ring. Xylem is endarch (protoxylem towards center, metaxylem towards periphery).
  • Pith: Large, central, parenchymatous.
  • Medullary Rays: Parenchymatous cells between vascular bundles, for radial conduction.

4. Monocot Stem (e.g., Maize, Grass)

• Epidermis: Outermost, single layer, cuticle present, stomata present.
• Hypodermis: Sclerenchymatous (provides mechanical support).
• Ground Tissue: Undifferentiated mass of parenchyma, vascular bundles are scattered within it. No distinct Cortex, Endodermis, Pericycle, Pith, Medullary rays.
• Vascular Bundles: Conjoint, Collateral, Closed (Cambium absent). Scattered arrangement. Each bundle surrounded by a sclerenchymatous bundle sheath. Size larger towards the center, smaller towards periphery. Xylem endarch (often Y-shaped arrangement). Phloem present.
• Secondary Growth: Absent.

Comparison: Dicot Stem vs Monocot Stem

Part 3: Physiological Experiments (Brief Overview)

• Osmosis (Potato Osmometer): Demonstrates movement of water from a region of higher water potential (pure water/dilute solution) to lower water potential (concentrated sugar solution) across a semipermeable membrane (potato cells). Observation: Rise in sugar solution level in the osmometer cavity.
• Plasmolysis (Rhoeo leaf peel): Demonstrates shrinkage of protoplast away from the cell wall when a plant cell is placed in a hypertonic solution (e.g., concentrated salt/sugar solution) due to exosmosis. Observation: Purple cell sap area shrinks. Deplasmolysis occurs if placed back in hypotonic solution/water.
• Stomata Distribution: Study of epidermal peels (upper and lower) shows stomata are usually more numerous on the lower epidermis (dicots) or equally distributed (monocots, isobilateral leaves). Stomata consist of guard cells enclosing a stomatal pore.
• Transpiration Rate Comparison: Using cobalt chloride paper (blue when dry, pink when moist). Paper strips attached to upper and lower surfaces. Faster change to pink indicates a higher rate of transpiration. Usually faster on the lower surface in dicots.
• Biochemical Tests:
  • Sugar (Reducing): Benedict's test. Reagent: Benedict's solution. Positive: Green/Yellow/Orange/Red precipitate on heating.
  • Starch: Iodine test. Reagent: Iodine solution. Positive: Blue-black colour.
  • Protein: Biuret test. Reagent: NaOH + CuSO₄ solution. Positive: Violet/Purple colour.
  • Fats: Sudan III/IV test or Paper spot test. Reagent: Sudan III/IV. Positive: Orange/Red colouration. Paper spot: Translucent spot on paper.
  • Urea (in urine): Urease test (enzyme urease breaks urea into ammonia, detected by smell or indicator) or specific chemical tests.
  • Bile Salts (in urine): Hay's test. Sprinkle sulphur powder on urine surface. Positive: Sulphur sinks (bile salts reduce surface tension).
• Imbibition (Seeds/Raisins): Adsorption of water by hydrophilic colloids in dry seeds/raisins, causing them to swell. It's a type of diffusion where water moves down a water potential gradient. Observation: Increase in volume/weight.

Multiple Choice Questions (MCQs)

1. Which floral formula correctly represents a flower from 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) ⊕ ⚥ K₄ C₄ A₂₊₄ G̱₍₂₎

2. In a dicot stem, the vascular bundles are arranged:
   a) Scattered throughout the ground tissue
   b) In a distinct ring
   c) Radially
   d) Concentrically

3. The presence of Casparian strips is a characteristic feature of which tissue in roots?
   a) Epidermis
   b) Pericycle
   c) Cortex
   d) Endodermis

4. Papilionaceous corolla and diadelphous stamens are characteristic features of which family?
   a) Solanaceae
   b) Liliaceae
   c) Fabaceae
   d) Brassicaceae

5. Which of the following correctly describes the vascular bundles in a monocot stem?
   a) Conjoint, collateral, open, ring arrangement
   b) Conjoint, collateral, closed, scattered
   c) Radial, exarch, polyarch
   d) Conjoint, bicollateral, open, scattered

6. The potato osmometer experiment demonstrates the phenomenon of:
   a) Imbibition
   b) Plasmolysis
   c) Active transport
   d) Osmosis

7. A student observes a T.S. of a plant part showing polyarch, radial vascular bundles and a large, well-developed pith. This section likely belongs to:
   a) Dicot stem
   b) Monocot stem
   c) Dicot root
   d) Monocot root

8. Epipetalous stamens and a superior, bicarpellary, syncarpous ovary with a swollen placenta are found in:
   a) Pea (Pisum sativum)

   • b) Onion (Allium cepa)
     c) Brinjal (Solanum melongena)
     d) Maize (Zea mays)

9. When a Rhoeo leaf peel is placed in a concentrated salt solution, the purple-coloured protoplast shrinks away from the cell wall. This process is called:
   a) Deplasmolysis
   b) Imbibition
   c) Plasmolysis
   d) Guttation

10. Which test would you perform to detect the presence of starch in a plant extract, and what is the positive result?
    a) Benedict's test; Red precipitate
    b) Biuret test; Violet colour
    c) Iodine test; Blue-black colour
    d) Sudan III test; Orange colour

Answer Key:

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

Study these notes carefully, focusing on the distinguishing features and comparative aspects, as these are frequently tested areas. Good luck with your preparation!