Morphology of Flowering Plants

Introduction to Angiosperms

• Angiosperms (flowering plants) are characterized by three main features:
  • Presence of flowers
  • Seeds enclosed in fruits
  • Double fertilization resulting in the formation of a zygote and the triploid endosperm

Morphology

• Morphology: Study of the external structure and appearance of plants
• Parts of a plant visible externally (root, stem, leaf, flower, fruit, seed) fall under morphology
• Morphological features and adaptations of roots, stems, and leaves are discussed

Root Function and Modifications

Basic Functions

• Absorption of water and minerals
• Anchorage to ground
• Storage of food
• Synthesis of plant growth regulators (e.g., auxins)

Root Types and Modifications

• Tap root (Example: Mustard)
• Fibrous root (Example: Wheat)
• Adventitious root (Example: Banyan tree)
• Primary root produces secondary and tertiary roots; forms tap root system
• Adventitious roots arise from parts other than the radicle

Modified Roots

• Adaptations for special functions (storage, support, respiration)
• Storage roots (Examples: Carrot, Sweet potato)
• Prop roots (Example: Banyan tree)
• Pneumatophores for respiration (Example: Mangrove trees)

Stem Function and Modifications

Basic Functions

• Conduction of nutrients and water
• Storage of food
• Support
• Protection

Stem Types and Modifications

• Underground stems (Examples: Potato, Ginger, Turmeric)
• Tendrils for support (Examples: Watermelon, Grape vine)
• Thorns for protection (Examples: Citrus plants, Bougainvillea)
• Photosynthetic stems (Examples: Opuntia, Euphorbia)

Special Types

• Runner (Example: Grass, Strawberry)
• Stolon (Example: Mint)
• Offset (Example: Water Hyacinth)
• Sucker (Example: Pineapple)

Leaf Function and Morphology

Basic Structures

• Leaf base, Petiole, Leaf blade (lamina)
• Simple leaves have an undivided blade
• Compound leaves are divided into leaflets

Venation

• Parallel venation (Example: Monocots like Corn)
• Reticulate venation (Example: Dicots like Mango)

Leaf Arrangements

• Alternate (Example: Mustard, Sunflower)
• Opposite (Example: Guava)
• Whorled (Example: Alstonia)

Leaf Modifications

• Leaf tendrils (Example: Pea)
• Spines (Example: Cactus)
• Phyllode (Example: Acacia)
• Insect-trapping leaves (Example: Venus flytrap, Pitcher plant)

Inflorescence

• Arrangement of flowers on the floral axis
• Racemose inflorescence: Flowers bloom progressively, oldest at base, youngest at top
• Cymose inflorescence: Main axis terminates in a flower; flowers present in a basipetal manner

Flower Structure and Parts

Flower Basics

• Pedicel: The stalk of the flower
• Thalamus (Receptacle): Platform-like structure that supports floral parts
• Calyx: The outermost whorl, consisting of sepals
• Corolla: Made up of petals, generally colorful
• Androecium: The male reproductive part, consisting of stamens
• Gynoecium: The female reproductive part, consisting of carpels

Flower Symmetry

• Actinomorphic: Radial symmetry (Example: Mustard)
• Zygomorphic: Bilateral symmetry (Example: Pea)
• Asymmetry: No symmetry (Example: Canna)

Types of Flowers

• Unisexual: Either stamens (male) or pistils (female)
• Bisexual: Both stamens and pistils

Floral Diagram and Formula

• Floral diagram depicts flower structure
• Formula provides symbolic representation of flower structure:
  • Example: Br and k(5) c(5) A5+5 G(2)

Aestivation

• Valvate: Petals/Sepals just touch
• Twisted: Regular overlapping
• Imbricate: Irregular overlapping
• Vexillary: Largest petal overlaps two lateral petals which in turn overlap two smallest petals (Example: Pea)

Placentation

• Arrangement of ovules within the ovary
• Marginal (Example: Pea)
• Axile (Example: Tomato)
• Parietal (Example: Mustard)
• Free central (Example: Dianthus)
• Basal (Example: Sunflower)

Fruit

• Develops from the ovary after fertilization
• Pericarp: The wall of the fruit
  • Epicarp: Outermost layer
  • Mesocarp: Middle layer
  • Endocarp: Innermost layer
• Examples: Mango, Coconut

Seed

• Seed coat and embryo are the main components
  • Seed coat: Outer protective layer (Testa and Tegmen)
  • Embryo: Consists of radicle, plumule, and cotyledons
• Dicot: Two cotyledons (Example: Pea)
• Monocot: One cotyledon (Example: Corn)

Examples of Plant Families

Brassicaceae (Mustard Family)

• Tetramerous flowers
• Floral formula: k2+2 c4 A2+4 G2
• Example: Brassica (Mustard)

Fabaceae (Legume Family)

• Pentamerous flowers
• Floral formula: k(5) c1+2+(2) A9+1 G1
• Example: Pea, Soybean

Solanaceae (Potato Family)

• Pentamerous flowers
• Floral formula: k(5) c(5) A5 G(2)
• Example: Tomato, Potato, Chilli

Liliaceae (Lily Family)

• Characteristics: Presence of tepals, superior ovary
• Example: Lily

Conclusion

• Reviewed the morphology and structural organization of flowering plants
• Discussed various modifications and features of roots, stems, leaves, and flowers
• Examined key families and their unique structures