Morphology of Flowering Plants 🌵 - Biology Class 11th - Handwritten Notes 📖 [PDF]📚

Morphology is the study of the external features, forms, and structures of living organisms. In flowering plants (angiosperms), it deals with the study of different parts like root, stem, leaf, inflorescence, flower, fruit, and seed. Understanding morphology is essential for plant identification, classification, and economic uses.

Root

Characteristics

• Non-green, underground, positively geotropic.
• No nodes, internodes, or leaves.
• Functions: Anchorage, absorption of water and minerals, storage, conduction.

Types of Root System

1. Tap root system – arises from radicle (dicots, e.g., mustard).
2. Fibrous root system – arises from base of stem (monocots, e.g., wheat, rice).
3. Adventitious roots – arise from any part other than radicle (e.g., grass, banyan, maize).

Root Regions

1. Root cap – protective.
2. Region of meristematic activity – cell division.
3. Region of elongation – rapid cell enlargement.
4. Region of maturation – differentiation, root hairs.

Root Modifications

• Storage roots – carrot, radish, sweet potato.
• Prop roots – banyan.
• Stilt roots – maize, sugarcane.
• Respiratory roots – mangroves (pneumatophores).
• Climbing roots – betel, ivy.
• Photosynthetic roots – Tinospora.

Stem

Characteristics

• Ascending axis, usually aerial, phototropic.
• Bears nodes, internodes, branches, leaves, buds.

Functions

• Support, conduction, storage, vegetative propagation.

Stem Modifications

• Underground (for storage/vegetative propagation): Rhizome (ginger), Corm (Colocasia), Tuber (potato), Bulb (onion).
• Subaerial: Runner (grass), Stolon (jasmine), Sucker (mint), Offset (Eichhornia).
• Aerial: Tendrils (cucumber), Thorns (Bougainvillea), Phylloclade (Opuntia).

Leaf

Characteristics

• Green, flattened, borne at nodes, arises from axillary bud.
• Dorsiventral, exogenous origin, limited growth.

Parts

1. Leaf base (stipules may be present).
2. Petiole (leaf stalk).
3. Lamina (leaf blade).

Venation

• Reticulate – dicots (peepal).
• Parallel – monocots (wheat, rice).

Phyllotaxy (arrangement of leaves on stem)

• Alternate (china rose), Opposite (guava), Whorled (Alstonia).

Leaf Modifications

• Tendrils (pea), Spines (cactus), Storage (onion), Insectivorous (Nepenthes, Venus flytrap).

Inflorescence

Arrangement of flowers on floral axis (peduncle).

Types

Racemose (indeterminate)

• Main axis grows continuously, younger flowers at apex.
• Examples: Raceme (radish), Spike (wheat), Catkin (mulberry), Umbel (onion), Corymb (candytuft), Capitulum (sunflower).

Cymose (determinate)

• Main axis terminates in a flower, growth limited.
• Examples: Uniparous (hibiscus), Biparous, Multiparous.

Special

• Cyathium (Euphorbia), Hypanthodium (Ficus), Verticillaster (mint).

Flower

Characteristics

• Reproductive structure, modified shoot.
• Arises from floral buds.
• Essential whorls: Androecium (male), Gynoecium (female).
• Non-essential whorls: Calyx (sepals), Corolla (petals).

Symmetry

• Actinomorphic (radial, e.g., mustard).
• Zygomorphic (bilateral, e.g., pea).
• Asymmetric (e.g., canna).

Aestivation (arrangement of sepals/petals)

• Valvate, Twisted, Imbricate, Vexillary (pea).

Ovary Position

• Hypogynous (superior ovary, e.g., mustard).
• Perigynous (half inferior, e.g., rose).
• Epigynous (inferior ovary, e.g., guava).

Fruit

Definition: Mature ovary after fertilization, often with seeds.

Types

• True fruit: From ovary only (mango, tomato).
• False fruit: From ovary + other floral parts (apple, strawberry).

Classification

1. Simple: From single ovary (drupe – mango, berry – tomato).
2. Aggregate: From polycarpellary apocarpous ovary (custard apple).
3. Composite/Multiple: From inflorescence (pineapple, fig).

Seed

Definition: Mature ovule after fertilization.

Structure

• Seed coat (testa, tegmen).
• Embryo (radicle, plumule, cotyledons).
• Endosperm (in monocots).

Types

• Monocot seed – maize.
• Dicot seed – bean, pea.

Modification of Plant Parts

Plants modify their parts (root, stem, leaf) for special functions like storage, protection, support, reproduction, and photosynthesis.

Root Modifications

• Storage roots (carrot).
• Prop roots (banyan).
• Pneumatophores (mangroves).

Stem Modifications

• Underground: rhizome, tuber, bulb.
• Subaerial: runner, stolon, offset.
• Aerial: tendril, thorn, phylloclade.

Leaf Modifications

• Tendrils (pea).
• Spines (cactus).
• Insectivorous (Nepenthes).
• Succulent leaves (Aloe).