NCERT Biology Class 11 - Chapter 5: Morphology of Flowering Plants - Notes

Learning Objectives

Understand the morphology of root, stem, leaf, flower, fruit, and seed
Learn different types of root systems, stems, and leaf modifications
Understand floral morphology and describe flowers using floral formula
Study the structure of different types of fruits and seeds

Key Concepts

Root

Tap root system: Found in dicots. Primary root develops from radicle. Fibrous root system: Found in monocots. Primary root is short-lived, replaced by adventitious roots. Modifications: Storage roots (carrot — conical, radish — fusiform, sweet potato — tuberous), Pneumatophores (breathing roots in mangroves like Rhizophora), Stilt roots (maize), Prop roots (banyan), Nodular roots (legumes with Rhizobium).

Stem

Develops from plumule. Bears nodes, internodes, buds. Modifications: Underground stems (rhizome — ginger; tuber — potato; bulb — onion; corm — colocasia), Sub-aerial stems (runner — grass; stolon — strawberry; offset — water hyacinth; sucker — chrysanthemum), Aerial stems (tendril — grapevine; thorn — Bougainvillea; phylloclade — Opuntia; cladode — Asparagus).

Leaf

Parts: Leaf base (hypopodium), petiole (mesopodium), lamina (epipodium). Venation: Reticulate (dicots) or parallel (monocots). Types: Simple (undivided lamina) or Compound (divided into leaflets — pinnately compound like neem; palmately compound like silk cotton). Phyllotaxy: Alternate (sunflower), Opposite (Calotropis), Whorled (Alstonia). Modifications: Tendrils (pea), spines (cacti), pitcher (Nepenthes), bladder (Utricularia), phyllode (Australian Acacia).

Flower

A modified shoot for reproduction. Parts: Calyx (sepals — protective), Corolla (petals — attract pollinators), Androecium (stamens = filament + anther; male part), Gynoecium (carpels = stigma + style + ovary; female part). Placentation: Marginal (pea), Axile (hibiscus, tomato), Parietal (mustard), Free central (Dianthus), Basal (sunflower).

Aestivation: Arrangement of sepals/petals in bud. Valvate (Calotropis), Twisted (China rose), Imbricate (Cassia), Vexillary/Papilionaceous (pea).

Fruit and Seed

Fruit: Ripened ovary. True fruit develops from ovary alone. False fruit (pseudocarp) develops from other floral parts also (e.g., apple — thalamus). Seed: Contains seed coat (testa, tegmen), embryo (radicle, plumule, embryonal axis), and endosperm (food storage in endospermic seeds). Dicot seed: two cotyledons (e.g., gram). Monocot seed: one cotyledon + scutellum + coleoptile + coleorhiza (e.g., maize).

Description of Important Families

Fabaceae (Pea family): Papilionaceous corolla, diadelphous stamens (9+1), marginal placentation. Formula: % ⚥ K(5) C1+2+(2) A(9)+1 G1. Examples: pea, gram, soybean.

Solanaceae (Potato family): Epipetalous stamens, axile placentation, bicarpellary ovary. Formula: ⊕ ⚥ K(5) C(5) A5 G(2). Examples: tomato, potato, tobacco, petunia.

Liliaceae (Lily family): Perianth 6 (tepals), trimerous flower, axile placentation. Formula: ⊕ ⚥ P3+3 A3+3 G(3). Examples: lily, tulip, onion, garlic, Aloe.

Summary

Flowering plants have well-defined morphological structures. Roots, stems, and leaves undergo various modifications for special functions. Flowers are reproductive structures with four whorls. Fruits develop from ovaries after fertilization. Seeds contain the embryo for the next generation. Families Fabaceae, Solanaceae, and Liliaceae have characteristic floral features.

Important Terms

Phyllotaxy: Arrangement of leaves on the stem
Placentation: Arrangement of ovules within the ovary
Aestivation: Arrangement of petals/sepals in a flower bud
Pneumatophores: Breathing roots in mangrove plants
Phylloclade: Flattened stem performing photosynthesis (e.g., Opuntia)
Epipetalous: Stamens attached to petals
Diadelphous: Stamens united in two bundles (9+1)
Pseudocarp: False fruit developing from parts other than ovary

Quick Revision

Tap root = dicots; Fibrous root = monocots
Potato = stem tuber; Sweet potato = root tuber
Onion = bulb (stem); Ginger = rhizome (stem)
Reticulate venation = dicots; Parallel = monocots
Fabaceae: papilionaceous, diadelphous, marginal placentation
Solanaceae: epipetalous, bicarpellary, axile placentation
Liliaceae: trimerous, perianth of tepals, axile placentation
Apple = false fruit (thalamus); Mango = true fruit (ovary)