Revision: Class 11 >> Morphology of Flowering Plants NEET (UG) Morphology of Flowering Plants

• A flower is a modified shoot wherein the shoot apical meristem changes to a floral meristem. Internodes do not elongate and the axis gets condensed.
• The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. The arrangement of flowers on the floral axis is termed inflorescence.

The pattern of ovule arrangement in the ovary is called placentation. 

Individual members of the perianth are called tepals.

A circular arrangement of floral organs at the same level on the thalamus is called a whorl.

The swollen terminal part of the pedicel on which all floral whorls are arranged is called the thalamus or receptacle.

When calyx and corolla are not differentiated, the floral envelope is called the perianth.

A modified, compressed reproductive shoot of angiosperms bearing sepals, petals, stamens, and carpels, meant for sexual reproduction, is called a flower.

A state of metabolic inactivity in mature seeds where germination does not occur even under seemingly favourable conditions.

Seed is defined as a fertilized mature ovule which possesses an inactive embryo and reserve food for its further development.

• Superior ovary Flowers with a superior ovary structure have the gynoecium at the top and the remaining floral components positioned underneath it.
• This arrangement of flowers is referred to as hypogynous. Mustard and brinjal are two examples.

• Morphology is the study of external features of organisms, especially plants.
• Adaptation refers to structural or functional changes that help organisms survive and reproduce in their environment.
• Flowering plants (angiosperms) show great variation in size, shape, structure, and habitat.
• Basic parts of angiosperms include roots, stems, leaves, flowers, and fruits.
• Plants have two main systems: root system (underground) and shoot system (above ground), with modifications for functions like storage, protection, and climbing.

• Root: Underground part of plant, develops from the radicle of embryo.
• Types of roots: Tap root (dicots), fibrous root (monocots), adventitious roots (from other plant parts).
• Functions: Absorption of water and minerals, anchorage, storage of food, synthesis of growth regulators.
• Root cap: Protects the tender root apex and helps in soil penetration.
• Regions of root: Meristematic (cell division), elongation (increase in length), maturation (differentiation and root hairs).
• Root hairs: Help in absorption of water and minerals from soil.
• Modifications: Support (prop, stilt), respiration (pneumatophores), storage (carrot, radish, turnip).

• Stem: Aerial part of the plant, develops from the plumule and bears nodes and internodes.
• Structure: Has nodes (leaf origin), internodes (between nodes) and buds (terminal and axillary).
• Functions: Supports the plant body and conducts water, minerals, and food.
• Food storage modification: Rhizome (ginger), tuber (potato), bulb (onion), corm (Colocasia).
• Support modification: Stem tendrils help in climbing (grapevine, cucumber).
• Protection & propagation: Thorns for protection (Citrus, Bougainvillaea); runners and stolons for vegetative propagation (strawberry, mint).
• Photosynthesis modification: Flattened stems (cladodes) perform photosynthesis (Opuntia).

• Leaf: Lateral, green, flattened structure developing from the shoot apical meristem; the main organ for photosynthesis.
• Parts of a leaf: Leaf base, petiole, and lamina; an axillary bud is present in the axil.
• Types of leaves: Simple leaf (single blade, e.g., mango) and compound leaf (leaflets, e.g., neem, rose).
• Venation: Arrangement of veins; reticulate (dicots) and parallel (monocots).
• Phyllotaxy: Arrangement of leaves on the stem; alternate, opposite, and whorled.
• Functions: Photosynthesis, transport of water/food, and gas exchange.
• Modifications: Tendrils (climbing), spines (protection), pitcher (nutrition), hooks (support).

• Inflorescence = Arrangement of flowers on the floral axis.
• Racemose — Main axis continues to grow; flowers in acropetal order (bottom → top). Ex: Amaranthus, Mustard, Snapdragon.
• Cymose — Main axis terminates in a flower; limited growth; flowers in basipetal order (top → bottom). Ex: Calotropis, Cotton, Jasmine, Solanum.
• Flower = Modified shoot where the shoot apical meristem turns into a floral meristem; internodes do not elongate.
• Alternate phyllotaxy — One leaf per node, arranged alternately. Ex: China rose, Mustard.
• Opposite phyllotaxy — Two leaves per node, facing each other. Ex: Calotropis, Guava.
• Whorled phyllotaxy — More than two leaves per node, forming a circle. Ex: Alstonia.

• Flower: A modified shoot and the reproductive unit of angiosperms.
• Structure: Consists of four whorls—calyx, corolla (accessory), androecium, and gynoecium (reproductive).
• Types by sex: Flowers may be unisexual (male/female) or bisexual (both present).
• Symmetry: Actinomorphic (radial), zygomorphic (bilateral), or asymmetric.
• Based on floral parts: Flowers can be trimerous, tetramerous, or pentamerous depending on the number of parts.
• Position of ovary: Hypogynous (superior), perigynous (half inferior), epigynous (inferior).

• Fruit: Develops from the mature ovary after fertilisation and contains seeds.
• Parthenocarpic fruit: Formed without fertilisation, usually seedless (e.g., banana).
• Structure: Fruit consists of pericarp (wall) and seeds; pericarp may be dry or fleshy.
• Pericarp layers: In fleshy fruits, it is divided into epicarp (outer), mesocarp (middle), and endocarp (inner).
• Drupe fruit: Develops from a monocarpellary superior ovary, usually one-seeded (e.g., mango, coconut).
• Types of fruits: True fruits develop from the ovary (mango, coconut); false fruits develop from other floral parts (apple, strawberry, pineapple).

• Seed is the fertilised ovule and final product of sexual reproduction in angiosperms.
• It consists of seed coat, cotyledons and embryo axis; food is stored mainly in cotyledons or endosperm.
• Seeds may be albuminous (endosperm present) or non-albuminous (endosperm absent); perisperm may persist in some seeds.
• Dormancy and dehydration help seeds survive adverse conditions and allow long-term storage.
• Seeds ensure dispersal, protection, nourishment of embryo, genetic variation and agricultural sustainability.

• Seed coat: Consists of two layers—testa (outer) and tegmen (inner).
• Hilum: A scar on the seed coat showing the point of attachment to the fruit.
• Micropyle: A small pore present above the hilum helps in water absorption.
• Cotyledons: Two fleshy cotyledons present, storing reserve food material.
• Embryo: Contains an embryonal axis with radicle and plumule at opposite ends.
• Endosperm: May be present (e.g., castor) or absent (e.g., bean, gram, pea) in mature seeds.

• Monocot seed: Usually endospermic, with endosperm storing food (except orchids).
• Endosperm: Large and bulky, separated from the embryo by a protein-rich aleurone layer.
• Embryo: Consists of a single cotyledon called the scutellum and a short embryonal axis.
• Cotyledon: Only one large, shield-shaped cotyledon present.
• Radicle and plumule: Radicle is enclosed in the coleorhiza, and plumule in the coleoptile.
• Seed structure: The seed coat is often fused with the fruit wall, and the embryo lies at one side of the endosperm.

• A semi-technical description is a systematic way of describing plants based on morphological features.
• The description follows an order: habit → vegetative parts (root, stem, leaves) → floral parts.
• Floral formula uses symbols like Br (bract), K (calyx), C (corolla), P (perianth), A (androecium), G (gynoecium).
• Symbols also indicate symmetry (⊕ actinomorphic, % zygomorphic) and sex of flower (male, female, bisexual).
• Fusion is shown by brackets and adhesion by a line above symbols in the floral formula.
• A floral diagram shows the number, arrangement, and relationship of floral parts.

• Solanaceae is known as the potato family, widely distributed in tropical and temperate regions.
• Vegetative features: Plants are mostly herbs or shrubs; the stem is herbaceous, branched, and may be underground (potato).
• Leaves: Alternate, simple, exstipulate, with reticulate venation.
• Inflorescence and flower: Inflorescence is solitary or cymose; flowers are bisexual and actinomorphic.
• Floral parts: Calyx and corolla are 5 united parts; 5 stamens (epipetalous).
• Gynoecium and fruit: Bicarpellary, superior ovary; fruit is a berry or capsule, with many seeds.
• Economic importance: Includes food (potato, tomato), spice (chilli), medicines, tobacco, and ornamentals.

• Malvaceae is known as the cotton or shoe-flower family with mostly herbaceous or woody plants.
• Leaves and stem: Leaves are alternate, simple, stipulate, with palmate venation; the stem may be erect and mucilaginous.
• Flower: Flowers are bisexual, actinomorphic, and pentamerous, often with an epicalyx present.
• Calyx and corolla: Calyx is 5, fused; corolla has 5 free, large, showy petals.
• Androecium: Numerous stamens, monadelphous, forming a staminal tube; anthers monothecous.
• Gynoecium: Pentacarpellary, syncarpous, with a superior ovary and axile placentation.
• Fruit and importance: Fruit is a capsule; it includes cotton (fibre), lady’s finger (food), Hibiscus (ornamental), and medicinal plants.

• Cruciferae (Brassicaceae) is the mustard family, mostly consisting of herbaceous plants.
• Stem and leaves: Stem is erect and herbaceous; leaves are alternate, simple or lobed, without stipules.
• Inflorescence: Usually raceme, with flowers arranged along a central axis.
• Flower: Typically bisexual and actinomorphic, with four sepals and four petals arranged in cross shape.
• Androecium: Six stamens (4 long + 2 short) showing tetradynamous condition.
• Gynoecium and fruit: Bicarpellary, superior ovary; fruit is silique or silicle with many seeds.
• Economic importance: Includes vegetables (cabbage, cauliflower), oilseeds (mustard), spices, and ornamentals.

• Fabaceae (Leguminosae) is the pea/bean family, including important pulse plants.
• Vegetative features: Plants may be herbs, shrubs, or trees with root nodules (Rhizobium) for nitrogen fixation.
• Leaves and stem: Leaves are alternate, pinnately compound, with stipules and pulvinate leaf bases; the stem may be erect or a climber.
• Inflorescence and flower: Inflorescence is racemose; flowers are bisexual and zygomorphic.
• Corolla: Papilionaceous (butterfly-shaped) with standard, wings, and keel arrangement.
• Androecium and gynoecium: 10 stamens (diadelphous); ovary superior, monocarpellary with many ovules.
• Fruit and importance: Fruit is a legume; it includes pulses (pea, gram), oils (groundnut), fibres, dyes, and medicines.

• Compositae (Asteraceae) is the sunflower family, one of the largest families of angiosperms.
• Stem and leaves: Plants are mostly herbaceous, stems may be erect, and leaves are usually alternate and simple or compound.
• Inflorescence: Characteristic capitulum (head) with many small flowers surrounded by bracts.
• Types of flowers: Two types present – ray florets (peripheral, zygomorphic) and disc florets (central, actinomorphic).
• Floral parts: Calyx modified into pappus (for dispersal), corolla fused, and usually 5 stamens.
• Fruit: Cypsela (achene-like), often dispersed by wind with help of pappus.
• Economic importance: Includes sunflower (oil), lettuce (food), medicinal plants, ornamentals, and weeds.

• Graminae (Poaceae) is the grass family, including important cereal crops like wheat, rice, and maize.
• Stem: Usually hollow and jointed (culm), herbaceous and unbranched.
• Leaves: Alternate, with sheath, blade, and ligule, showing parallel venation and no stipules.
• Flowers: Small, arranged in spikelets, with bracts called lemma and palea; perianth reduced to lodicules.
• Reproduction: Mostly wind-pollinated with feathery stigmas; flowers usually bisexual.
• Fruit: Caryopsis (grain), a single-seeded fruit where pericarp is fused with seed coat.
• Economic importance: Major source of food (cereals), fodder, biofuel, and erosion control.