Important Notes For NEET Biology – Morphology of Flowering Plants

The Root

Types of Root:

1. Tap root: Primary root formed by the elongation of the radicle, bearing secondary and tertiary roots, common in dicot plants (e.g., gram, mustard).
2. Fibrous root: Found in monocotyledons, with a large number of roots originating at the base of the stem (e.g., rice, wheat).
3. Adventitious root: Roots that arise from parts other than the radicle (e.g., grass, banyan tree, maize).

Modification of the Root:

1. For storage: Examples include taproots like carrot and turnip, and adventitious roots like sweet potato.
2. For support: Examples include prop roots of the banyan tree and stilt roots of maize and sugarcane.
3. For aeration: Pneumatophores in mangroves help in respiration by growing upwards above the ground (e.g., Rhizophora).
4. For nitrogen fixation: Root nodules in leguminous plants.

The Stem

• The plumule develops into the stem.
• The node is the part of the stem bearing leaves, and the internode is the part between two nodes.

Modification of the Stem:

1. Underground Stem: Helps plants survive unfavorable conditions.
   • Rhizome: Runs parallel to the ground (e.g., ginger, banana).
   • Tuber: End part gets swollen (e.g., potato).
   • Corm: Grows vertically below the ground (e.g., colocasia).
   • Bulb: Stem is reduced and surrounded by scaly leaves (e.g., garlic, onions).
2. Stem Tendrils: Coiled structures that support the plant (e.g., grapes, cucumber).
3. Thorn: Protects the plant from grazing animals (e.g., Bougainvillea, citrus).
4. Subaerial Weak Stem: Includes offsets, suckers, runners, and stolons.
5. Aerial Modification: Phylloclades in xerophytic plants (e.g., Euphorbia, Opuntia).

The Leaf

• Leaves originate from the apical meristem of a shoot.
• A typical leaf consists of a leaf base, lamina, and petiole.

Types of Venation:

1. Reticulate: Network of veins present, common in dicotyledons.
2. Parallel: Veins run parallel to each other, common in monocotyledons.

Types of Leaves:

1. Simple: Lamina is complete with no deep incisions.
2. Compound: Lamina is divided into leaflets.
   • Pinnately Compound: Leaflets are present on a common axis (e.g., Neem).
   • Palmately Compound: Leaflets are attached at the petiole tip (e.g., silk cotton).

Phyllotaxy (Arrangement of Leaves):

1. Alternate: Single leaf at each node (e.g., Hibiscus, Brassica).
2. Opposite: Pair of leaves at each node (e.g., Psidium guajava, Calotropis).
3. Whorled: More than two leaves arise at a node (e.g., Alstonia).

Modification of Leaves:

1. Tendrils: Long thread-like structures for support (e.g., peas).
2. Spine: Reduced water loss in xerophytic plants (e.g., cactus, aloe).
3. For Storage: (e.g., garlic, onion).
4. Phyllodes: Petiole modified to form a leaf-like structure (e.g., Acacia).
5. Pitcher: Modified leaf for trapping insects (e.g., pitcher plant).

Inflorescence

• Arrangement of flowers around the floral axis.

Types of Inflorescence:

1. Racemose: Main axis grows indefinitely with flowers in acropetal succession (e.g., raceme, spike, umbel).
2. Cymose: Main axis terminates in a flower with limited growth, flowers in basipetal order (e.g., monochasial, dichasial cyme).

Special Types:

1. Verticillaster: Sessile flowers arranged in dichasial cyme (e.g., Ocimum, Salvia).
2. Cyathium: Involucre of bracts forms a cup shape (e.g., Euphorbia).
3. Hypenthodium: Both male and female flowers in a cavity (e.g., Fig).

The Flower

• Consists of four whorls: calyx, corolla, androecium, and gynoecium.

Flower Symmetry:

1. Actinomorphic: Radially symmetrical (e.g., chilli, datura).
2. Zygomorphic: Divisible into two equal parts in one vertical plane (e.g., Cassia, pea).

Types of Flowers Based on Ovary Position:

1. Hypogynous: Gynoecium above all other parts (e.g., brinjal, china rose).
2. Perigynous: Gynoecium at the same level as other parts (e.g., peach, plum).
3. Epigynous: Gynoecium enclosed by the thalamus (e.g., guava, cucumber).

Parts of a Flower:

1. Calyx: Outermost whorl made of sepals.
2. Corolla: Bright-colored petals.
3. Androecium: Male reproductive part with stamens.
4. Gynoecium: Female reproductive part with carpels.

Placentation (Arrangement of Ovules in Ovary):

1. Marginal: (e.g., pea).
2. Axile: (e.g., lemon, china rose).
3. Parietal: (e.g., Argemone, mustard).
4. Free Central: (e.g., Primrose, Dianthus).
5. Basal: (e.g., marigold, sunflower).

The Fruit

• Matured and ripened ovary post-fertilization.
• Parthenocarpic fruits are formed without fertilization (e.g., pineapple).

Parts of a Fruit:

• Seed and pericarp, with three layers: epicarp, mesocarp, and endocarp.

The Seed

• Ovule develops into a seed post-fertilization.

Dicotyledonous Seed vs. Monocotyledonous Seed:

• Dicot: Two cotyledons, seed coat with testa and tegmen, non-endospermic.
• Monocot: One cotyledon (scutellum), endospermic with bulky food storage, includes aleuron layer.

These notes encompass the essential concepts of the morphology of flowering plants, vital for NEET Biology preparation.

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