Morphology of Flowering Plants class 11th

Morphology

Morphology is the branch of biology that deals with the external structure or form of living organisms. In plants, morphology helps us understand the visible parts of a plant and their functions.

Morphology: Study of external features of plants.
Focus: Root, stem, leaf, inflorescence, flower, fruit, and seed.

Importance of Morphology in Flowering Plants:

1. ✅ Helps in the identification and classification of plants.
2. ✅ Useful in understanding adaptations to different environments.
3. ✅ Aids in taxonomy – grouping plants based on similarities and differences.
4. ✅ Helps in crop improvement and plant breeding.

Flowering Plants

Flowering plants, scientifically called Angiosperms, are the most advanced and diverse group of plants. They are called "flowering" because their most distinguishing feature is the presence of flowers, which are specialized for sexual reproduction.
Angiosperms produce seeds enclosed in fruits, unlike gymnosperms (naked seeds).
Flowering plants have two main systems:
Root system – Underground, anchors the plant and absorbs water/minerals.
Shoot system – Above ground, includes stem, leaves, flowers, and fruits.

Diversity in Flowering Plants:

Found in almost every habitat — land, water, desert, forest.

Range from tiny herbs (e.g., Lemna) to giant trees (e.g., Eucalyptus).

Two major groups:

Monocotyledons (Monocots) – 1 cotyledon in seed (e.g., grasses, maize)

Dicotyledons (Dicots) – 2 cotyledons in seed (e.g., pea, mango)

1. The Root

The root is the underground, non-green part of a plant that grows downward into the soil. It anchors the plant, absorbs water and minerals, and stores food in some cases.

Roots are usually non-photosynthetic and positive geotropic (grow toward gravity) and hydrotropic (grow toward water).

Origin of Root:

The root originates from the radicle of

the embryo (during seed germination).

It forms the primary root (main root), which gives rise to lateral roots.

Types of Root Systems:

1. Tap Root System

Develops from radicle.
Main root grows deep with lateral branches.
Found in dicot plants.
Example: Mango, Mustard

2. Fibrous Root System

Radicle is short-lived, replaced by thin, thread-like roots.
All roots arise from the base of the stem.
Found in monocot plants.
Example: Wheat, Grass

3. Adventitious Root System

Roots develop from parts of the plant other than the radicle (like stem or leaves).
Can be in both monocots and dicots.
Example: Maize, Banyan tree, Money plant

Regions of the Root:

1. Root Cap – Protects the root tip.

2. Region of Cell Division – Actively dividing cells behind the root cap.

3. Region of Elongation – Cells elongate and increase root length.

4. Region of Maturation – Cells differentiate; root hairs are formed for absorption.

2. The Stem

The stem is the aerial, ascending part of the plant that arises from the plumule of the embryo. It grows upward, supports branches, leaves, flowers, and fruits, and helps in conduction of water, minerals, and food.

It is usually green (in young stages) and photosynthetic.

Key Characteristics of a Stem:

Develops from the plumule of the embryo.

Grows away from gravity (negatively geotropic).

Bears nodes (points where leaves arise) and internodes (the space between two nodes).

Can have buds – terminal (apical) or axillary.

Typically erect, but may be modified for various functions.

Functions of the Stem:

1. Supports leaves, flowers, and fruits.

2. Transports water and minerals (via xylem) and food (via phloem).

3. Stores food (in some plants).

4. In some cases, helps in vegetative propagation.

5. May be modified for climbing, protection, or photosynthesis.

Types of Stem:

1. Herbaceous Stems – Soft and green (e.g., Mustard)

2. Woody Stems – Hard and brown (e.g., Mango, Neem)

Common Stem Modifications (brief preview):

Underground stems – for storage (e.g., Potato, Ginger)

Sub-aerial stems – for spreading and propagation (e.g., Grass, Strawberry)

Aerial stems – for support or protection (e.g., Tendrils in cucumber, Thorns in Bougainvillea)

3. The leaf

The leaf is a green, flattened, lateral outgrowth of the stem or its branches. It is born at the node, develops from the axil of a bud, and is photosynthetic in nature.

It is often called the “kitchen of the plant” because it is the main site of photosynthesis.

Key Features of a Typical Leaf:

1. Leaf Base – Attaches the leaf to the stem.

2. Petiole – The stalk that connects the leaf blade to the stem.

3. Lamina (Leaf Blade) – The broad, green part of the leaf where photosynthesis takes place.

Main Functions of a Leaf:

Photosynthesis – Food production using sunlight.
Transpiration – Loss of water vapor through stomata.
Gas Exchange – Oxygen and CO₂ exchange via stomata.
May get modified for storage, protection, support, or reproduction.

Leaf Origin and Arrangement:

Arises from shoot apical meristem.
Leaf is exogenous in origin (grows from the surface).
Found at nodes, and arranged in specific patterns (phyllotaxy).

Important Terms:

Phyllotaxy – The arrangement of leaves on the stem/branch:

Alternate (e.g., Mustard)
Opposite (e.g., Guava)
Whorled (e.g., Alstonia)

Venation – Arrangement of veins in the lamina:

Reticulate (net-like, in dicots)
Parallel (in monocots)

4. The Inflorescence

Inflorescence is the arrangement of flowers on the floral axis (peduncle). Instead of being solitary, flowers are often grouped to form a cluster, which enhances the chances of pollination and reproduction.

This cluster of flowers is called an inflorescence, and it follows specific patterns in different plant species.

Importance of Inflorescence:

Increases pollination efficiency.
Makes the plant more attractive to pollinators (like insects, birds, etc.).
Helps in plant classification and identification.

Types of Inflorescence:

1. Racemose Inflorescence

The main axis continues to grow indefinitely.

Flowers are borne laterally in an acropetal order (older flowers at the base, younger toward the top).

Example: Mustard, Radish, Amaranthus

2. Cymose Inflorescence

The main axis ends in a flower (growth is limited).

Flowers are borne in a basipetal order (older flowers at the top, younger at the base).

Example: Jasmine, Ixora

Special Types of Inflorescence:

1. Hypanthodium – Found in fig (Ficus), flowers are inside a hollow, fleshy receptacle.

2. Cyathium – Found in Euphorbia, a cup-like structure contains male and female flowers.

3. Verticillaster – Found in Ocimum (Tulsi), a cluster of flowers in leaf axils.

5. The flower

A flower is the reproductive part of an angiosperm (flowering plant). It is a modified shoot, specialized for sexual reproduction, and develops into fruits and seeds after fertilization.

It is often colorful and scented to attract pollinators like bees and butterflies.

Flower as a Modified Shoot:

Internodes are condensed.

Leaves are modified into floral organs.

It arises from the floral bud, often in

the axil of a leaf or at the tip of a stem.

Parts of a Typical Flower:

A typical flower is attached to the plant by a pedicel (stalk) and has four floral whorls arranged in concentric circles:

1. Calyx – Outermost whorl; made of sepals (usually green, protects the bud)

2. Corolla – Second whorl; made of petals (usually colored, attracts pollinators).

3. Androecium – Third whorl; male reproductive organ, made of stamens (anther + filament).

4. Gynoecium – Innermost whorl; female reproductive organ, made of carpels (ovary, style, stigma).

Types of Flowers:

Complete Flower – Has all 4 whorls (e.g., Datura).
Incomplete Flower – One or more whorls are missing (e.g., Corn).
Bisexual (Perfect) – Has both androecium and gynoecium (e.g., Hibiscus).
Unisexual – Has either androecium or gynoecium (e.g., Papaya).

Functions of a Flower:

Reproduction – Site of pollination, fertilization, and formation of seeds/fruits.

Attracts pollinators – Through color, nectar, and fragrance.

Ensures species continuation – Through seed production and dispersal.

6. The fruit

A fruit is a mature or ripened ovary of a flower that develops after fertilization. It encloses the seeds and often helps in their dispersal.

In some cases, fruits may also develop without fertilization — these are called parthenocarpic fruits (e.g., banana).

Parts of a Fruit:

A typical fruit has two main parts:

1. Pericarp – The fruit wall derived from the ovary wall.

It may be divided into:

Epicarp (outer layer)
Mesocarp (middle fleshy layer)
Endocarp (inner layer surrounding the seed)

2. Seed – Developed from the ovule.

Types of Fruits:

1. True Fruit

Develops only from the ovary.
Example: Mango, Tomato

2. False Fruit

Develops from the ovary plus other floral parts (like thalamus).
Example: Apple, Strawberry

3. Parthenocarpic Fruit

Develops without fertilization, seedless.
Example: Banana

Classification Based on Origin:

Simple Fruit – From a single ovary (e.g., Mango)
Aggregate Fruit – From a flower with multiple free carpels (e.g., Strawberry)
Multiple Fruit – From an inflorescence, not a single flower (e.g., Pineapple)

7. The seed

A seed is the mature ovule formed after fertilization. It contains the embryo and serves as the unit of reproduction in flowering plants. The seed gives rise to a new plant upon germination.

It is one of the most important adaptations for survival and dispersal in terrestrial plants.

Basic Structure of a Seed:

A typical seed consists of:

1. Seed Coat – Protective outer layer:

Testa (outer coat)
Tegmen (inner coat)

2. Embryo – The baby plant:

Radicle (forms root)
Plumule (forms shoot)
Cotyledons (seed leaves, store food)

3. Endosperm (in some seeds) – Nutritive tissue that nourishes the embryo

Types of Seeds Based on Cotyledons:

1. Dicot Seeds

Have two cotyledons.
Example: Gram, Pea, Bean
May or may not have endosperm (often non-endospermic).

2. Monocot Seeds

Have one cotyledon (called scutellum in grasses).
Example: Maize, Rice, Wheat
Usually endospermic (endosperm present).

Functions of a Seed:

Stores food for the embryo.
Protects the embryo until germination.
Allows dispersal and survival under unfavorable conditions.
Ensures continuation of species.

8. Floral Formula

A floral formula is a symbolic representation of the structure of a flower using specific symbols and numbers. It gives a quick overview of the flower’s morphology — including the number, arrangement, and fusion of floral parts.

It is very important in NEET for analyzing floral structure without diagrams.