PLANT SYSTEM

Science

INTRODUCTION
Botany, also known as plant science or plant biology, is a branch of biology that deals with the scientific study of plants. It includes the study of plant structure, growth, reproduction, metabolism, development, diseases, and evolution. Plants are essential for life on Earth as they provide oxygen, food, medicines, fibres, fuel, and maintain ecological balance.

CLASSIFICATION OF PLANTS
Plants can be classified in several ways based on structural, reproductive, and functional characteristics.

1. Based on Vascular Tissues
Vascular Plants:

These plants possess specialised conducting tissues called xylem and phloem.
Xylem transports water and minerals from roots to aerial parts.
Phloem transports prepared food from leaves to other parts of the plant.
Examples: Ferns, gymnosperms, angiosperms.

Non-Vascular Plants:

These plants lack specialised vascular tissues.
Water and nutrients move by diffusion.
Usually small and found in moist habitats.
Examples: Mosses, liverworts.

2. Based on Seed Formation
Seed-Bearing Plants:

Plants that reproduce through seeds.
Includes gymnosperms and angiosperms.

Spore-Bearing Plants:

Plants that reproduce by spores.
Examples: Ferns, mosses.

3. Based on Seed Covering
Angiosperms:

Flowering plants.
Seeds are enclosed within fruits.
Largest group of plants.
Examples: Mango, wheat, rose.

Gymnosperms:

Non-flowering plants.
Seeds are naked and not enclosed by fruits.
Examples: Pine, Cycas.

4. Based on Growth Habit
Grasses:

Plants with narrow leaves and hollow stems.
Often reproduce through rhizomes.
Examples: Wheat, rice.

Herbaceous Plants:

Soft stems.
Usually die at the end of the growing season.
Examples: Tomato, sunflower.

Woody Shrubs:

Hard stems with bark.
Shorter than trees.
Examples: Rose, hibiscus.

Trees:

Tall woody plants with a single main trunk.
Examples: Neem, mango.

PLANT MORPHOLOGY (PHYTOMORPHOLOGY)

Plant morphology is the study of the external structure and form of plants. It helps in identification, classification, and understanding adaptations of plants to different environments.
The concept was introduced by Johann Wolfgang von Goethe in the early 19th century.

PLANT ANATOMY (PHYTOTOMY)
Plant anatomy deals with the internal structure of plants, including tissues and cells.

MORPHOLOGY OF FLOWERING PLANTS (ANGIOSPERMS)

Angiosperms are the most advanced and diverse group of land plants with about 3.5 lakh species.
They are vascular plants with flowers as reproductive organs.
Seeds are enclosed within fruits.
They show a high degree of structural specialization.

ADAPTATION

Adaptation refers to any structural, physiological, or behavioural feature that enables an organism to survive and reproduce in its environment.
Example: Thick cuticle in desert plants to prevent water loss.

ROOT SYSTEM
The root is the underground part of the plant, developing from the radicle of the embryo.

Functions of Roots

Absorption of water and minerals from soil.
Anchorage and support to the plant.
Storage of reserve food.
Synthesis of plant growth regulators.
Respiration in some modified roots.

Types of Roots

Tap Root System:
Develops from radicle.
Main root persists and gives rise to lateral branches.
Found in dicot plants.
Examples: Gram, pea, mango.

Fibrous Root System:

Radicle is short-lived.
Many thin roots arise from the base of the stem.
Found in monocot plants.
Examples: Wheat, rice.

Adventitious Roots:

Roots arise from parts other than radicle.
Examples: Banyan, sugarcane, grass.

Modifications of Roots

For Support:
Prop roots – Banyan.
Stilt roots – Maize, sugarcane.

For Respiration:
Pneumatophores – Mangrove plants (Rhizophora).

For Storage:

Fusiform – Radish.
Conical – Carrot.
Napiform – Turnip.

SHOOT SYSTEM (STEM)

Stem is the aerial part of the plant developing from the plumule of the embryo.
It bears nodes, internodes, leaves, buds, flowers and fruits.

Functions of Stem

Supports aerial parts.
Conducts water, minerals, and food.
Photosynthesis in green stems.
Storage of food in some plants.
Vegetative propagation.

Modifications of Stem

For Food Storage:
Rhizome – Ginger.
Tuber – Potato.
Bulb – Onion.
Corm – Colocasia.

For Support:

Stem tendrils – Grapevine, cucumber.

For Protection:

Thorns – Bougainvillea, citrus.

For Vegetative Propagation:

Strawberry, mint, jasmine.

For Photosynthesis:

Flattened green stem – Opuntia.

LEAF

Leaves are thin, flattened, green organs attached to the stem.
They arise from nodes and are usually borne laterally.

Functions of Leaves

Photosynthesis.
Respiration.
Transpiration.
Storage of food and water.
Vegetative reproduction in some plants.

Modified Leaves

Spines – Cactus (protection).
Bracts – Bougainvillea.
Succulent leaves – Aloe.
Tendrils – Pea.
Scaly leaves – Onion.
Hook leaves – Bignonia.
Pitcher leaves – Pitcher plant (insectivorous).

FLOWER

A flower is the reproductive structure of angiosperms.
It is borne on a stalk called pedicel.
The swollen end is called thalamus or receptacle.

Whorls of Flower

Calyx – Sepals, protective.
Corolla – Petals, attraction.
Androecium – Male reproductive part (stamens).
Gynoecium – Female reproductive part (carpel).

Types of Flowers

Bisexual – Contains both androecium and gynoecium.
Unisexual – Contains either male or female parts.

FRUIT

Fruit is the ripened ovary formed after fertilization.
Parthenocarpic fruits develop without fertilization.

Structure of Fruit

Pericarp:
Epicarp – outer layer.
Mesocarp – middle layer.
Endocarp – inner layer.

Examples:

Mango – edible mesocarp.
Coconut – fibrous mesocarp.

Types of Fruits
Simple Fruits:

Develop from a single ovary.
Examples: Apple, tomato.

Aggregate Fruits:

Develop from multiple ovaries of a single flower.
Examples: Strawberry, raspberry.

Multiple Fruits:

Develop from ovaries of many flowers.
Examples: Pineapple, fig.

SEED

Seed is formed from fertilized ovule.
It consists of seed coat and embryo.
Embryo includes radicle, plumule, and cotyledons.
Seeds ensure propagation and survival of plant species.

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Subject: Science

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