Plants can be classified as herbs, shrubs, or trees based on stem form and size. Herbs have soft stems and few branches, while shrubs have short woody stems and many branches near the base. Trees have thick woody trunks and branches in the upper parts. All plants have root and shoot systems, with roots absorbing water and minerals from soil and shoots growing above ground. Leaves perform photosynthesis, respiration, and transpiration. Flowers contain reproductive parts that develop into fruits after pollination. Roots and stems undergo various modifications to store food, climb, or reproduce.

1. Types of plants
▪ Plants can be broadly classified into herbs, shrubs and trees based on the form and size of their
stem.
▪ Apart from these, there are climbers and creepers, which have weak stem.
Herbs
▪ They are small plants that have a soft, green stem.
▪ They have a few branches.
▪ Grass, coriander, mint, rice, wheat and tomato are examples of herbs.
Shrubs
▪ They have a short, thin, woody stem.
▪ They have many branches grows from or near the base of the stem.
▪ They appear bushy.
▪ The hibiscus, rose and lime are examples of shrubs.
Trees
▪ They are tall and have a thick, woody trunk.
▪ They have many branches grows from the upper parts of stem.
▪ The mango, banyan and gulmohar are example of trees.
Parts of a plant
All the plants have two main parts, they are
1. Root system: Parts of the plant that grows in the soil is called the root system.
2. Shoot system: Parts of the plant that grows above the soil is called shoot system.
Root system:
▪ The small root that developed from a seed after the germination is called radicle. The radicle forms
the primary root.
▪ Thin, thread-like structures that are present on the surface of the roots called root hairs. Root hairs
absorb water and mineral from the soil.

2. Type of Root system:
▪ There are two types of root systems, they are
1. The taproot system
2. The fibrous system
The taproot system:
• The main root, the branch toots and the root hairs form the taproot system.
• The radicle becomes the main taproot.
• The branch roots also called secondary root grows from the main taproot.
• The root hairs present on the surface of the roots.
• Plants like the mango, apple and plum have the taproot system.
The fibrous system:
• A cluster of thin, fibre-like roots developed from a common point at the base of the stem without
any primary root.
• All the roots have approximately the same length and thickness.
• Plants like grass, wheat and bamboo have the fibrous root system.
Function of roots:
▪ Roots fix the plant to the soil.
▪ Root hairs help the plant to absorb water and minerals from the soil.
▪ Some plants store food in their roots.
▪ Some plants reproduce through roots.
▪ Roots also hold soil and prevents it from being eroded by wind or water.
Roots Modification:
The structure and appearance of the roots are modified in some plants to carry out special function
❖ Storing food:
• Some roots are modified to store food. Carrot, radish, beetroot and store their food in main taproot
and the sweet potato and tapioca store their food in secondary root.

3. ❖ Support:
• Prop roots – These roots develop from the branches of the tree, hang downwards, and penetrate
into the ground thereby supporting the tree.
Example: Roots of the banyan tree and sugarcane plant
• Clasping roots – These roots develop from the stem of the climber like the money plant
Example: money plant and pepper plant.
❖ Breathing:
• Pneumatophores – A specialized root that grows upwards out of the water or mud to reach the
air and obtain oxygen for the root systems of trees that live in swampy or tidal habitats.
Example: mangrove trees have such breathing roots.
❖ Nitrogen fixation:
• Root nodules – A swelling structure on a root of a leguminous plant, containing nitrogen-fixing
bacteria are called root nodules. Bacteria in this root nodules convert the nitrogen in the air into
compound that the plant can use.
Example: pea and bean have root nodules.
Q. Which bacteria lives in the root nodules of leguminous plants?
Ans: Rhizobium is the nitrogen-fixing bacteria living in leguminous plants
❖ Reproduction:
• Suckers – The roots send out shoots called suckers which can grow into new plant.
Example: Cherry and Plum trees reproduced through suckers.

4. The Steam
▪ The plumule is the second part that develops from the germinating seed. It grows upwards and
becomes the main stem of the plant.
Function of the Steam
▪ The stem stands straight and bears the other parts of the shoot.
▪ It holds the leaves up to the light.
▪ It holds the flowers and fruits in positions suitable for pollination and seed dispersal.
▪ It transports water and food between the roots and the rest of the plant.
▪ Sone plants store food in the stem.
▪ Some plants reproduce through their stem.
Stem Modification
Storing food:
▪ Some plants like the ginger, potato, and turmeric store their food in the stem.
Support
▪ The stems have spirally coiled structures called tendrils. They help the plant to climb.
▪ Some plant like the bean and morning glory climbs around a support without any special structure.
Photosynthesis
▪ In plant like cactus, the stem contains chlorophyll and carries out photosynthesis.
▪ Stem also store water.
Reproduction
▪ Runner- a thin, long, weak stem that grows horizontally along the ground called runner.
▪ They produce new shoots and roots from points on the stem called nodes.
▪ In the ginger, banana and canna lily, the stem is modified into a thickened structure called a rhizome
from which new plant can grow.
Structure of a Leaf
▪ The leaves arise from the stem at points called nodes. The part of the stem between two nodes is
called internode.
▪ The broad, flat portion of the leaf is known as the lamina or leaf blade. The leaf tip is known as the
apex and the edge of the lamina is called the leaf margin. The leaf margin may be smooth, toothed or
lobed.
▪ The lamina is attached to the stem by the petiole. The petiole extends through the center of the lamina
called midrib. The veins arise from either side of the midrib.
▪ The arrangement of veins in the leaf is known as the venation of the leaf. There are two types of
venations, reticulate venation and parallel venation.
▪ When the veins form a network, such venation is known as reticulate venation.
▪ When the veins run parallel to one another, such venation is known as parallel venation.

5. Function of Leaves
The leaves carry out three main functions in plants
▪ Photosynthesis: the photosynthesis is a process by which green plants synthesis organic food
(carbohydrate) from carbon dioxide and water using solar energy by chlorophyll pigment.
Chlorophyll is the green substance found in leaves that traps the energy in sunlight.
carbon dioxide + water −
Chlorophyll
sunlight
→ food + oxygen
▪ Respiration: Plants take in oxygen and release carbon dioxide during respiration. Respiration takes
place throughout the day in every part of the plant.
food + oxygen − − − −→ carbon dioxide + water + energy
▪ Transpiration: The process by where plants get rid of excess water in the form of water vapour
through the stomata in leaves is called transpiration.
▪ Optimum transpiration helps in proper growth of plants.
▪ It keeps the plant cool.
▪ Transpiration helps in the conduction of water and minerals to different parts of the plants.
Modification of Leaves
▪ Support
▪ Storing food
▪ Trapping food
▪ Reproduction
▪ Self-defense:

6. Structure of flower
▪ The stalk of the flower is called pedicel.
▪ The outermost layer consists of small, green leaf like structures called sepals. The sepals
cover and protect the flower when it is a bud.
▪ The most colour full part inside the sepals is called petals.
▪ The male parts of a flower inside the petals are called stamens. Each stamen has stalk called
the filament, with a box-like structure on top called the anther. The anther contains powdery
particles called pollen grains.
▪ The female part of a flower at the center is called pistil. The pistil has three parts.
• Ovary: Ovary is attached to the base of the flower and contains the egg cells called ovules.
• Stigma: The top of the pistil is the stigma which is sticky.
• Style: The ovary and stigma are connected through a tube-like structure called the style.

7. Pollination
▪ The transfer of pollen grains from the anther to the stigma is called pollination.
▪ There are two types of pollination.
• Self-pollination
• Cross-pollination
▪ Self-pollination: The transfer of pollen grains from the anther to the stigma of the same flower, or
another flower of the same plant is called self-pollination.
▪ Cross-pollination: The transfer of pollen grains from the anther to the stigma of a flower on another
plant is called cross-pollination.
Fruit formation
▪ After the pollination the ovules develop and become seeds. The sepals, petals and stamens fall off.
The ovary starts to store food and swells up to form the fruit. The fruit protects the seeds and helps
in their dispersal.
Importance of Pollination
▪ Pollination helps to maintain genetic diversity in a population and develops adequate fruits for the
dispersal of seeds.
▪ They produce enough seeds for dispersal and propagation.
▪ The ecological functioning of the earth is enhanced by pollination and the terrestrial ecosystems are
through the pollinators.
How will you show that roots absorb water and transport it up the stem?
▪ Take three similar beakers and level them A, B, C. Add equal amounts of water to each beaker. Add a
few drops of red ink to the beaker C. Take two small plants and place them in beakers B and C with
the roots completely covered by water. Pour a teaspoonful of oil into each beaker to stop the water
from evaporating.
▪ After 24 hours we will see that the level of water in beakers B and C has fallen. This shows that the
roots have absorbed the water in the beakers.
▪ Make a transverse cut across the root and the stem of the plant in beaker C. we will see red dots in
both the root and the stem. Also make a longitudinal cut along the length of the plant. We will see
red lines. The lines show the path along which the water in the beaker moves along the stem after
being absorbed by the roots.
A B C