IMPORTANT TERMS

Root System      - The parts of the plant that remain under the ground, form the root system.     

Shoot System     - All parts of a plant that are above the ground, form the shoot system.         

Creepers            - Plants with weak stems that cannot stand upright and spread on the ground e.g.Grass.

Climbers             - Plants that take support on neighbouring structures and climb up. E.g. Moneyplant 

Tap Roots           - A single root comes out from the seed after germination; also known as true roots

Fibrous roots       - Roots which grow from the base of the stem and have a bushy appearance.

Venation             - The arrangement of veins in a leaf.

Parallel venation   - The veins run parallel to one another from the base to the tip of the leaf.

Reticulate venation  - The veins are arranged in a net-like pattern on both sides of the midrib.

Photosynthesis   - Process of making food by the plant using co2, water, chlorophyll and sunlight.

Transpiration      - Process by which plants release excess water in the form of water vapor through stomata.

Pollination         - Transfer of pollen grains from the anther to the stigma.

Node                 - Part of the stem from which leaves arise.

Internode           - The space between two nodes.

 

TYPES OF PLANTS

Based on their height, stems and branches, plants can be classified into three categories: Herbs, shrubs and trees.

• Herbs are small plants with green and tender stems. They are usually short and do not have many branches for e.g. Tomato, potato.
• Shrubs are taller than herbs and the stems of shrubs are hard but not very thick. E.g. Lemon.
• Trees are very tall and have hard and thick brown stem. The stems have branches in the upper part. E.g. Neem, mango, banyan etc.

FUNCTIONS OF ROOTS

• Preventing Soil Erosion - Roots help to bind the soil particles together, thereby preventing them from being carried away by water or wind.
• Anchoring the Plant - Roots hold the plants firmly into the soil, thereby serving as an anchor to the plants.
• Absorption of Nutrients from the Soil - They help plants to absorb water and nutrients from the soil.

ROOT MODIFICATIONS

Roots of some plants are modified to perform additional functions.

• For storage of food – Roots of some plants are modified for storage of food e.g. Radish, carrot.
• For multiplication - Roots of some plants develop into new plants e.g. Dahlia.
• For climbing - Some plants have climbing roots e.g. money plant, betel etc.
• For extra support - Roots of some plants give out extra roots e.g. Banyan, sugarcane.

 

PARTS OF A LEAF

Leaves arise at the nodes of the stems and have a characteristic shape and size. Leaves are green because of the presence of green pigment called chlorophyll.

• Lamina - The flat, green portion of the leaf is called lamina.
• Petiole - The part of a leaf by which it is attached to the stem is called petiole.
• Veins -   The parallel or net-like patterns on the leaves are called veins.
• Midrib -   It is the continuation of the petiole to form the central vein of the leaf.

FUNCTIONS OF A LEAF

• A leaf prepares food for the plants by the process of photosynthesis.
• Plants breathe with the help of their leaves. Tiny openings called stomata allow plants to exchange gases.
• Leaves lose water through the process of transpiration.

LEAF MODIFICATIONS

• Leaves of some plants are modified to form tendrils. They help plants to attach themselves to a support such as walls, fences, etc. e.g. grapes.
• Leaves of some plants are modified to form spines. They reduce the amount of water lost from the plant. e.g. cactus.

FUNCTIONS OF A STEM

The stem is a very important part of the plant.

• It provides support to the branches of the plant.
• It bears buds, leaves, flower and fruits.
• It carries water and minerals from roots to other parts of the plant.
• It carries prepared food from leaves to other parts of the plant.

 

STEM MODIFICATIONS

Stems of some plants are modified to perform special functions.

• For storage of water - Stems of some plants are modified to store water in them like Cactus.
• To manufacture food – Stems of some plants become leaf-like and prepare food e.g. cactus.
• For protection - Stems are modified as thorns or in the form of sharp prickles to protect them from being eaten by animals e.g. rose plant and bougainvillea.
• For storage of food - Stems are modified to store food e.g. Potato, onion.
• For support- Stems are modified for support e.g. grapes, passion flower etc.
• For multiplication of the plant – Stem cuttings of some plants grow into new plants e.g. Jasmine, rose etc.

 

PARTS OF A FLOWER

A flower is the reproductive organ of a plant. For a flower to develop into a fruit and form seeds, pollen grains must be transferred from its anthers to the stigma.

• Petals are colourful structures that surround the inner parts of a flower.
• The male reproductive part of a flower is called stamen. It has two parts: Anther and filament.
• Carpel (Pistil) is the female reproductive part of a flower. It has three parts: stigma, ovary and style.
• Sepals are the green leaf like structures at the base of the flower. They protect the flower during its development.

 

INTERESTING FACTS

• Stems prepare food in most desert plants like cactus.

• Sunflower is not a single flower but a group of flowers.

• Deserts plants have longer roots as they penetrate deep into the soil in search of water.

• In order to burn food and generate energy during night, plants take oxygen and release carbon dioxide just like human beings.

• The kind of roots a plant has can be identified by observing the venation.