Reproduction in Plants - Class 5 Notes & Olympiad Questions

Reproduction in Plants

a) Reproduction is the natural process by which living things create more of their own kind.
b) Reproduction is really important for plants because it allows them to survive and spread in different environments.
c) While many plants reproduce by producing seeds, there are some plants that can also reproduce using different parts such as roots, stems, and leaves. It is called vegetative reproduction.

Reproduction Through Seeds

A seed is a special part of a plant that has the ability to grow into a whole new plant. When a seed starts to grow and develop into a plant, we call this process germination.

Structure of a Seed

A seed is made up of three important parts that help it grow into a plant. These parts are:

1. Embryo

a) The embryo is like the baby plant inside the seed.
b) As the seed matures, the embryo starts growing and developing into a seedling, which eventually becomes a full-grown plant.

2. Seed Coat

a) The seed coat is the tough and protective outer covering of the seed.
b) It acts like a shield, keeping the baby plant safe from harm and preventing water from escaping.

3. Food Store

a) The food store is the stored food that the parent plant provides for the growing embryo.
b) This stored food, usually in the form of starch, is stored in special seed leaves called cotyledons.
c) The cotyledons provide nutrients and energy to the growing embryo until it becomes big enough to make its own food through photosynthesis.

Germination

For a seed to germinate and start growing, it needs a few important things: water, air, and the right temperature.

a) Water helps the seed soften and swell up. This allows the embryo inside the seed to start growing.
b) Air is important because it contains the oxygen that the plant needs to carry out its functions. Without enough oxygen, the seed wouldn't be able to grow properly.
c) Lastly, the temperature needs to be suitable for the seed to germinate. Different plants have different temperature preferences, but generally, they need a warm and comfortable environment to start growing.

When a seed has all these conditions met—enough water, air, and suitable temperature—it can begin to germinate.

The seed will start to sprout and send out roots to anchor itself in the soil, and a shoot will grow upwards towards the sunlight. As the plant grows, it will develop leaves, stems, and eventually flowers or fruits, depending on the type of plant.

Vegetative Reproduction

a) Not all plants use seeds to reproduce. Some plants have unique ways of creating new plants using their different body parts like roots, leaves, and stems.
b) This special method of reproduction is called vegetative propagation or vegetative reproduction.
c) Vegetative propagation can be of two types: natural and artificial.

Natural Vegetative Propagation

This type of propagation happens in nature without any human intervention. Some common examples are:

1. Reproduction from Roots

a) Reproduction from roots is a type of vegetative propagation that some plants, like sweet potatoes, use to create new plants.
b) In the case of sweet potatoes, the actual part we eat is the root of the plant. This root is called a tuber.
c) When sweet potato tubers are cut into pieces and planted in the soil, they have the ability to give rise to new plants. Each tuber contains special buds called "eyes" that have the potential to grow into new shoots and roots.

2. Reproduction from Stems

a) Reproduction from stems is another type of vegetative propagation found in plants like potatoes, onions, ginger, and turmeric.
b) Specifically, these plants have underground stems called stem tubers, and they play a special role in creating new plants.
c) The stem tuber is swollen and contains many nodes or "eyes." Each eye has buds, which are small growth points that can develop into new shoots and roots.

3. Reproduction Through Leaves

a) Plants like the bryophyllum and begonia can reproduce through their leaves.
b) The notches on the bryophyllum leaves and fallen leaves of begonia plants have buds that can grow into new plants when they come in contact with the soil.

Artificial Vegetative Propagation

This type of propagation is performed by humans intentionally to create new plants. It involves specific techniques to separate and grow parts of the plant. Some common methods are:

1. Reproduction Through Cuttings

a) In this method, a mature stem from a parent plant is carefully cut, usually using a sharp tool like a knife or pruning shears.
b) The cut stem is then planted in the soil. Over time, the cut stem starts to develop roots from the lower end and leaves from the upper end.
c) The stem essentially transforms into a new plant.
d) Rose and sugarcane are generally propagated by this method.

2. Reproduction by Layering

a) Reproduction by layering is a method of vegetative propagation where a healthy branch of a plant is bent and partially buried in the soil.
b) Roots develop from the buried portion of the branch, and once a strong root system forms, the branch is separated from the parent plant.
c) The separated branch then grows into a new plant.
d) This method is used for plants such as grapevine, jasmine, lemon, cherry, and croton.

3. Reproduction by Grafting

a) Reproduction by grafting is a method of vegetative propagation where two different plant parts are joined together to create a new plant.
b) It involves taking a piece of one plant, called a scion, and attaching it to the stem of another plant, called the stock.
c) The scion and stock are carefully joined together so they can grow as one plant.
d) This method allows us to combine different qualities and characteristics from different plants. For example, we can take a good-tasting fruit tree and attach it to a strong and sturdy tree to make a new tree with both good taste and strength.
e) Grafting is a common method for propagating roses, grapevines, oranges and apples.