Reproduction in Plants PDF

## Reproduction in Plants ### Learning Outcomes After completion of the chapter, students will be able to: 1. understand asexual reproduction. 2. explain and identify different ways of vegetative propagation. 3. describe sexual reproduction in plants. 4. explain pollination and fertilization. 5....

## Reproduction in Plants ### Learning Outcomes After completion of the chapter, students will be able to: 1. understand asexual reproduction. 2. explain and identify different ways of vegetative propagation. 3. describe sexual reproduction in plants. 4. explain pollination and fertilization. 5. describe the formation of seeds and fruits. 6. discuss about the dispersal of seeds. One distinct feature of living things which makes them different from non-living things is their ability to reproduce. All living things eventually die, but the population does not perish with the death of the individuals. This statement implies that the living organisms continue to give birth to their own kinds. The production of new individuals of the same kind by the parents of the same species is known as reproduction. Every kind of organism has its own way of reproducing. There are two main types of reproduction: sexual and asexual. Almost all animals, and many plants, reproduce sexually. But some plants, a few animals and many simple organisms reproduce asexually. Some may even reproduce both ways. ### Asexual Reproduction The method of reproduction that does not involve the fusion of male and female gamete is known as asexual reproduction. The new plants obtained are identical to the parent plant. New plants are obtained without formation of seeds or spores. Asexual reproduction is also carried out by various methods which differ from plant to plant. They are: * Vegetative propagation * Budding * Fragmentation * Spore formation ### Vegetative Propagation In this type of asexual reproduction new plants are grown from leaf, stem, bud or root. There are vegetative part of plant so it is called vegetative propagation. ### Vegetative reproduction by stem A number of plants such as potato and ginger can give rise to new plants vegetatively from stem. ### Activity 8.1 - Objective: To study vegetative reproduction in potato tuber. Materials required: A fresh potato, soil. Procedure: * Take a fresh potato. Cut it into pieces such that each piece gets the portion of potato having an 'eye'. * Bury these pieces in the soil with some distance between them. Keep the soil moist. * After a week, loosen the soil and observe the potato pieces. Observation: You will observe that the 'eyes' of the potato pieces have started sprouting. The new roots and leaves coming out from these eyes are the new baby plants. ### Know The Fact! * Node is a point on the stem of a plant where a leaf is attached. * Buds are the growing points of a plant. * A tuber is the thickened underground stem of a plant which is swollen with stored food. When potato is cut into a number of pieces and each piece containing an 'eye' is planted into soil, each individual piece develops into a new plant. Each eye, in fact, is a bud. When potato sprouts the roots and leaves start coming out from these eyes or buds. As potato is an underground stem and is known as tuber this type of reproduction is vegetative propagation by stem. Ginger and turmeric which also grow under the soil as modified stems reproduce in similar way, when conditions are favourable. Vegetative reproduction through bulb is seen in case of onion and Gladiolus. A bulb is a very short stem which is swollen because of the food stored in it. In a particular season, the bulbs are put in soil where they multiply and form new bulbs. ### Vegetative reproduction by leaves In Bryophyllum, the leaf has buds at the edges or margins. Each bud gives rise to a small plant bearing leaves and roots. In due course of time, these new plants get detached from the mother plant, fall on the ground and form a new Bryophyllum plant. Another plant called Begonia also reproduces by vegetative propagation through its leaves. ### Vegetative reproduction by vegetative buds A vegetative bud is different from a flower bud and is present in the axil of leaves. An axil is the point of attachment of the leaf at the node. It consists of a short stem around which are found overlapping leaves. This bud develops into a new plant. ### Vegetative reproduction by root Plants like sweet potato, dahlia, tamarind, and Asparagus develop many large swollen fleshy roots. These fleshy roots contain food inside them. Each root is like bud and is capable to form a new plant. The plants such as cacti produce new plants when their parts get detached from the main plant body. Each detached part which falls on the ground can grow into a new plant. ### Artificial Methods of Vegetative Reproduction Some of the artificial methods of vegetative reproduction are discussed below: ### Layering In case of layering, lower branch of a plant is bent down and covered under a thin layer of moist soil by pushing the tip into the soft ground. After a few days, plantlets can be separated out and can be grown as a separate plant. This is known as layering. These plantlets can be separated out and can be grown as a separate plant. This is known as layering. ### Grafting A small branch of a plant is tied with the cut stem of a rooted plant of the same type. The joint is covered by a layer of wax or clay. After a few days, the two become united and develop into a new plant. The rooted plant with the root system under the soil is called as stock. The stem cutting of another desired plant is known as scion. The stem cells of the scion and the stock soon connect, with each other rapidly, as if they belong to the same plant. This is facilitated by the stock that supplies the desired nutrients to the scion. This method is used to grow mango, lemon, rose plants, etc. It is very useful method for plants which are difficult to grow from seeds or cuttings, and also gives desired varieties. ### Cutting This is a very common method to grow rose plants, sugar cane, etc. A small cutting of stem (a stem piece) is taken and placed in the moist soil. After a few days, this stem gives rise to roots and forms new plant. ### Activity 8.2 - Objective: To study vegetative reproduction by means of cuttings. Materials required: A piece of rose cutting, a pot with soil. Procedure: * Cut a branch of rose with a node. This piece of branch is 'cutting'. * Bury the cutting in the soil. The part having the node is kept above the ground. * Water the cutting every day and observe its growth after few days. * What change do you observe in its growth. Observation: After a few days, the end of cutting buried in the soil develops roots. The bud develops into a shoot. Money plant can also be grown by the cutting method of vegetative propagation. We can grow money plant by keeping the stem cutting in a jar of water. ### Advantages of vegetative reproduction * Some of the plants such as bananas which do not produce seeds at all multiply only by vegetative reproduction. * Vegetative reproduction takes less time for plants to grow and bear flowers and fruits as it does not involve germination of seeds. * In some cases where the seeds produced are not viable or fit and cannot form new plants, vegetative reproduction is used. ### Disadvantages of vegetative reproduction * The new plants formed through vegetative reproduction are exactly like the parent plants. If the plants with similar qualities as that of the parent are required, vegetative propagation is the best method. * Since vegetative reproduction produces an exact copy of the parent, some undesired qualities of the parent plant also pass on to the plants of new generation. * All plants are vulnerable to the same disease. * Germs can get passed from parent plant to offspring.