Reproduction in Plants PDF

# Reproduction in Plants ## Chapter 7 "The process of producing young ones from their parents is known as reproduction." ## Introduction - All living organisms reproduce. - Living organisms produce young ones of their kind. For example, a cat produces kittens which grow into adult cats. In plant...

# Reproduction in Plants ## Chapter 7 "The process of producing young ones from their parents is known as reproduction." ## Introduction - All living organisms reproduce. - Living organisms produce young ones of their kind. For example, a cat produces kittens which grow into adult cats. In plants too, seeds grow into young seedlings. The seedlings in due course of time develop into mature plants, as in a mango tree. - Reproduction is one of the most important properties of living organisms. It means creating new life, producing young ones of their own kind. ## Why living organisms need to reproduce? - All living organisms have a fixed life span. During their life span, the organisms perform various life functions including reproduction. - In an annual plant the life span is about one year, and in a perennial plant, it goes up to many years. - Then the organisms die leaving behind individuals of their own kind. Thus they ensure by reproducing during their life span. If they would not reproduce, then after their death, there would be no organisms left. - The species would thus perish. - Reproduction is, thus, the means of perpetuation of species. ### Modes of reproduction #### Flowers produce seeds - Seeds are formed by the fusion of a male gamete with a female gamete. - We sow these seeds and grow more plants of the same type. - This is the most common method of growing new plants. - This type of reproduction is called **sexual reproduction**. #### Can we grow new plants without seeds? - Yes, There are some plants which do grow without seeds. - These plants give rise to new plants from a part of stem, root or leaf. - These parts of the plant are called **vegetative parts**. - For example, a new plant of rose is produced by growing a cutting from one of its branches. - This type of reproduction, which takes place without seeds, is called **asexual reproduction**. ## Asexual reproduction in plants - **Budding:** Asexual mode of reproduction in which a small outgrowth (bud) appears on the body of the organism. Budding is commonly observed in yeast. - A bulb-like projection, called the bud, is formed on the body. - The nucleus of the body divides into two. Then, one of the two nuclei passes into the bud. - The bud detaches itself from the parent body. - It grows to full size and becomes a new individual. - **Fragmentation:** In some filamentous organisms such as Spirogyra (an algae), the filaments break up into two or more fragments. Each fragment or piece grows into a new individual - **Spore formation:** In non-flowering plants (the plants which do not produce seeds), like fungi (Mucor), bacteria, ferns or mosses, formation of spores is a common method of reproduction. - Spores are very small in size. - They have thick walls. - The thick walls help the spores to survive adverse conditions in the environment, like high temperature, scarcity of water and lack of food. - The spores give rise to new organisms under favourable conditions. - **Vegetative propagation:** This is an asexual method of reproduction in plants where vegetative parts namely the root, stem, leaf or buds give rise to new plants. No reproductive organs take part in this method of reproduction and therefore, no seeds are produced. - **Vegetative propagation by roots:** In sweet potato, dahlia or asparagus, the swollen roots are present. New plants arise from these swollen roots buried in the soil. - **Vegetative propagation by stems:** A number of plants like potato, ginger, turmeric do vegetative propagation by stems. - The potato which you eat is in fact an underground swollen stem (tuber) which contains stored food material. - If you observe a potato with a magnifying glass, you will find "scars". These scars are called 'eyes'. - The 'eyes' on the potato tuber sprout (germinate) and give rise to new plants. - **Vegetative propagation by leaves:** In Bryophyllum, plantlets develop from the margins of intact leaves. These plantlets on being detached, develop into independent plants. - **Advantages of vegetative reproduction** - It is an easier, rapid and less expensive method of propagation. Plants can be grown in much less time. - Seedless plants can be raised. - Plants produced by this method are identical copies of the parent plant and show no variations. - Plants like banana, sugarcane, sweet potato, rose and jasmine do not produce viable seeds. Such plants can be easily grown by this method. ## Artificial methods of vegetative propagation - Because of the advantages offered by vegetative propagation, humans have used this method for artificial multiplication of useful plants. - For this reason, such multiplication methods are called artificial methods of vegetative propagation. - Some of these methods are as follows: - **Cutting:** Artificial method of vegetative propagation in which short lengths of plant stem or root are used for growing new plants. - **Stem cutting:** Cuttings are short length of the plant which, when removed and placed in soil, with suitable conditions, develop roots and leaves and grow into independent plants. - **Root cuttings:** In certain plants like lemon, tamarind, etc. root cuttings when put in the damp soil give rise to roots and shoots and form new plants.