Multiplication in Plants PDF

Okay, here's the conversion of the provided text into a markdown format. I've focused on structuring the information clearly and accurately. # Chapter 10: Multiplication in Plants **You Will Learn About** * Multiplication in plants * Asexual reproduction in plants * Sexual reproduction in p...

Okay, here's the conversion of the provided text into a markdown format. I've focused on structuring the information clearly and accurately. # Chapter 10: Multiplication in Plants **You Will Learn About** * Multiplication in plants * Asexual reproduction in plants * Sexual reproduction in plants * Pollination * Germination of pollen and fertilization * Dispersal of seeds and fruits All living organisms have an instinct to live their own lives and also produce (or give birth to) new ones of their own kind. This instinct is helped by the process of multiplication, that is, the creation of new living organisms by the existing living organisms. This process is known as reproduction. This is true for both, the plants and animals. Each living organism has a definite lifespan. Before an organism dies it produces new living beings similar to itself. Thus, multiplication or reproduction can be defined as the ability of living organisms to produce new organisms of their own kind. Reproduction in organisms (plants and animals) not only increases their number but also saves the species from extinction. ## Multiplication in Plants Plants multiply or reproduce by different methods. These methods are grouped into two types: asexual reproduction and sexual reproduction. To understand the difference between **asexual** and **sexual reproduction**, let us first study in detail about flowers. ### Parts of a Flower A flowering plant has root, stem, leaves, and flowers. Root, stem, and leaves are the **vegetative parts** and flowers are the **reproductive parts** of a plant body. Many flowers eventually change into fruits. Fruits bear seeds. In most flowering plants, new plants come from the seeds. Seeds help in the multiplication of plants. They are produced as a result of the fusion of male and female reproductive cells or the **sex cells.** The reproductive cells or sex cells are called the **gametes**. Gametes are of two types: male gametes and female gametes. Male gametes come from the male reproductive part of a flower (anthers on the stamens) and the female gametes come from the female reproductive part of a flower (ovules in pistil or carpel). Male and female gametes fuse with one another forming a single cell called the **zygote or oospore**. The zygote cell divides repeatedly forming a seed, which on sowing gives rise to a new plant. The process of reproduction in which male and female gametes unite to form a zygote and that zygote rise to a seed is called **sexual reproduction**. ### Types of Flowers in Flowering Plants Flower is the reproductive part of a plant. It has four main parts or whorls (i) outermost green sepals (ii) colored non-green petals (ii) male reproductive part, the starnen and (iv) female reproductive part, the pistil or carpel. Sepals and petals are the vegetative or non-reproductive parts of a lower, stainen and pistil are the sexual or reproductive parts of a flower * **Complete or Bisexual Flowers:** A flower bearing all the four parts (sepals, petals, stamen and pistil), are called complete or bisexual flowers. Bisexual flowers are also called hermaphrodite flowers. Most plants bear bisexual flowers. Hibiscus, China rose and mustard are some examples of plants bearing bisexual flowers. * **(b) Incomplete or Unisexual Flowers:** Flowers bearing sepals and petals along with either the male reproductive parts (stamens) or female reproductive parts (pistil or carpel) are called incomplete or unisexual flowers. Cucurbits (gourd), papaya and corn (maize) are some plants that bear unisexual flowers. * **Neutral Flowers:** Neutral flowers are the flowers having sepals and highly decorative petals only. They lack reproductive parts. Plants with neutral flowers are cultivated for decoration purposes. The ray florets of sunflower and cultivated chrysanthemums are neuter or neutral flowers. ### Asexual Reproduction in Plants In asexual reproduction, plants are able to produce new plants without the formation of gametes, that is, the sex cells. In the process of asexual reproduction, only a single parent is involved. The common methods of asexual reproduction in plants are: * Vegetative propagation or vegetative reproduction * Fission * Budding * Fragmentation * Spore formation ### Vegetative Propagation or Vegetative Reproduction Vegetative propagation is the growing of new plants from the vegetative parts such as root, stem or leaf of a plant body. You have learnt earlier that a bud is the growing point on a plant body. On a plant, the bud present at the apex of the stem is called the **terminal bud** and that present in the axils of leaves are called the **axillary** or **lateral buds**. The buds may grow out into leafy branches. Such buds are called the vegetative buds. Some buds may grow into flowers. Such buds are called the floral or flowering buds. Axillary vegetative buds at times give rise to new plants. * Vegetative Propagation with the Help of Roots You might have seen the swollen roots of sweet potato and Dahlia plants. These roots store food and bear buds towards the joint where they are attached to the stem. On sowing these roots along with the buds, new plants come out of the buds. * Vegetative Propagation with the Help of Stems By aerial stem. New plants can be obtained from aerial stem bearing roots at the node. In grass, mint, strawberry and chrysanthemum, the stem grows along the soil. These sub-aerial stems are known as runners. The sub-aerial stem gives rise to roots and buds at each node that may grow out into new plants thus helping in multiplication of plants. * By underground stems Stem tuber in potato, rhizome in ginger or turmeric, corm in Colocasia, Gladiolus or Alocasia (arbi/kachalu), bulb in onion, and an 'eye' from sugarcane or potato plant bear buds on their food laden underground stem. These buds may grow into new plants under favourable conditions thus helping in vegetative propagation. #### Activity 2 Aim: To show vegetative propagation in potato. Take a potato tuber (not a fresh one) with dry skin. Examine it. You will find potato tuber bearing prominent eyes on it. Each eye is a bud present in the axil of a scale leaf. Cut a piece from the potato with an eye on it and place it in the soil at a warm place for a few days. In a few days, you will find the bud growing out of tuber into a new plant. If a potato tuber (whole) is planted in soil, all the buds on it may grow into a number of new plants. Similarly, rhizome, corm and an onion bulb also help in vegetative propagation. #### Induced or Artificial Methods of Vegetative Propagation Humans have developed certain artificial methods of propagating plants. These methods are specially used for multiplying flowering and fruit plants. These methods are more useful in obtaining new plants bearing the same characters as that of the original plants. These artificial methods are: **Stem cuttings** Rose, Bougainvillea, cactus and many hedge plants are multiplied with the help of stem cuttings. In this method, the stem cutting bearing a bud, from these plants, is planted in a moist soil. After some time, a new plant grows out from this stem cutting. #### Activity 3 Aim: To obtain a new plant from a piece of Opuntia blade. Get a piece of fleshy blade from a cactus (Opuntia) plant (may be without roots) and fix it in the soil with its cut end. Piece from the cactus will grow into a new plant. #### Activity 4 Aim: To obtain a new plant from stem cutting of rose plant. A fresh piece is cut from a mature stem of rose plant bearing a bud. The piece of branch is given a cut at its lower end with a sharp knife. The cut end is dipped in animal urine from a cattle or a dilute solution of urea and is pushed a little into the manure rich moist soil. In a few days, the cutting develops roots on its underground part and the aerial part along the bud starts growing to form a new plant. Note: Urine or urea stimulates the growth of roots from the cut stem. ### Spore Formation It is a common method of asexual reproduction in many of the non-flowering plants like algae, fungi (including moulds), mosses and ferns. Spores are formed in sporangia (singular: sporangium), the special structures which are formed on these plants. Spores produced are minute, unicellular and large in numbers. On maturity, spores come out of sporangia and float freely in air for dispersal all over. On falling upon a suitable base (food and moisture) each spore grows into a new plant. #### Activity 5 Aim: To prepare a culture of mould (fungus) on a piece of moist bread. Procedure: Take a slice of fresh or moist (not dry) bread and place it in a closed box at a warm place. Open the box after a few days. You will find moulds growing on the bread. The moulds may be bearing projecting stalked globular sporangia filled with black, yellow or blue spores, depending upon the species. Some common moulds are Mucor, Rhizopus, Aspergillus, Penicillium and others. Spores from various moulds are ever present in air and they easily grow on stale bread or any other moist food exposed to air. Precaution: While opening the box with stale bread on which mould has been cultured, take care that the spores may not come on your skin or face. The spores are generally large in numbers and loosely placed, and so may get into your lungs through the mouth or nasal cavity and may cause fungal disease of throat and lungs. #### Test your learning outcome 1. List the methods of vegetative propagation of plants. 2. Mention the asexual method of multiplication in the following: a. bacteria b. yeast c. Rhizopus d. Spirogyra e. potato tuber f. Bryophyllum g. jasmine h. rose i. mango 3. What is induced vegetative propagation? Explain giving an example. 4. Name the following: a. Multiplication method in which only one parent is involved. b. Reproductive method that needs two parents. c. Process in which one cell divides into two and two into four. d. Process of body fragment growing into a new plant. 5. List the advantages of vegetative propagation of plants. ### Advantages of Asexual Reproduction / Vegetative Propagation 1. This is a rapid method of multiplication of plants. It also saves on the cost of seed. 2. Even seedless varieties of plants (like roses, bananas, grapes, guavas and others) can be cultivated vegetatively. 3. New plants obtained through asexual reproduction are exactly similar to the parent plant. 4. Plants grown asexually need less attention in early stages since they are not destroyed by birds and other animals (seeds sown in many cases are eaten away by birds and other animals). ### Sexual Reproduction in Plants Most plants reproduce sexually. Sexual reproduction helps a plant in overcoming unfavourable weather and the season. Flowers bear the sexorgans. Seeds are the product of sexual reproduction in flowering plants. Seeds are produced towards the approach of unfavourable season. The seeds survive through unfavourable conditions and germinate to grow under favourable conditions (may be in the next season) to give rise to new plants. Seeds in a plant are produced in large numbers and each seed is capable of growing into a new piant. Thus, seeds help in the multiplication of plants. Sexual reproduction involves the fusion of male and female gametes. Gametes are produced in separate male and female reproductive organs. The reproductive organs are parts of a flower. Both, male and female sex organs (stamen bearing anthers and pistil bearing ovules) may be present as a part of the same flower on the same plant or in separate flowers on separate male and female plants. ### Parts of a Flower Each flower has sepals as its outermost part. Sepals are generally green and they protect the flower bud. The next part of a flower are the petals which are non-green (white or may be of any colour other than green). Petals are generally soft and fragrant and are the attractive part of a flower. Sepals and petals are the vegetative parts of a flower. Next are the stamens bearing stalked bilobed anthers filled with pollen grains. Centrally placed on the stalk of the flower is the flask shaped pistil or carpel bearing ovules, each ovule bearing a female gamete. ### Stamens Stamen is the male reproductive organ of a flower. Each stamen is a stalked structure bearing bilobed globular anther at its free end. The bilobed anther possess four chambers. Each chamber on the anther is filled with granular pollen grains. Each pollen grain bears two male sex cells or the gametes within it. Externally, a pollen grain may have smooth or spiny hard protective wall. ### Pistil or Carpel It is the female reproductive organ of a flower. Pistil is a flask shaped structure. The globular part of pistil is the ovary, the neck is the style and upper broad tip of the style is the sticky stigma. The ovary includes one or many globular ovules. Each ovule bears an eight celled egg apparatus. Of the eight cells one is the female sex cell called the female gamete or egg. Egg apparatus in an ovule is formed from a mother cell in a young ovule. The mother cell along with its nucleus divides by binary fission into eight nuclei. Of the eight nuclei, three remain at one end of the egg apparatus, the other three moves to the other end which is towards the mouth of the egg apparatus and two nuclei reach the centre of the egg apparatus. One of the three nuclei which move towards the mouth of the ovule functions as egg cell #### Activity 6 Aim: To study the structure of a pistil and the presence of ovules in it. Collect a fresh flower from a plant. Remove the sepals, petals and stamens from it. Study the shape of the pistil and its three parts: ovary, style and stigma. To observe the ovules, cut open the ovary. Globular ovules will be seen inside the chambers in the ovary. For study, better collect a young green lady's finger fruit. Lady's finger comes from an ovary. Give a transverse cut to the fruit (ovary) and study the shape of the ovules and the attachment of the ovules to the ovary wall. In the process of reproduction in flowering plants the pollens from anthers are transferred to the stigma on the pistil. This transferring of pollens from anthers to the stigma on pistil is termed as pollination. Stigma on a pistil is sticky. As soon as the pollens fall on the stigma they get attached to it. ### Pollination Transfer of pollens from a mature anther to the stigma of a pistil is called pollination. Pollination is of two types: self-pollination and cross-pollination. 1. **Self-pollination** 2. **Cross-pollination** #### Pollination Test your learning outcome 1. Draw and label the different parts of a flower. 2. Which parts of a flower heip in sexual reproduction? 3. In which part of a flower do we find the pollen grains? 4. Which part of a flower contains ovules? 5. Where should we search for male gametes in a flower? 6. What is the location of egg cell or female gamete in a flower? #### Self pollination Is the pollination that takes place within the same flower or different flowers on the same plant. An interesting example of self pollination is the lily flower in which on maturity, movement of the stamen bends over the stigma within the same flower to shed the pollens. #### Cross-pollination is the pollination that takes place between the flowers on different plants of the same kind (species). Pollens being small and light in weight are carried by certain agents of pollination. Wind (air), water, insects, birds and other animals are some agents of pollination. Agents of pollination are also called pollinators. Among unisexual flowers pollination is naturally cross-pollination. **Agents of Cross-pollination (the Pollinators)** **Pollination by Wind (Air)** Wind is the natural and common agency of pollination. Blowing wind carries pollens from the anthers of one flower to the stigma on the pistil of another flower. Some of the features adaptations of wind pollinated flowers are: 1. Wind pollinated flowers are not bright and coloured and they do not produce nectar. 2. Pollens are produced in large numbers to overcome the loss in transit. 3. Pollens are light in weight so that they can easily float in air to be carried to distant places. 4. In some plants (like pines) pollens are winged. Stamens hang in air to release the pollens even with the slightest blowing of air. Stigma on the pistil is sticky and it hangs out of the flower. 5. Maize plant is specially adapted to wind pollination. It bears unisexual flowers. A bunch of male flowers are placed terminally at the top of the plant to release pollens as dust particles. Female flowers are placed below in cobs. Long and sticky thread-like styles hang out of the cobs placed below in the axils of the leaves. Pollens from male gamete float in air to reach the hanging styles and stigma from female flowers. Grass plants like common grasses, sugarcane, wheat, paddy, barley, corn (maize) are some plants in which pollination takes place by wind. #### Pollination by Water Flowers of aquatic (water) plants are pollinated by water. Pollen grains coming out of anthers rise and float on water and are carried to the stigma with the water currents. Pollination by water takes place in plants like Hydrilla, Vallisneria, Zostera, water lily and other water plants. ### Pollination by Insects, Birds and Other Animals Flowers which are colourful, fragrant and filled with nectar are pollinated by insects, birds and other animals, including human beings. These flowers show special adaptations for cross pollination by animals. These adaptations are: * Flowers are colourful and scented (fragrant) to attract insects and animals, including human beings. * Most flowers secrete nectar, a sweet liquid which remains at the base of the petals towards stamens to attract insects. * In many cases, flowers are massed together into a dense inflorescence (tuft of flowers) which helps immediate pollination of many flowers with a single visit of an insect. For example: sunflower. * Animals while rubbing their body against the flowers pollinate them. * Birds visit flowers in search of food (insects) and to suck nectar. During their visit they carry pollens from one flower to the stigma of the other flowers, thus helping in pollination. An interesting example of pollination by birds is the pollination by sunbird or the humming bird. Both the birds have a long beak and a small body Sunbird visits the tubular flowers to pick and eat insects and suck nectar from them and thus helping in pollination. Almost every flower is visited by one or the other insect. Typical examples of cross pollination by insects are as follows: 1. Flower on Salvia plant is so designed by nature that when an insect enters it, the anthers stick to the body of the insect. When this insect visits another flower it sheds the pollens on the stigma of that flower, thus helping in pollination. 2. Flowers of tuberose (Raat-ki-rani or Rainlgandha) are white in colour. They reflect moonlight and start emitting a strong fragrance with the sunset and continue with it during the night. Insects are attracted by the bright flowers, their fragrance and nectar. They visit the tubular flowers and help in pollination. ### Germination of Pollens and Fertilization A pollen on reaching the stigma of the pistil belonging to a flower from a similar plant species germinates to give out a pollen tube. The pollen tube grows through the style of the pistil to reach the ovary where ovules are present. The two male sex cells (male gametes) from the pollen move into the pollen tube along its tip to reach the ovary and the ovule. On reaching the ovule, the pollen tube bursts open and pushes the male gametes into the egg apparatus. One of the male gamete unites with the female sex cell (female gamete or egg) and the two fuse together. The fusion of the egg cell (female gamete) with the male gamete is called fertilization. Many pollens may fall upon a stigma and germinate to form as many pollen tubes reaching the ovules but only one male gamete fuses with one egg cell in an ovule. ### Product of Fertilization, the Embryo The product of fertilization is called the zygote or oospore. Zygote cell divides and redivides to form the baby plant or embryo. Except ovary, all the other parts such as sepals, petals, stamens, style fall off. The walls of the ovules grow into layers and form seeds. The baby plant remains attached to the food laden cotyledons which come from the body of the ovule. This way an ovule on fertilization develops into a seed. Hence a seed consists of baby plant which grows out into a new plant when the seed is sown. While the ovule develops into a seed, the ovary matures into a fruit. ### Importance of Fertilization and Formation of Seed Union of two gametes brings about the combination of the characters from male gamete and female gamete coming from two different varieties of the same species. Thus, the seed formed bears mixed characters of the two parent - #### Good to Know One of the two male gametes in a pollen tube fuses with the egg cell resulting in fertilization. The second male gamete also enters the ovule and pushes further into the ovule to reach the centrally placed two polar nuclei and the three nuclei fuse together. This newly formed nucleus, formed by the fusion of three nuclei, divides and redivides forming the endosperm part of the seed. Endosperm develops in a few seeds to store food in place of cotyledons. Examples in which endosperm is formed in the seed are maize, rice, wheat and other grains and castor seed. In flowering plants, fusion of two male gametes takes place at two places in the same ovule; one between the egg cell and the gamete and the other between the pair of polar nuclei. This is called double fertilization. the fruit tract in the body of the birds. The seeds remain undigested, These seeds are dispersed vid the droppings by the birds at different and distant places, You might have seen Peepal plants growing along the crevices on walls, treetops of tall buildings and along the drains. The seeds from fruit on Peepal tree are dispersed by birds, #### Test your learning outcome 1. What is fertilization? 2. In what way, male gametes reach the ovule in an ovary? 3. What is the product of fertilization? 4. Which part of a flower after fertilization develops into (a) seed, (b) fruit? 5. List the functions of (a) seed (b) fruit. 6. List the different agents that help in dispersal of fruits and seeds. 7. Is self-pollination possible in maize. Why or why not? ## In Brief * All living organisms including plants multiply to help the survival of their race. * Reproduction is the process of multiplication. * In plants, there are two modes of multiplication: asexual and sexual. * Asexual multiplication takes place by a single parent and by means of its vegetative cells, * Sexual reproduction involves gametes from two parents. * Flowers are the reproductive parts of a plant. * Flowers bear stamens which hold bilobed anthers filled with pollens. * Pollen bears two male gametes. * Pistil or carpel on a flower bears ovules. * Ovule bears the egg cell or female gamete. * Male and female gametes fuse (unite) to form zygote or oospore. * The union of gametes is called fertilization. * On fertilization, ovule develops into a seed and pistil into a fruit. * Seeds germinate and give rise to new plants helping in multiplication of plants. ## Terms At A Glance * **Asexual reproduction:** A single parent giving rise to a new plant * **Bisexual organism:** Organism bearing both the male and female gametes Binary fission: One cell dividing into two, two into four and so on * **Budding:** Multiplying by means of the formation of bud as in yeast * **Fertilization:** Fusion of a male gamete with female gamete forming zygote or oospore * **Pollination:** Transfer of pollens from anther to the stigma on the pistil Let me know if you need any adjustments or further refinements!