Ch11 Reproduction in Plants PDF

Unit 3 | The World of the Living REPRODUCTION IN PLANTS CHAPTERPREVIEW Asexualrreproduction in plants SexualIreproduction in plants youwilllearn learn about the difference hetween asexual and sexual modes of reproducti...

Unit 3 | The World of the Living REPRODUCTION IN PLANTS CHAPTERPREVIEW Asexualrreproduction in plants SexualIreproduction in plants youwilllearn learn about the difference hetween asexual and sexual modes of reproduction Learn about types of asexual reproduction in plants Understand how sexual reproduction takes place inplants Itis important to learn Plants are very important for life on the Earth. Reproduction in plants Ihvolves parts of the plant such as 21st roots, stems and flowers. Animals WARM-UP Skills Century Thought provoking Such as bees and butterflies also help All animals produce young ones similar to themselves. in reproduction of plants. Reproduction is necessary for the continuation of life on Earth. Inerefore, it is important to learn bOut asexual and sexual modes of How do plants reproduce? ls reproduction in plants similar eproduction in plants. toor different from that of animals? 137  Before we lgarn about Reproduction is afundamental Icharacteristic of allliving things. reproduction. reproduction in plants, let us recall some plant parts that help in Most plants have roots, stems and leaves. These are called vegetativ parts of aplant)After plants the most of them bear flowers. Flowers perform have grown to a certain stage, m function of Teproduction in plants and are known as the reproductive parts of aplant) Different plants have different methods of reproduction. However, these different be grouped under two categories--asexual reproduction and sexual reproduction. methods Can What is asexual reproduction in plants? The method of reproduction in which the offspringg are produced from the vegetative part of the parentplant is known as asexual reproduction. In asexual reproduction, asingle parent is involved and offspring are identical to the parent. In asexual reproduction, new plants can be grown from the parent plant without seeds. Asexual reproduction takes places in a few different ways and can take place by natural as wal as artificial methods. What are the types of natural methods of asexual methods in plants? In nature, there are several ways in which asexual reproduction takes place. Some natural methods of asexual reproduction are budding, spore formation, fragmentation and vegetative propagation. Developing bud Daughtbudser Budding: Budding occurs in unicellular organisms such as yeast (Fig. 1l1.1). In Mother cell budding, a small part of the body of the parent (mother cell) grows out as a bulb-like projection called 'bud. The nucleus of the mother cell divides into two and one part moves to the growing bud. This bud then increases in size and separates forming another yeast cell. Sometimes, Fig. 11.1 Budding in yeast the buds do not detach fromn the mother cell and instead form chains of buds. 21st Test It Yourself!Century Observation Skills To observe budding in yeast. 1. Take a small spoon of yeast powder (easily available in the market) and put it in a transparent glass. 2. Add a small spoon of sugar and ½ a cup of slightly warm water. 3. Mix it all together. Cover the glass and leave it for some time in awarm place. The liquid inside the glass froths and rises, and sometimes even spills over! The liquid 'grows' because of the reproduction of yeast. Ifa drop of this liquid is placed under a microscope, budding in yeast cells can be cleary seen. 138  rmaton, In plants such as moss, ferns and brend moulds, speclal sdevelopasexually on the parent body. These microscopic reproduct structures ive are caled gll.2).They are covered by aprotective wall, When the spores mature, they are he plant body. Whenthe spores reach asuitable environment, they developinto yenplant tonditions are untavourable for growth, spores remain in the protective wal conditions appear. Clusters of spores Custgrsofspores Spores b. Fern c. Bread mould a.Moss Fig. 11.2 Sporeformation in moss, fern and bread mould fragmentation:This is anmethod of asexual reproduction in plantssuchas flamentous algae. These algaeare made Growth seen strandscalled filaments. These filaments break up Fragment1 long upof pieces andeach piece or fragment grows into intooone or more anewplant(Fig. 11.3). The breaking " up of the parent plant Growth eachnof which grows to form anew two or more pieces, Fragment2 into fragmentation. plant,iscalled formation of new Vegetative propagation: Itinvolves the plant (Fig. 11.4) such plantlets from the vegetative parts of a Growth Fragment 3 as root, stem or leaf. The part gets detached from the parent plant. Fragmentation in a body and grows into an independent Fig. 11.3 filamentous alga (Spirogyra) place the roots of Vegetative propagation of roots: If we conditions, they some plants under the soil, given the right plants a. roots of grow into anew plant. Examples are (IVID turnips. such as Dahlia, carrots, sweet potatoes and of some Vegetative propagation of stems: Stems are stems plants can grow into new plants. Tubers that have buds known as 'eyes. These buds when planted can give rise to a new plant. For example, b tubers of potatoes. Some stems called bulbs are bulbs tnick, short and grow underground. Thesebulbs can give rise to new plants. For example, ot onion and garlic. Rhizomes of ginger and umeric as well as corms of Colocasia are stems that can grow and form new plants. Runners Fig. 11.4 Vegetative propagation in are horizontal stems that emerge from the main (a) potato, (b) garlic and () ginger. 139  stem and grow along the have nodes from ground. Runners which buds grow that in turn growinto newplants. For example, runners of strawberry and grass. Vegetasative such propagation of leaves: Leaves of certain plants theleaf margin Bryophyllu m (Fig 11.5) form buds on whenthey that develop roots. These leaf buds or plantlets, Fig. 11.5 Vegetativs fall on the soil, give rise to propagation in Bryophylurn new plants. What arethe types i reproduction in of artificial methods of asexual plants? When we use the parts for propagatingcrops or vegetative ornamental plants, it is termed as artificial vegetative propagation. Some artificialImethods of asexual reproduction are cutting, layering and grafting. Cutting: Many plants such as rose, Bougainvil ea, Croton, Coleus, money plant, and sugar cane are grown throughtheir Fig. 11.6 stem cuttings (Fig. 11.6). Cuttingssof plants such as money plant Cuttingin arose can even be grown in wate. Layering: In this method, alower branch of a plant is bent down and covered with moist soil leaving the growing tip above the sol (Fig. 11.7). Aring of barkis removed from the stem before it is bent down. In a few weeks' timewhen enough roots have on the underground portion, it is cut off from the developed parent and grown separately as an independent plant. Examples: plant jasmine, Fig. 11.7 strawberry, grapevine and Bougainvillea. Layering method Grafting: Grafting is atechnique of attaching asmall branch to a rooted plant (Fig. l1.8). The rooted stock and the branch attached to the stock plant is known as the Scion is known as the scion or graft. This scion or graft is the stem desired plant. Usually, the grafted end of stockcutting well with each other and are and or rubber-band until their bound firmly with adhesive tape from the scion tissues unite. The scion becomes a permanent part of the stock over time. The grafted branch grows with the from which the branch characteristics fit Stock of the plant O Look It Up! (7E Explore 1 Fig. 11.8 Grafting was taken, the stock plant grows with its own while the rest of Search online for answers and in class. discuss Grafting has been found extremelycharacteristics. useful in 1. What is propagating improved and fruits such as rose, varieties of various flowers What micropropagation is it used for? in plants banana and apple. Bougainvillea, Citrus, mango, 2. Why is grafting of plants done? HOW is it useful in Indian 3. Who is Kaleem Ullah agriculture? he known as the Khan? Why S Mango  advant the ages andanddisadvantages of asexual Ireproductionin plants? the hotare Ddersand S hantges, advantages disadvantages of asexual Ireproduction inplants. TE/Esternd quicker, easier isa and less pmultijplying This plants expensive methodof Real-world Connect! areidentical Plants orociuced by vegetative ofispring Itothe parent. The propagation take less time rarieties thus be can desired preserved genetically for use. to grow, and bear flowers Varietiesofornamental plants and fruit trees can be and fruits earlier than those multipledeasily: produced from seeds. pisadvantages: Innaturalasexualreproduction, there could be overcrowding and competition forspace the ofspring are separatedd unless Newvarieties artificial y. cannot be produced by natural asexual INT reproduction. Diseasestypicalof the species are rapidly transmitted and can be ddetrimentalto a crop. Section Review 1 7E Evaluate Todrawa contrast between different modes of asexualreproduction. researchertook samples from afresh dough of bread on slide AandI from stale bread with mould A B. qrowth onslide She observed the growth of organisms (on both slides under the slides microscope. Aand B? eresearcher on Whattypeeof asexual reproduction might have been observed by the Tick the corect option. 1 A-Budding, B-Fragmentation 2. A-Spore formation, B-Budding 3. A-Budding, BSpore formation 4. A-Fragmentation, BSpore formation What is sexual reproduction in plants? The method of reproduction inwhich the oflspring are produced from the reproductive parts of reproduction involves the fusion Sexual the parent plant(s) is known as sexual reproduction. separate male and female reproductive of male and female gametes. Gametes are produced in sexual reproduction is carried out aplant, organs. Since flowers are the reproductive parts ofparts. only by flowering plants. Aflower has four main " Sepals-the outer green part of aflower " Petals--the colourful part ofmost flowers " Stamenthe male reproductive part of aflower ' Pistil-the female reproductive part of aflower Hiowever, all lowers do not have all four parts. What are tthereproductive parts of aflower? reproductive parts (Fig. 11.9) of aflower. Flowers which contain either Stamen and pistil are the the maleand female unisexual flowers the pistil or stamens are called unisexual flowers. Both Corn, papaya and cucumber produce plants. may be present in the same plant or in different 141  wers. Mustard called bisexualflo rOse and Flowers which contain both stamens and pistilsare petunia have bisexual flowers. Language Check - IPentdeagrgaogyted Stamen: Astamen is the male reproductive part oa filament Findout what'stigma' Engie la'anguage. nd'style' flower. The stamen is made up oftwo parts: meanin the English and anther. The upper part is known as the anther. Make a sentence each It produces and stores pollen grains. Pollen grains words, with the new using the contain male gametes(male reproductivecells). meanings. Stigma Pistil: Apistil is the female reproductive part of a flower. It is generally found in Pistil, Style the centre of a flower. Apistil is made up of three parts: stigma, style and ovary. The stigma is the area where pollen grains are Filament Ant Ovule Stamen received during sexual reproduction. The style is the long stalk that connects the stigma to the ovary. The ovary Pollen Ovary produces one or more ovules which contain the female gametes (egg cells). Fig. 11.9 Reproductive parts of aflower An important step in sexual reproduction in plants is pollination. 21st Test It Yourself! Century Skills, Observation, Analysis To study the reproductive parts of a flower. (7E) Extend 1. Pluck a slightly wilted flower from a plant. Ensure that the flower Do You Know? is reasonably large. The fruitsS we eat are matured ovaries that 2. Carefully examine the stamen(s). Note the number of stamens on surround the seeds the flower. Observe an anther using a hand lens and draw what inside. Fruits such yousee. as mango are fleshy, 3. Carefully slice the pistil lengthwise and observe the ovary using a while fruits such as hand lens. Notice the small ovules within it. Draw what you see. almonds are hard. Share in class the structure of the stamen and the pistil you observed. What is pollination? The transfer ofpollen grains from the anther to the stigma of a is called pollination. Agents such as wind, water or flower insects help to transfer pollen grains from one flower to another. Pollen grains that are light are carried by wind, while pollen float in water to reach different flowers. grains of aquatic plants and butterflies are agents of Insects such as honeybees polination. As a bee pollen sticks to its body. When the bee flies to visits a flower. another flower, the pollen from its body getstransferredi to the other 42 flower (Fig. 11.10). Fig. 11.10 Polination by bee phnation, canbe eof two types: wfpollinaton:is when polen of a Peaplantsshowself-pollination.flower falls on its own or aflower of the same asspollnation: stigma is whenpollen from one falls on of a planto ofthe same type. Maize plantsflower the stigma of anotherflower Mterent show isthe processs of fertilisation. ifer pollination,an important step in seed formation cross-pollination. hatis ferilisation? pollen orain lands on thestigma, it the pollen thetube Aher 1his produces atube which is calledovary. grows down from the stigma through The male the style and into the gproductivecells in pollen grains travel through the pollen tube and i reachthe ovule andfuse ube egg in the ovule. This joining of cell the pith caleajertilisation the male reproductive celland the egg cell in a (Fig. 11.11). oeris Pollen grain Pollination- Stigma The ovary becomes a fruit. Sstyle Pollen tube Fertilisation Eg9 (ANM) Ovay Qvule Fertilised egg The ovary gets bigger and bigger. Fig. 11.11 Polination and fertlisation in aflower the seeds develop, the ovary The fertilised ovule or zygote in the ovary develops into aseed. As seeds until they are ready to ots bigger andchanges to become afruit. The fruit protects the germinating into bereleased. The fertilised ovules develop into seeds which are capable of dispersed from the parent plant and sedlings and new plants. Once seeds are formed, they get conditions. then germinate under favourable What is seed dispersal? ifthe seeds just fall to the ground under KPlants make seeds that can grow into new plants, but nutrients from the soil. Plants have sun, water or the parent plant, they might not get enough developed methods to scatter their seeds) spreading or scattering of seeds away from the parent plant is called seed dispersal. Dispersal Ihe by the bursting or explosion of the fruit. can be done by wind, water, animals or sometimes by wind are smaller seeds that Dispersal by wind: Seeds which are often dispersedcones) fir or hair-like or feathery bristles have wings(such as sycamore, maple, pine and They are light and get carried by (dandelions (Fig. 11.12a), milkweed and cottonwood trees). Wind to faraway places. bodies often rely on Dispersal by water: Plants which growin or around water many kilometres till water to transport ocean for it reaches land cifseeds.Coconut is fbrous and can float in the 143  (Fig. 11.12b). Water lily and lotusflowers(Fig. 1.12c) make a fruit that floats in water 10T avwhi andanchortothe floor of the pond. and then drops downtothe roots a. bottomtoDgrow C b coconut; (c) Lotus; fruit with seeds Fig. 11.12 (a) Hairy seeds of dandelion;(b) Fibrous (Xanthium) and Dispersal by animals: Some species of plantsuch as cocklebur or spines (Fig. 11.13a) on their fruits to attachthemselvesto the fur of mammals or burdock useofhogk or even the clothes of humans! The seeds of many plants are also dispersed featherthsroughbirt after passing the that have eaten them. digestive system of animals such as birds and monkeys Dispersal by explosion: Plants such as peas and some types of beans have pods that explode (Fig. 11.13b) when ripe. The forceful ejection sends the seeds flying as tar away as possible original plant. This method of seed dispersal is seen in plants such as castor, balsam, from the okra and jewelweed. lady's finger o b. Science Fact-7E Extend Like animals, plants also pass on their traits to their young ones. Some traits of plants are the size of the adult plants, the shape of the leaves,the colour of the Apea plant Before After explosion explosion flowers, the flavour of fruits Fig. 11.13 (a) Spines in Xanthium seeds; (b) and the presence of seeds. Explosion in pea plant Section Review 2 -(7E Evaluate I To observe how different types of plants grow new ones in order to 1 asexualand sexual modes of reproduction. differentiate between 1. Two students Aand B were rose plant and buried it into asked the to grow different plants. soil, Student Aused the stem of a After a fewweeks, the rose plant while Student Bplanted the grew and a cucumber plant seed of a cucumber plant. reproduction took place in the plants chosen by Student Aandgerminated. What mode of option. Student B? Tick the correct (a) Student A Sexual reproduction; Student B Sexual (b) Student A Sexual reproduction; Student reproduction (cStudent A-Asexual reproduction; StudentB-Asexual B- reproduction (d) Student Sexual reproduction A-Asexual reproduction; Student BAsexual ptioue sdea that any one of the the category,in pother connection with theircategories features. of cods night disperse betterthart teachertol etudents that the seeddispersal in mapleseed howeve, A treesdispersal in the takes place by Xonthiom plant takes air What features ofthese by animals plaeeplants make theit mode of seed dispersal different? Tick the correct option )Aanthim:wingedseeds; Maple: spiny seeds with hooks (6)Kanthium:spongy seeds; Maple: wingedseeds dHanthim:winged seeds;Maple: explosion ofseeds (d)Xanthium:spiny seeds with hooks; Maple: wingedseeds Experiential fLearning 21st Century Environmental literacy Skills Goal:Tofind out Some unusual methods of plant reproduction. reproductioninthe Whatto do: Conduct an internet search to find someinteresting information on grivenplants. Some interesting wmys in vohich thera plants roprduca 4 Gint Amazon wnter y