eee siamo — Study of Adaptations of Flowers for Pollination A o = 2 a F’ 6 o INTRODUCTION 4, The process of transfer of pollen grains from anther to the stigma of either the same flower or another flower of the same species is called pollination. 2, Pollen grains are immobile, hence require external agencies to reach to the stigma. ‘The external agencies involved in pollination may be abiotic (e.g., wind, water) or biotic (eg, insects, birds, bats, snails, birds). EXPERIMENT 1.1 ) AIM: To study the flowers adapted to pollination by different agencies (wind, insect and birds). REQUIREMENTS Fresh flowers of maize or any other cereal/grass, Salvia/Ocimum and Brassica (mustard) forceps, hand lens, slide, needle etc. PROCEDURE K Place the given flower on a slide and observe it with the help of hand lens. Note down the adaptations of the flowers meant for pollination by the external agencies. Maize Flowers (Anemophilous or Wind Pollinated Flowers) ‘The flowers of maize show following adaptations for pollination by wind. 1. ‘Themaize plant is monoecious and bears unisexual flowers. The male flowers are born in terminal inflorescence while the female flowers are born in axillary inflorescence. 2. Flowers are small and inconscipicous. 3. The fowers are colourless, odourless and nectarless. 4 Flowers are produced above the foliage or placed in hanging position. 5. Both the stigmas and anthers are exerted (.e., hang outside the perianth). © Anthers are versatile, and pollen grains are light, small and dusty. The pollen grains are produced in very large numbers.—_ 40 Comprehensive Laboratory Manual in Biology yi 8. Stigma is hairy, feathery or branched to catch wind born pollen grains. Male flowers . Pollen grains Versatile anther Elongated 5! Feathery ‘styles stigma Pollen grains of another plant ao Stigmas Fig. 1.1. Anemophily in maize. Fig. 1.2. Feathery stigmas and versatile anthers in a flower of grass. Salvia Flowers (Entomophilous or Insect Pollinated Flowers) ‘The flowers of Saliva show following adaptations for pollination by insects. 1. The flowers are showy or brightly coloured for attracting pollinating insects. 2. The flowers are born in verticellaster inflorescence to become conspicuous. 3. Flowers secrete nectar to feed visiting insects. Nectar glands are placed in such a position that an insect must touch both the anthers and stigmas. 4, The flowers have landing platform for the insects. 5. The flowers are protandrons with bilipped corolla and have turn pipe or lever mechanism. Each stamen has long connective which bears a fertile anther lobe at the upper end and sterile plate like anther lobe at the lower end. The two sterile anther plates block the path of insect: As the insect moves inward a young flower in search of nectar, its head pushes, the anther plates and forces the fertile anther lobes to strike against its back. In older flowers the style brings the stigma in such a position that it brushes against the bac of insect and collect pollen grains brought by the insect from a young flower. _: |i, a Experiment for Spotting a Closed stigma Sterile A anther lobe Fig. 1.3. Pollination in Salvia. A. Flower with mature anthers, enclosed stigma and short style. B. Shedding of pollen grains on the back of entering insect. C. Flower with mature stigma and withering anthers. D. Stigma receiving pollen grains from the back of entering insect. Bignonia/Callistemon (Bottle brush) Flowers (Ornithophilous or Bird Pollinated Flowers) ‘The flowers of Bignonia show following adaptations for pollination by birds. 1. The flowers are usually brightly coloured-red, orange, yellow or blue. 2. The floral parts are commonly leathery. Humming bird Fig. 1.4. Pollination in Bignonia. Humming bird collecting nectar from Bignonia flower and thus pollinating it.Study of Pollen Germination INTRODUCTION 1. Pollen grain or microspore is the first cell of male gametophyte. 2. The development of male gametophyte is precocious, i.., it begins inside the micro- sporangium or pollen sac. 3. The pollen grain is uninucleate in the beginning but at the time of liberation it becomes 2 celled—a small generative cell and a large tube or vegetative cell. 4. On the stigma, the pollen grain absorbs water and nutrients from the stigmatic secretion through its germ pores. 5. The tube cell gives rise to a pollen tube. The generative cell also descends into the pollen tube and divides into two male gametes. (EXPERIMENT 1.1 | AIM: To prepare temporary mount to observe pollen germination. REQUIREMENTS Fresh seasonal flowers, slide, coverslip, microscope, sucrose, boric acid, magnesium sulphate, Potassium nitrate, beakers etc. PROCEDURE Prepare a nutrient solution by dissolving 10 g sucrose, 10 g boric acid, 30 mg magnesium sulphate and 20 mg potassium nitrate in 100 ml of water. Take a few drops of this solution on a clean slide, and dust a few pollen grains from the stamen of a mature flower on it. ae the slidein the microscope after 5 minutes and then observe it regularly for about half an hour. OBSERVATION In nutrient medium, the Pollen grain through ofthe pollen tube. ™ale gamete is lent pollen grain germinates. The tube cell enlarges and comes out of the one of the germ pores to form a pollen tube. The tube nucleus descends to the tip ‘The generative cell also passes into it. It soon divides into two male gametes. Each ticular to spherical in outline.22 Laboratory, Manual in Biology. Comprehensive , Exine Intine Tube nucleus Fig. 1.1. Germination of pollen grains. PRECAUTIONS 1. Flowers should be freshly plucked. 2. Use clean slide to observe the pollen grains. Qi. Ans. Q2. Ans. Q.3. Ans. Q4. Qs. Ans. Q.6. Ans. VIVA VOCE What is the shape of a pollen grain ? It is commonly globular in outline, though several other shapes are also found. What is palynology 7 ‘The study of pollen grains is called palynology. What is the composition of wall of pollen grain ? It is made up of two layers, outer exine and inner intine. What is the chemical nature of the two layers of the wall of pollen grain? » Tntine is pecto-cellulosic in nature and exine is made of highly resistant fatty subst®™ called sporopollenin. What is tectum ? It is the discontinuous surface layer of the exine of the pollen grain wall, which prové# characteristic sculpturing or designs over the surface of pollen grain. What is the importance of tectum to a taxonomist ? : of Tt can help a taxonomiist to identify the pollen grains and refer them to their family, 6e™™* species.Study of Pollen Germination and Growth of Pollen Tube 1, Pollen grains are the male reproductive structures of spermatophytes. A pollen grain is a partly germinated microspore representing the male gametophyte. 2. Each pollen grain ofa flowering plant (angiosperm) possesses two cells—(i) vegetative cell and (ii) generative cell. It has two layered wall—(j) the exine, which is the outer layer and chiefly composed of sporopollenin and (ii) the intine, which is the inner layer and chiefly composed of plecto-cellulose. At one or more places the exine is very thin or absent. These regions are called apertures through which the pollen tube emerges at the time of germination. 3. The germination of pollen grain occurs, when it is deposited to the receptive surface of the carpel called stigma through the process of pollination. 4, Onthe stigma, the pollen grain germinates and gives out a pollen tube from its vegetative cell. ‘The pollen tube grows between cells of stigma and transmitting tissue of the style. Later, the generative cell moves down to the pollen tube and devide to give rise two male nuclei (male gametes). 5. ‘The germination of pollen grain and the growth of pollen tube can be studied through a teased preparation/longitudinal section of a pollinated carpel. (EXPERIMENT 2.1_) AIM: To study the pollen germination and growth of pollen tube in a pollinated pistil (in Portulaca/ grass or any other. suitable flower). REQUIREMENTS Fresh pollinated flowers of Portulaca/grass or any other suitable flower, glass slide, coverslip, Needles, forceps, brush, dropper, safranin, glycerine, petridish, water, blotting paper, microscope etc. PROCEDURE 1. Take out the pollinated carpel from the flower of Portulaca/grass or any other suitable flower and place it on a glass slide in a drop of water. Gently tease it with the help of needles or pick Up the carpel from the flower and cut a longitudinal section of it. Place the section on a glass slide in a drop of water.“ Pollen grain Pollen tube Style A Fig. 2.1. Pollen germination. A. Pollen grains germinating ©n stigma (a teased Preparation). B. Growth of pollen tube in the carpel (LS). v PRECAUTIONS 1 2. a: Only pollinated carpels should be selected for the experiment,Study of Gamete Development in Mouse (Mammal) INTRODUCTION Gametes are the sex cells involved in the process of sexual reproduction. ‘The gametes differ from all other cells (= somatic cells) of the body in that their nuclei contain only half the number of chromosomes found in the nuclei of somatic cells. N 3. Meiosis forms the most significant part of process of gametogenesis. 4, Gametogenesis for the formation of sperms is termed spermatogenesis, while that of ova is called oogenesis. 5. Spermatogenesis occurs in the seminiferous tubules of the testes, whereas oogenesis occurs in the ovaries. ~ EXPERIMENT 3.1 = e AIM: To study and identify the stages of gamete develo, testis and L.S. of ovary through permanent slide. REQUIREMENTS Permanent slide of T.S. of testis and L.S. of ovary, ‘ferocepure Fix the permanent slide under the microscope, under high power. pment in mouse (mammal) i.e., T.S. of microscope. First observe it under the low power and then OBSERVATION TS. of Testis i 2 3 ‘The testis of a mouse (mammal) is covered by a thick fibrous tissue called tunica albuginea. ‘The testis consists of numerous seminiferous tubules embedded in the interstitial tissue, Various types of germinal cells are present from outside towards lumen inthe following sequence. Spermatogonia ~» Spermatocytes -» Spermatids -» Spermatozoa —» Sper™®- 4. Between the germinal cells, pyramid shaped cells called sertoli cells are presentrrr for spotting 47 4 ange number of spermatozoa with their heads embedded in sertoli i 7: eee eele in sertoli cells are present in the | es qpeinterstitial tissue also contain leydigs cells, which produce male sex hormone testosterone. Interstitial cells ion of testis of mouse (mammal). 3.1. A.A Part of transverse secti us tubule (enlarged). Fig. B. Sectional view of a part of seminifero\ VS. of Ovary «. Amouse ovary is a solid structure bounded by germinal epithelium followed by a thick layer of fibrous tissue, the tunica albuginia. ‘Secondary Blood vessel Tertiary follicle Mosovaram perteneum Graafian follicle Corpus albicans. Corpus luteum Ruptured follicle Fig. 3.2. A section of ovary of mouse (mammal).48 Comprehensive Laboratory Manual in Biology—j ‘The ovary consists of outer cortex and inner medulla. ‘The medulla contains many rounded or oval bodies called ovarian or Graafian follicles at various stages of development. ‘The medulla also contains blood vessels, nerves fibres and some smooth muscles. Each follicle contains a large ovum surrounded by many layers of follicle cells. ‘The cortex contains young and mature follicles. ‘The cortex may also contain a large mass of yellow cells termed corpus luteum, formed in an empty Graafian follicle after the release of its ovum. PRECAUTIONS i a Qn Ans. Q2. Ans. Q.3. Qa. Ans. Qs. Ans. Power and then under the high power of the microscope. Use fine adjustment of the microscope for focussing the slide under high power. VIVA VOCE What is gametogenesis? Gametogenesis is the process by which male and ova are formed respectively i in the tes What is spermatogenesis ? ‘The process of. formation of g female se: x cells or gametes ie., sperms and tes and ovaries, Perms in the testis is called spermatogenesis, - What is oogenesis ? Ans, ‘The process of formation of ova in the ovary is called oogenesis. What are the main parts of a spermatozoa ? Atypical mammalian spermatozoa consists of a head, neck At what stage does the huma: n ovum is released from ‘The ovum is released from the ovary in the secondary oo, middle piece and tail, the ovary? cyte stage,Study of Blastula INTRODUCTION 1. Soon after fertilization, the zygote undergoes repeated divisions called cleavage. 2. Cleavage includes a series of successive and rapid mitotic divisions which transform single celled zygote into a multicellular structure called blastula (blastocyst). 3. Cleavage occurs in the upper portion of the Fallopian tube. It results into a solid mass of cells called morula. 4, At the next stage of development which produces an embryo with about sixty four cells called blastula or blastodermic vesicle. ——— ( EXPERIMENT 5.1 ) Nie AIM: To study T.S. of blastula through permanent slide. REQUIREMENTS Permanent slide of blastula, microscope. PROCEDURE K Fix the slide of T.S. of blastula under microscope. First observe the slide under low power and then under high power of the microscope. (Fovinatvenaney eecetitit pellucida Albuminous layer around the zona Fig. 5.1. T.S, of blastula.56 wy ~~ Comprehensive Laboratory Manual in Biology—XIl OBSERVATIONS 1 2. 5. Itis a spherical mass of about sixty four cells. Itis composed of an outer envelope of cells, the trophoblast or trophoectoderm and inner cell mass (= embryoblast). Within the envelope there is a fluid filled cavity called blastocoel. ‘The side of the blastocyst to which the inner cell mass is attached is called the embryonic or animal pole, while the opposite side is the abembryonic pole. The inner cell mass is the precursor of the embryo. PRECAUTIONS de 2 Qi. Ans. Q2 Ans. Q3. Ans. Qa Ans. as. Ans. | ep» First focus the slide under low power and then under the high power of the microscope. Use fine adjustment while focussing the slide under high power of the microscope. VIVA VOCE What is cleavage ? It is a series of rapid mitotic divisions of the zygote which convert the single called zygote into a multicellular structure called blastula or blastocyst. What is morula? ‘The solid mass of cells formed after cleavage is called morula. What is blastocyst ? Itisa stage of embryonic development consi Mass and a fluid filled cavity called blastoco What is implantation ? isting of an outer envelope of cells, the inner cell el, Itis the attachment of the blastocyst to the uterine wall. When does implantation occur in human beings ? Ttoccurs after 7 days of fertilization, .a Exercise on Controlled Pollination INTRODUCTION 1. Plant breeding is a science of changing and improving the heredity of plants and production of new varieties which are far better than original type. 2. Plantintroduction and acclimatization, selection, hybridization, mutation, breeding and induced polyploidy are the main methods of plant/crop improvement. Hybridization is a method by which improved varieties of economically important plants/crops are produced by crossing two or more genetically different plants. 4, The main steps of hybridization are : (i) Selection of parents (ii) Selfing of parents (ii) Emasculation (iv) Bagging, tagging and labelling (v) Crossing (vi) Collecting hybrid seeds and growing F, generation (vii) Trials, multiplication and distribution. ( EXPERIMENT 8.1.) AIM: To comment on the exercises of hybridization (emasculation, tagging and baggi “ models/charts. , tagging and bagging) through Z 41, Emasculation Identification. Forceps or scissors method of emasculation, Comment (i) This method is employed in the crops having flowers of sufficiently large size lint cotton. (ii) The instrument used in this method include pocket lens, camel hair brush etc. forceps, needle, scissors, scalpel, (iii) In this process anthers are removed from the flowers before their maturation (iv) The anthers are cut with the help of sterilized forceps or scissors, Ld } 3m67 xperiment for Spotting . Removal of anthers (Emasculation) Parent Fig. 8.2. Forceps or scissors method of emasculation.é Comprehensive Laboratory Manual in Biology—Xll _/ Identification. Hot or cold water and alcohol emasculation. Comments \~ (i) This method of emasculation is employed the crops having small flowers like paddy, sorghum ete. (i) In this method the penicles (clusters of flowers) are dipped in hot water (40°C-45°C) for 1-10 minutes to kill the anthers. (iii) In the same way emasculation is done with cold water or alcohol. Fig. 8.3. Methods of emasculation. A. Single spikelet of paddy; B. Removal of anther after opening of a flower; C. Emasculation by hot water. . Tagging and Bagging Identification. Bagging, tagging and labelling. Comment (@ After emasculation, the flowers are covered with small bags to prevent pollination with undesired pollen grains, (ii) These bags are made up of polythene, Paper, muslin cloth or parchment Paper. (iii) The bags are punctured or made Perforated so as to provide aeration to the flowers, (iv) The flowers of male parents are also protected in bags to prevent mixin of their pollen grain with foreign pollens, (v) After dusting of the desired pollen grains on the emasculated flower the bags are retagged. (vi) Alabel of paper is tagged on the plant which displays the dat of emasculation, crossing and brief account of the parents, . a wt aa»corso G4. Ans, Qa Ans, Qa, Ans, A B c Fig. 8.4. Bagging on different crop plants. VIVA VOCE What is plant breeding ? Itisa technique of development of improved varieties of crops. Which is the oldest method of plant improvement ? Selection. What are the objectives of plant breeding ? ‘The main objectives of plant breeding are bette yield and quality, uniformity, resistance to diseases and pests, tolerance t climatic variations, consumers demand and change in growth habit.an, Study of Models/ Specimens Showing Symbiotic and Parasitic Association INTRODUCTION Innature no species can live in isolation. 1 AJ (IME Study of sym For any species there must be at least one species on which it can feed. ‘Animals, plants and microbes do not and can not live in isolation, but interact in various ways to form biological community. Populations of different species often interact or effect each other in various ways in their habitats. Such interactions are important for survival of different species and the community as a whole. Such interactions in a community include predation, parasitism, symbiosis (mutualism), competition, commensalism etc. san interaction between two organisms of different species where both ted and none of the two capable of living separately. Parasitism is a relationship between two living organisms of different species in which one organism called parasite, obtains its food directly from another living organism called host. ‘The parasite spends a part or whole of its life on or in the body of the host. Symbiosis (mutualism) is the partners are benefitt EXPERIMENT 10.1 } biotic and parasitic interactions among the organisms through models/ specimens, and comment upon them. oot of a Leguminous plant bearing nodules Comments “Temwonked es of lgrunien plait taeracntpaient ic. Saunier emia with nitrogen fixing bacteria - Rhizobium. ‘The bacteria — Rhizobium carry out nitrogen fixation in root nodules of leguminous plants. ‘The bacteria also live freely in the soil but are unable to fix nitrogen. ‘The nitrogen fixation property develops only inside root nodules. weer ‘The roots of leguminous plant provide food and shelter to the bacteria. inoe 76 Comprehensies Laboratory Manual in Biology— xj, ‘A major part of nitrogen fixed by bacteria is handed over to the leguminous plant. ‘Thus, both the partners (Le. the bacteria and the leguminous plant) are benefitted in this association. Rhizobium enters into the roots of a legume plant i of a legume plant from the soil through root hair and pri small outgrowth on the root called nodules. . aa ‘Some of the bacteria enlarges to become membrane bound structures called bacteroides, ‘The bacteriods fix atmospheric nitrogen under anaerobic condition, u ‘The anaerobic condition in the cells of root nodule: r ° of root nodules is provided by pink coloured pig Jeg-haemoglobin present in the cells of leguminous plant. a — Host ce © Fig. 10.1. Symbiotic nitrogen fixation. A, nodulated Cal hans eter of egure B.S. nodule Experiment for Spotting Letfen ‘Comments |. Lichens are composite or dual organisms representing a symbiotic association between a fungus andan alga. 9, The fungal partner is called a mycobiont, which is either a member of ascomycetes or basidiomycetes. 45, The algal partner is called a phycobiont, which is either a green alga or blue green alga (cyanobacteria). ‘The relationship between the fungus and the alga in a lichen is that of mutual benefit, (mutualism), popularly called symbiosis. 5. ‘The fungus provides structural covering, absorbs water and minerals and fixes thelichen tothe substratum, 6. The alga prepares food by photosynthesis, and also fixes atmospheric nitrogen, when itis @ ‘cyanobacterium. Depending on the shape, three morphological forms of lichens are recognised. These are () Crastose lichens (thin membranous forms) (i) Foliose lichens (with lobed, flat leaf like body) and (i) Fruticose lichens (with well branched small bushy body). “ q—Seredium : - ag toy “Upper Fungal ‘Cenex ayer, Algal Layer Vaan J Lower Fungal — (Cortex Layer) im = Rhizines Fig, 10.2. AC. Different types of Lichens. A. Crustose (Graphis), 8. Foliose (Parmelia), C.Fruticose (Usnea}, D. VS. ofa lichen thallus.EE 78 Comprehensive Laboratory Manual in Biology—xy Cuscuta on a host plant Comments ] 1. Cuscuta (Amarbel or Aakashbel) shows parasitic association with some other flowering plant, 2. Parasitic association or parasitism is an association between two living organisms of two different species in which one organism called parasite obtains its food directly from another living organism called host. 3. Cuscuta has non-green stems and bears non-photosynthetic scale leaves. It does not have any connection with the soil. 4. Cuscuta has haustorial roots called sucking roots or suckers, which penetrate into the host plant and make connection with xylem (water channel) and phloem (food channel) of the host to absorb both water and food. Flowers Haustorial Roots Parasite Haustorial B Roots Host C Scale Leaf Fig. 10.3. Cuscuta. A, parasite on host. B, part of Cuscuta on host showing flowers and haustoria. C, stem of Cuscuta showing haustoria. Adhesive Tissue Phloem of Host ——— xylem of Host Fig. 10.4. Haustorial connection between Cuscuta and host.