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Question Bank, Pollination and Fertilisation, 1. Define pollination. How does it differ from fertilisation?, Ans. Pollination is the transfer of pollen grains from the anthers to, the stigma., Fertilisation follows successful pollination and is the fusion of, the nuclei of two dissimilar sexual units called the male and, female gametes., While pollination results in germination of pollen grains,, formation of pollen tubes and the entry of pollen tube inside, the ovary upto the ovules, fertilisation results in the formation, of zygote and subsequently seeds., 2. Give two advantages and two disadvantages each of self and, cross-pollination., Ans. Advantages of Self-pollination, (i) Self-pollination being almost certain in bisexual flowers, ensures continuity of the race., (ii) Self-pollination helps to preserve the parental characters, as the gametes from the same flower are involved., (iii) It is economical as the plants do not have to produce, pollen grains in large quantity., (iv) Flowers need not be showy, nor they need to produce, nectar or scent., Disadvantages of Self-pollination, (i) New varieties cannot be obtained by self-pollination., (ii) The genetic defects of the breed cannot be removed., (iii) Repeated self-pollination leads to loss of vigour and, vitality of the species. Seeds produced are smaller and, weaker., , Biology Class-IX, , 1, , Question Bank

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Advantages of Cross-pollination, (i) Cross-pollination results in healthier offsprings., (ii) Seeds produced by cross-pollination have much better, germinating capacity., (iii) More abundant and viable seeds are produced., (iv) Variations are introduced by cross-pollination., Disadvantages of Cross-pollination, (i) Plants have to depend on external agencies for pollination,, which may or may not be available at the proper time., (ii) The pollen grains have to be produced in large quantity to, ensure pollination. Thus, lot of pollen is wasted., (iii) The process is less economical as various devices have to, be adopted by the flowers to attract pollinating agents like, the flowers have to be large, coloured, showy, scented, and nectar producing., 3. State four differences between insect and wind-pollinated, flowers., Ans. Differences between Insect-and Wind-pollinated Flowers, Insect-pollinated flowers, 1. Flowers have large and brightly, coloured petals, 2. Produce scent and nectar., 3. Pollen grains are rough and sticky, 4. Pollen grains are produced in, Small quantity., 5. Filaments short., , Wind-pollinated flowers, Flowers are small and do not have, showy petals., Do not produce scent and nectar., Pollen grains are light and dry., Produced in large quantity., Filaments long to expose anthers in, the air., Stigmas are large and feathery., , 6. Stigmas are sticky, flat or knoblike., 7. Essential whorls are not much, exposed., 8. Nectar guides are present on the, petals., Examples - Salvia, pea, petunia., , Biology Class-IX, , Male and female parts are exposed to, wind., Nectar guides generally absent., Examples - Maize, wheat, pine., , 2, , Question Bank

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4. Give two examples each of wind, water and insect pollinated, flowers., Ans. Wind-pollinated flowers - Maize, pine., Water-pollinated flowers - Hydrilla, Vallisneria., Insect-pollinated flowers - Sweet pea, Salvia., 5. Normally, sepals fall after fertilisation. Name two fruits in, which the sepals persist., Ans. Brinjal, tomato., 6. In brief explain the method of pollination in a named flower., Ans. The students can answer this question by taking any of the, flowering examples:, (i) Salvia (ii) Sweet pea, (iii) Maize, (iv) Vallisneria., All these are mentioned below for easy reference., Insect-Pollination in Salvia, In Salvia pollination occurs by bees. The flower has bilipped, (bilabiate) corolla with two epipetalous stamens., The stamen and the style are hidden in upper lip forming a, hood. The lower lip serves as landing place for the bee to, alight on. The flower is protandrous, i.e., the stamen matures, earlier than the carpel. The filament of stamen is very short, and its upper end is connected to long curved connective. The, connective acts as a lever whose unequal arms bear the two, anther lobes; thus, the anther lobes are widely separated. The, upper (outer) lobe is fertile while the lower one is sterile, (without pollen grains). The sterile lobes of both anthers are, situated at the corolla mouth which blocks the way to the, nectar as the nectary is located at the base of the ovary., When the bee enters the flower it pushes the lower sterile lobe,, the long connective swings downward resulting in the bending, of the stamen down with a jerk to sprinkle pollen grain on its, back. When the bee visits another flower where stigma is ripe, and is protruding out of the hood of upper lip, the pollen laiden, back brushes against the stigma and the pollen grains stick to, Biology Class-IX, , 3, , Question Bank

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it. This is how pollination is brought about in Salvia, and is, known as the ‘lever mechanism’., , Showing pollination in Salvia : A-B. L.S. of flower showing, immature gynoecium and movement of stamen when pressed, by insect C. A bee entering the corolla and getting dusted with, pollen D. Bee entering another flower and transferring the, pollen grains to stigma., Pollination in Sweet pea (Lathyrus), The sweet pea is pollinated by bumble bee. The flower has, five petals—one large innermost standard, two lateral petals, forming wing and the two innermost petals called the keel, petals. There are 10 stamens, nine of which are fused together, to form a staminal tube which encloses the ovary and part of, style., , Showing structure of flower of sweet pea (A-F)., Biology Class-IX, , 4, , Question Bank

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The bees are attracted by colour, scent and nectar. The two, wing petals act as a landing platform for the bee. When a bee, lands on the wing petals, its weight pulls them down along, with the keel petals. The style and stigma emerge out touching, the under surface of the bee that may be carrying the pollen, from another flower, thus causing cross-pollination. Also, as, the bee searches for nectar at the base of the ovary, the anthers, may rub pollen grains against the body of the bee for crosspollinating another flower., Wind-Pollination in Maize, In maize plant, the male flowers are borne at the apex of the, plant and the female flowers are borne near the base in the axil, of the leaf. The male flowers produce large quantities of pollen, grains. As the anthers burst, the pollen grains are blown by air, current and many of them may fall on the feathery stigmas of, the neighbouring plants which have long hanging styles with, feathery stigma, thus bringing about cross-pollination., , Showing pollination in maize, , Biology Class-IX, , 5, , Question Bank

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Pollination in Vallisneria, Vallisneria is a unisexual submerged plant. The female flowers, have long coiling stalks which bring the flowers on the surface, of water. The male flowers grow under water. When ripe, the, male flowers get detached from the plant and float on the, surface of water. The free floating male flowers cluster around, female flowers, their anthers burst and the pollen grains get, attached to the stigma of female flowers. After pollination, the, stalk of the female flower gets coiled, pulling the female, flower once again under water., , Showing Vallisneria – a hydrophilous plant. A. Female plant B. Male plant., , Biology Class-IX, , 6, , Question Bank

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7. State any three devices found in flowers which favour crosspollination., Ans. Devices which favour cross-pollination :, (i) Unisexuality : The unisexual flowers (male or female), may be borne on the same plant (as in maize, castor,, cucumber) or on two separate plants (as in palm, mulberry,, papaya). This condition favours cross-pollination., (ii) Self Sterility : In this condition, the pollen grains of a, flower do not germinate on the stigma of the same flower but, germinate on the stigma of a flower borne by another plant of, the same species; thus ensuring cross-pollination., Examples - Apple, grape, rye., (iii) Dichogamy : The flowers are bisexual, but stamens and, carpels mature at different times. This condition is known as, dichogamy which stands as a barrier to self-pollination., There are two states of dichogamy., (a) Protogyny (Protos = first; gyne = female) : In this, case, gynoecium matures earlier than the anthers of, the same flower and the stigma receives the pollen, grains brought from another flower., Examples - Peepal, custard apple., (b) Protoandry (Protos = first; andros = male): When, the stamens mature earlier than the gynoecium of the, same flower, the pollen grains are carried over to the, stigma of another flower, as in pea, sunflower, salvia., (iv) Herkogamy (Herkos = barrier) : In some bisexual, flowers, some sort of barrier develops between stamens and, the pistil of the same flower, thereby preventing selfpollination. For example, a hood covering the stigma acts as a, barrier in pansy flowers. In Gloriosa, the stamens liberate the, pollen grains on the outside, so that they are not able to land on, the stigma of the same flower., , Biology Class-IX, , 7, , Question Bank

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(v) Heterostyly (Heteros = different) : Some plants bear, flowers of different forms. One form bears long stamens and, short style, and the other form bears short stamens and long, style. This condition favours cross-pollination. Dimorphic, heterostyly is shown by primrose and oxalis., , Heterostyly in primrose (Primula) flowers, , 8. Mention whether the following statements are True (T) or, False (F) :, (i) Fertilisation is fusion of anther and stigma., (ii) Cross-pollination always occurs in unisexual flowers., (iii) The generative nucleus in the pollen grain develops into, two male gametes., (iv) In maize, the pollination is brought about by insects., (v) Anemophilous flowers are large and bright., (vi) Vallisneria flowers are pollinated by wind., Ans. (i) F (ii) F (iii) T (iv) F (v) F (vi) F, 9. Name the floral parts which develop into following structures :, (i) seed, (ii) pericarp, (iii) seed coat, (iv) fruit., Ans. (i) Seed, from ovule, (ii) Pericarp, from ovary wall, (iii) Seed coat, from Integuments of ovule, (iv) Fruit, from ovary., , Biology Class-IX, , 8, , Question Bank

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10. Write a short note on artificial-pollination., Ans. Artificial pollination, Man plays an important role in, bringing about pollination artificially., For this, better yielding and better, quality flowers are selected. Pollen, grains from the ripe anthers are carefully, removed and are dropped on the mature, stigma of other plant of the same or related, species. These pollinated flowers are now, covered with polythene bags till fruits and Showing artificial pollination in pea, seeds are produced. The seeds when sown, in next season produce offsprings with slight, variations. If this process is repeated for some, generations, new varieties could be produced., This method is very commonly practised in, garden plants such as pansy and stock or in, crops like wheat and maize., , Biology Class-IX, , 9, , Question Bank

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11. What is the function of pollen tube? Trace its path from stigma, to the female gamete by means of a diagram., Ans. Functions of the pollen tube, (i) To carry the male gametes upto the embryo sac (inside the, ovule) where female gamete is present., (ii) To produce enzymes which dissolve the tissues of the, style so that the pollen tube can travel the whole length of, the style and reach the ovule., , Showing the path of pollen tube from stigma to the female gamete (egg)., , 12. Explain the following terms :, (i) Anemophilous flower (ii) Double fertilisation, (iii) Gametes, (iv) Oospore, (v) Nectar guides, (vi) Triple fusion, Ans. (i) Anemophilous flower : Wind-pollinated flower; wind, brings about cross-pollination; flowers are usually small,, inconspicuous and unattractive; pollen grains are produced, in large number., (ii) Double fertilisation : In flowering plants, each pollen, grain produces two male gametes. One male gamete fuses, with the female gamete, and the other fuses with the, secondary nucleus. Since there are two fertilisations, it is, called double fertilisation., Biology Class-IX, , 10, , Question Bank

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(iii) Gametes : An haploid cell taking part in sexual, reproduction; two gamete nuclei (male and female) fuse, during fertilisation, to initiate the development of a new, individual., (iv) Oospore : The product of fusion of male gamete with the, female gamete, i.e. fertilisation, is called oospore., (v) Nectar guides : Some flowers bear markings on the petals, which lead to the nectaries present in the flower. These, markings guide the insects towards the nectaries, and, hence, are called nectar guides. The nectar guides help in, pollination., (vi) Triple Fusion : The fusion of one of the male gametes, with secondary nucleus is termed as triple fusion, as it, involves the fusion of three nuclei., 13. Distinguish between the following :, (i) Protandry and Protogyny, (ii) Self-pollination and Cross-pollination, (iii) Fruit and Seed, (iv) Tube nucleus and Generative nucleus, (v) Ovule and Seed., Ans. (i) Differences between Protandry and Protogyny, (Both are contrivances for cross-pollination), Protandry, The stamens in a bisexual flower, mature earlier than the gynoecium of, the same flower, so the pollen grains, are carried, over to the stigma of another flower., , Biology Class-IX, , Protogyny, The gynoecium in a bisexual flower, matures earlier than the stamens of, the same flower, so the stigma, receives the pollen grains brought, from another flower., , 11, , Question Bank

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(ii) Differences between Self-pollination and Crosspollination., Self-pollination, 1. Self-pollination occurs within a, flower or between two flowers of, the same plant., 2. Flowers do not depend on other, agencies for pollination., 3. Pollen grains are produced in, small number., 4. No wastage of pollen grains, occurs and thus economical., 5. Flowers are not attractive, nor do, they produce nectar., , Cross-pollination, Cross-pollination occurs between, two flowers borne on different plants, of the same species., Agents such as insects, water and, wind are required for pollination., Produced in large numbers., , Wastage of pollen grains occurs,, hence, uneconomical., Flowers attract insects by various, means like coloured petals, scent and, nectar., 6. The offsprings produced are of the The offsprings produced may show, same genetic makeup, so purity of variations and differ in genetic, makeup., the race is maintained., , (iii) Differences between Fruit and Seed, Fruit is the structure developing from the complete ovary,, while a seed develops from the ovule., (iv) Differences between Tube nucleus and Generative nucleus, (Both are nuclei present inside the pollen grain), (a) The generative nucleus after germination of pollen, grains divides into two male gametes inside the pollen, tube, whereas the tube nucleus does not divide., (b) In angiosperms, the two male gametes take part in the, two fertilisations (double fertilisation) while tube, nucleus is not involved in fertilisation., , Biology Class-IX, , 12, , Question Bank

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(v) Differences between Ovule and Seed, Ovule, 1. Ovule is a structure contained in, the ovary., 2. Inside the ovule, embryo sac, containing the female gamete (or, egg) is present., 3. It is a pre-fertilisation female, reproductive structure., , Seed, Seed is present inside the fruit in, angiosperms., It develops after fertilisation of the, female gamete with the male gamete., It is a post-fertilisation product., , 14. Describe the events taking place between pollination and, fertilisation., Ans. Events between Pollination and Fertilisation., After the pollen grains are deposited on, the stigma, the pollen grains absorb water, and sugar from the surface of stigma and, swell up. From one of the germ pores, the, intine comes out into a fine tube called pollen, tube. This tube produces enzymes at the tip, and dissolves the tissues of the style, as it grows. Eventually, it travels down the, whole length of the style into ovary., Showing Pollen germination, In the meantime, inside the pollen tube, the, generative nucleus divides into two male gametes., The pollen tube carrying the two male gametes enters the, embryo sac through the micropyle and its tip dissolves. The, two male gametes are liberated inside the embryo sac., One male gamete fuses with the egg to form zygote which, grows into an embryo and finally into a new plant. The other, male gamete fuses with the secondary, nucleus to form the endosperm, which provides nourishment, to the growing embryo., The fusion of the male gamete with the female gamete is, called fertilisation. The process, in fact, involves two, Biology Class-IX, , 13, , Question Bank

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fertilisations — one between male and female gametes and the, other between the male gamete and the secondary nucleus. It, is, therefore, also termed double fertilisation., 15. Draw a labelled diagram of ovule as seen in a section., Ans., , Showing ovule in section, , 16. Describe the post-fertilisation changes taking place in an, ovary., Ans. Post-fertilisation changes, After fertilisation has taken place, the sepals, petals, stamens,, style and stigma wither away and usually fall off. In some, cases, the sepals may persist in a shrivelled form as in tomato,, peas, or become fleshy as in brinjal. The ovary enlarges, considerably., Inside the ovule, the zygote undergoes cell divisions to form, the embryo, consisting of the radicle and the plumule., The changes occurring in the ovary after fertilisation are, outlined in the following table., , Biology Class-IX, , 14, , Question Bank

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Table showing changes occurring in the ovary after fertilisation., Ovary, 1. Ovary wall, , 2. Ovule, (a) funicle, (b) hilum, (c) micropyle, (d) integuments, (i) outer integument, (ii) inner integument, (e) nucellus, (f) embryo sac, (i) antipodals, (ii) egg cell, (iii) secondary nucleus, , Fruit, 1. Pericarp (fruit wall), (a) epicarp, (b) mesocarp, (c) endocarp, 2. Seed, (a) stalk, (b) hilum, (c) micropyle, (d) seed coat, (i) testa, (ii) tegmen, (e) generally degenerates, if, persists, called perisperm., (i) degenerate, (ii) zygote –→ embryo, (iii) endosperm, , 17. Mention characteristics of entomophilous and anemophilous, flowers., Ans. (a) Entomophilous flowers, Entomophilous flowers have various adaptations for attracting, the insects., 1. The flowers are large-sized and brightly coloured to attract, the insects., 2. When flowers are not conspicuous, other parts become, coloured and showy. For example, in bougainvillea bracts, become colourful., 3. They produce nectar or scent which attracts insects, as in, jasmine., 4. Some flowers bear markings or lines on the petals which, act as nectar guides that lead the insects to the nectaries, as, in pansy., , Biology Class-IX, , 15, , Question Bank

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5. The pollen grains of entomophilous flowers are either, rough or sticky so that they adhere to the body of insects, easily., 6. The stigma is sticky, flat or lobed., 7. When the flowers are small, they form inflorescence to, make them conspicuous and attractive. Common example, is sunflower., (b) Anemophilous flowers, Anemophilous or wind-pollinated flowers have following, characteristics :, 1. The flowers are usually small, inconspicuous and, unattractive., 2. They do not produce scent or nectar., 3. The anthers produce large quantity of pollen grains., 4. The stamens are long and protrude out of the flower to be, exposed to wind., 5. Anthers are large protruding out of the flowers and loosely, attached to the long filaments so that they can easily be, moved by the wind., 6. The pollen grains are smooth, light and dry and sometimes, provided with wings as in pine so that they can easily be, carried by wind to long distances., 7. Stigma is comparatively large branched and often feathery to, trap the pollen grains, e.g. maize, rice, grasses, sugar cane,, pine., 18. The diagram alongside shows a, section through a flower at two, stages of development., Observe the diagram and answer, the following questions :, (a) Write down two features in the, diagram to show that the, flower is insect-pollinated., A Section of flower, Biology Class-IX, , 16, , Question Bank

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(b) What information shown in the, diagrams would suggest that, cross-pollination takes place in the flower?, Ans. (a) (i) Nectary is present., (ii) Anthers are present inside the corolla which is, bilipped at the upper end, thus aiding the insect in, reaching upto the nectary, and also getting brushed with, the pollen., (b) Flower shows protoandry as the stamens have shed the, pollen grains even before the stigma is opened. This, feature suggests cross-pollination., 19. Fill in the blanks with appropriate word given in the brackets., (i) Cross-pollination takes place in all ________ plants., (monoecious/dioecious), (ii) Bougainvillea flowers are pollinated by _______., (wind/insects/water), (iii) Double fertilisation is common in ______., (gymnosperms/angiosperms), (iv) Salvia is a ______ flower., (entomophilous/ornithophilous/hydrophilous), (v) After fertilisation, the _________ becomes the fruit and, the __________ becomes the seed., (ovule / ovary / integuments), Ans. (i) dioecious, (ii) insects, (iii) angiosperms, (iv) entomophilous, (v) ovary, ovule., , Biology Class-IX, , 17, , Question Bank