{"id":35717,"date":"2022-09-27T10:26:13","date_gmt":"2022-09-27T04:56:13","guid":{"rendered":"https:\/\/apboardsolutions.guru\/?p=35717"},"modified":"2022-09-27T10:26:13","modified_gmt":"2022-09-27T04:56:13","slug":"ap-inter-1st-year-botany-study-material-chapter-7","status":"publish","type":"post","link":"https:\/\/apboardsolutions.guru\/ap-inter-1st-year-botany-study-material-chapter-7\/","title":{"rendered":"AP Inter 1st Year Botany Study Material Chapter 7 Sexual Reproduction in Flowering Plants"},"content":{"rendered":"

Andhra Pradesh BIEAP AP Inter 1st Year Botany Study Material<\/a> 7th Lesson Sexual Reproduction in Flowering Plants Textbook Questions and Answers.<\/p>\n

AP Inter 1st Year Botany Study Material 7th Lesson Sexual Reproduction in Flowering Plants<\/h2>\n

Very Short Answer Questions<\/span><\/p>\n

Question 1.
\nName the component cells of the “egg apparatus” in an embryo sac.
\nAnswer:
\nOne egg cell and two synergids.<\/p>\n

Question 2.
\nName the part of gynoecium that determines the compatible nature of pollen grain.
\nAnswer:
\nStigma.<\/p>\n

Question 3.
\nName the common functions that cotyledons and nucellus perform.
\nAnswer:
\nCotyledons and nucellus are often fleshy and full of reserve food materials.<\/p>\n

Question 4.
\nName the parts of pistil which develop into fruit and seeds.
\nAnswer:
\nOvary of the pistil develops into fruit and ovule of the pistil develops into seed.<\/p>\n

Question 5.
\nIn case of polyembryony, if an embryo develops from the synergid and another from the nucellus which is haploid and which is diploid?
\nAnswer:
\nIn case of polyembryony, the embryo develops from synergid is haploid and the embryo develops from nucellus is Diploid.<\/p>\n

\"AP<\/p>\n

Question 6.
\nCan an unfertilised, apomictic embryo sac give rise to a diploid embryo? If yes, then how?
\nAnswer:
\nYes. Unfertilised apomictic embryosac give rise to a diploid embryo. The diploid Egg cell is formed without Meiosis and develop into the embryo without fertilisation.<\/p>\n

Question 7.
\nWhich are the three cells found in a pollen grain when it is shed at the three celled stage?
\nAnswer:
\nTwo male gametes and one vegetative cell.<\/p>\n

Question 8.
\nWhat is self-incompatibility?
\nAnswer:
\nIncompatibility of pollengrains to germinate on the stigma of the same flower is called self – incompatibility of self sterility.<\/p>\n

Question 9.
\nName the type of pollination in self incompatible plants.
\nAnswer:
\nCross pollination is seen in self-incompatible plants.
\nEx : Abutilon.<\/p>\n

Question 10.
\nDraw the diagram of a mature embryo sac and show its 8-nucleate, 7 – celled, nature. Show the following parts : antiopodals, synergids, egg, central cell, polar nuclei.
\nAnswer:
\n\"AP
\n(a) Parts of the ovule showing a large megaspore mother cell, a dyad and a tetrad of megaspores.
\n(b) 2, 4 and 8-nucleate stages of embryo sac and a mature embryo sac
\n(c) A diagrammatic representation of the mature embryo sac.<\/p>\n

Question 11.
\nWhich is the triploid tissue in a fertilized ovule? How is the triploid condition achieved?
\nAnswer:
\nEndosperm. It is formed by the fusion of 2nd<\/sup> male gamete with Diploid secondary nucleus to form PEN which changes into endosperm.<\/p>\n

\"AP<\/p>\n

Question 12.
\nAre pollination and fertilisation necessary in apomixis? Give reasons.
\nAnswer:
\nPollination and fertilization are not necessary in Apomixis. The diploid egg cell is formed without meiosis and develops into embryo without fertilisation. It is an assured reproduction in the absence of pollinators.<\/p>\n

Question 13.
\nHow is pollination carried out in water plants?
\nAnswer:
\nIn vallisnaria, pollination occurs on the water surface (Epihydrophily). Inzoostera, pollination occurs under water (Hypohydrophily). In water hyacinth and water lily, the pollination occurs by Insects.<\/p>\n

Question 14.
\nWhat is the function of the two male gametes produced by each pollen grain in angiosperms.
\nAnswer:
\nOf the two male gametes produced by each pollen grain, one male gamete fuses with the egg to form Diploid zygote (Syngamy). The second male gamete fuses with the secondary nucleus to form primary endosperm nucleus (Tripple fusion).<\/p>\n

Question 15.
\nName the parts of an angiosperm flower in which development of male and female gametophyte take place.
\nAnswer:
\nMicrospore develops into Male gametophyte and Megaspore develops into female gametophyte.<\/p>\n

Question 16.
\nWhat is meant by monosporic development of female gametophyte?
\nAnswer:
\nThe method of embryosac formation from a single Megaspore is called as Monosporic type of Embryo sac.<\/p>\n

Question 17.
\nMention two strategies evolved to prevent self-pollination in flowers.
\nAnswer:
\nHerkogamy and Heterostyly strategies evolved to prevent self-pollination in flowers.
\n1) Herkogamy :
\nThe anther and the stigma are placed at different positions so that anthers cannot come in contact with the stigma of the same flower.
\nEx : Hibiscus, Gloriosa<\/p>\n

2) Heterostyly :
\nStyles of the flowers of the same species are in different heights.
\nEx : Lythrum<\/p>\n

Question 18.
\nWhy do you think the zygote is dormant for some time in a fertilized ovule ?
\nAnswer:
\nIn a fertilised ovule, Endosperm develops before embryo development, the primary endosperm nucleus divides repeatedly and forms a triploid endosperm tissue. The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo. Thats why, the zygote is dormant for some time.<\/p>\n

Question 19.
\nIf one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?
\nAnswer:
\nBanana and Grapes are parthenocarpy fruits. These fruits are useful in juice and Jam industries because of more pulp.<\/p>\n

Question 20.
\nWhat is meant by scutellum? In Which type of seeds is it present?
\nAnswer:
\nThe single cotyledon of a monocot embryo is known as scutellum. It is situated towards one side of the embryonal axjs.
\nEx : Grass seeds.<\/p>\n

\"AP<\/p>\n

Question 21.
\nDefien with examples endospermic and non-endospermic seeds.
\nAnswer:<\/p>\n\n\n\n\n
Endospermic seeds<\/td>\nNon-endospermic seeds<\/td>\n<\/tr>\n
The mature seeds with endosperm are called as endospermic seeds.
\nEx : Castor and coconut.<\/td>\n		The mature seeds without endosperm are called as non-endospermic seeds.
\nEx : Pea, groundnut, beans.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Short Answer Type Questions<\/span><\/p>\n

Question 1.
\nList three strategies that a bisexual chasmogamous flower can evolve to prevent self pollinaltion (autogamy).
\nAnswer:
\nA) Dichogamy :
\n“Pollen release and stigma receptivity are not synchronised”. In sunflower, the pollen is released before the stigma becomes receptive (protandry). In Datura, Solanum, the stigma becomes receptive much before the release of pollen (Protogyny) leads to cross pollination.<\/p>\n

B) Herkogamy:
\nThe Male (anther) and female (stigma) sex organs are placed at different positions (Hibiscus) or in different directions (Gloriosa), called Herkogamy. In these plants, the pollen can not come in contact with the stigma of the same flower leads to cross pollination.<\/p>\n

C) Self-sterility :
\nIt is a genetic mechanism which prevents the self pollen from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
\nE.g. : Abutilon.<\/p>\n

Question 2.
\nGiven below are the events that are observed in an artifical hybridization programme. Arrange the in the correct sequential order in which they are followed in the hybridization programme.
\na) Re-bagging
\nb) Selection of parent
\nc) Bagging
\nd) Dusting the pollen on stigma
\ne) Emasculation
\nf) Collection of pollen from male.
\nAnswer:
\na) Selection of parents.
\nb) Emasculation
\nc) Bagging
\nd) Collection of pollen from male
\ne) Dusting the pollen on stigma
\nf) Re-bagging.<\/p>\n

Question 3.
\nWhat is polyembryony and how can it be commercially exploited?
\nAnswer:
\nOccurrence of more than one embryo in a seed is called polyembryony.<\/p>\n

In many citrus and Mango varieties, some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryosac and develop into embryos. In such species, each ovule contains many embryos.<\/p>\n

Polyembryony plays a main role in plant breeding and horticulture. The plantlets obtained from
\nthese embryos are virus free has more vigour.<\/p>\n

Hybrid varieties of several food and vegetable crops are being extensively cultivated. Cultivation of Hybrids has tremendously increased productivity.<\/p>\n

Question 4.
\nAre parthenocarpy and apomixis different phenomena? Discuss their benefits.
\nAnswer:
\nYes. Apomixis and parthenocarpy are different phenomenon.<\/p>\n

Significance of Apomixis :<\/p>\n

    \n
  1. During Apomixis, chromosomal seggregation and recombinations does not occur. So characters are stable for several generations.<\/li>\n
  2. It simplifies commercial Hybridised production because isolation would not be necessary to produce F, or maintain or Multiply parental generation.<\/li>\n
  3. Adventive embryony is being used in produced uniform root – Stock and virus free scion material.<\/li>\n<\/ol>\n

    Significance of parthenocarpy :<\/p>\n

      \n
    1. The fruit production without fertilization of the ovary is called parthenocarpy. This phenomenon is applied for the commercial production of seedless fruits.
      \nE.g. : Banana, Grapes.<\/li>\n
    2. This is more useful to juice industries. .<\/li>\n<\/ol>\n

      Question 5.
      \nWhy does the zygote begin to divide only after the division of Primary endosperm cell (PEC)?
      \nAnswer:
      \nThe primary endosperm cell divides repeatedly and forms a triploid endosperm tissue. The cells of this tissue are filled with reserve food materials and are used for nutrition of the developing embryo. Embryo develops at the Micropylar end of the embryosac where zygote is situated. Most zygotes divide only after certain amount of endosperm is formed. This is an adaptation to provide assured nutrition to the developing embryo.<\/p>\n

      Question 6.
      \nThe generative cell of two-celled pollen divides in the pollen tube but not in a three-celled pollen. Give reasons.
      \nAnswer:
      \nPollengrain, at maturity divides periclinally and produce two unequal cells. The larger cell is vegetative cell, has abundant food reserve and a large irregularly shaped nucleus. The smaller cell is generative cell and floats in the cytoplasm of vegetative cell which is spindle shaped with dense cytoplasm and a nucleus. In over 60% of angiosperms, pollengrains are shed at this 2\u2018celied stage. In the remaining, species, the generative cell divides mitotically to give rise to the 2 male gametes before pollen grains are shed (3 celled stage).<\/p>\n

      The pollen grain germinates on the stigma to produce a pollen tube through one of the germpores. The contents of the pollen grain moves into the pollen tube. Pollen tube grows through the tissues of the stigma and style and reaches the ovary.<\/p>\n

      In plants, when pollen grains are shed at 2 celled stage, the generative cell divides and forms two male gametes, during the growth of the pollen tube in the stigma.<\/p>\n

      \"AP<\/p>\n

      Question 7.
      \nDiscuss the various types of pollen tube entry into ovary with the help of diagrams.
      \nAnswer:
      \nPollen tube enters into the ovule by any one of the three ways.
      \n1) Porogamy :
      \nPollen tube enters into ovule through Micropyle and then enters into embryosac by destroying one of the synergids.
      \nE.g. : Ottelia, Hibiscus.<\/p>\n

      2) Chalazagamy :
      \nPollen tube enters into ovule through chalaza.
      \nE.g. : Casuarina.<\/p>\n

      3) Mesogamy :
      \nPollen tube enters into ovule through the integuments.
      \nE.g. : Cucurbita.
      \n\"AP<\/p>\n

      (a) Entry of Pollen tube through Micropyle
      \n(b) Entry of Pollen tube through Chalaza
      \n(c) Entry of Pollen tube through Integuments.<\/p>\n

      Question 9.
      \nDifferentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events.
      \nAnswer:<\/p>\n\n\n\n\n
      Microsporogenesis<\/td>\nMegasporogenesis<\/td>\n<\/tr>\n
      1. The sporogenous tissue divides Meiotically to form Microspore tetrads is called Microsporogenesis.<\/td>\n1. The process of formation of megaspores from the Megaspore Mother cell is called Megasporogenesis.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      In both these events Meiosis occurs. At the end of these events. Microspores and Megaspores are formed.<\/p>\n

      Question 10.
      \nWhat is bagging technique? How is it useful in a plant breeding programme?
      \nAnswer:
      \nCovering the emasculated flower with a bag made of butter paper is called Bagging.<\/p>\n

      In Artificial hybridisation technique, after the selection of parents, Anthers are to be removed from bisexual flower of a female parent is called Emasculation. After this, these emasculated flowers have to be covered with a bag of suitable size, generally made of butter paper. It is to be done to prevent contamination of the stigma with unwanted pollen. This process is called Bagging. Bagging technique is useful in producing new cultivar.<\/p>\n

      Question 11.
      \nWhat is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
      \nAnswer:
      \nFusion of second male gamete with secondary nucleus (fusion of product of two polar nuclei) is called Triple fusion.<\/p>\n

      It occurs in the embryosac. Pollen tube with two male gametes enters into embryosac by destroying one of the synergids.<\/p>\n

      The tip of the pollen tube dissolves and releases two male gametes in the vicinity of the egg. In tripple fusion, one male gamete and secondary nucleus (two polar nuclei) are involved.<\/p>\n

      Question 12.
      \nDifferentiate between
      \na) Hypocotyl and Epicotyl
      \nb) Coleoptile and Coleorhiza
      \nc) Integument and testa
      \nd) Perisperm and Pericarp.
      \nAnswer:
      \na)<\/p>\n\n\n\n\n\n
      Hypocotyl<\/td>\nEpicotyl<\/td>\n<\/tr>\n
      1. The cylindrical portion of embryonal axis below the level of cotyledons is called Hypocotyl.<\/td>\n1. The portion of embryonal axis above the level of cotyledons is called epicotyl.<\/td>\n<\/tr>\n
      2. It is smooth.<\/td>\n2. It is covered by tiny hairs.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      b)<\/p>\n\n\n\n\n
      Coleoptile<\/td>\nColeorhiza<\/td>\n<\/tr>\n
      The epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure called coleoptile.<\/td>\nThe embryonal axis has the radicle and root cap is enclosed in an undifferentiated sheath called coleorhiza.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      c)<\/p>\n\n\n\n\n
      Integument<\/td>\nTesta<\/td>\n<\/tr>\n
      Protective envelope around the ovule is called Integument.<\/td>\nAfter fertilization, the outer integument, of the ovule develops into Testa (outer seed coat).<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      d)<\/p>\n\n\n\n\n
      Perisperm<\/td>\nPericarp<\/td>\n<\/tr>\n
      Remmant of nucellus is called perisperm.
      \nEx : Black pepper.<\/td>\n      		The outer wall of a fruit is called pericarp.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      Question 13.
      \nWhat is meant by emasculation? When and why does a plant breeder employ this technique?
      \nAnswer:
      \n“Removal of Anthers from the bisexual flower of a female parent, when the flower is in Bud condition, with the help of a forceps” is called emasculation. This technique is employed, when only the desired pollengrains are used for pollination arid the stigma is protected from contamination.<\/p>\n

      \"AP<\/p>\n

      Question 14.
      \nWhat is apomixis? What is its importance?
      \nAnswer:
      \nProduction of seeds without fertilisation is called Apomixis. It is a form of asexual Reproduction that mimics sexual reproduction. In some species, the diploid egg cell is formed, with out Meiosis and develops into embryo without fertilization. It is an assured reproduction in the absence of pollinators such as in extreme environments.<\/p>\n

      Importance :<\/p>\n

        \n
      1. Apomixis do not involve meiosis. Hence reggregation and recombination of chromosomes do not occur. Thus Apomixis help in preserving desirable characters for Indefinite periods.<\/li>\n
      2. Apomixis, simplified commercial hybrid seed production.<\/li>\n<\/ol>\n

        Question 15.
        \nDescribe briefly different types of agents of pollination.
        \nAnswer:
        \nThe various agencies helpful in pollination can be grouped into two broad categories : biotic and abiotic. Majority of plants use biotic agents for pollination.<\/p>\n

        I. Abiotic pollinating agents :
        \nIt includes non-living agnets like air and water.
        \na) Anemophily :
        \nTransfer of pollen grains through wind is known as anemophily. It is the most common type of abiotic pollination method. Wind pollinated flowers are small, stigmas are feathery and non-sticky.
        \nEx : Widn pollination is a quite common in grasses.<\/p>\n

        b) Hydrophily :
        \nTransfer of pollen grains trhough the agnecy of water is known as hydrophily. It is of two types.<\/p>\n

        1) Hypohydrophily :
        \nIn this type the pollination of flowers occurs below the water level, it is found in submerged plants like Zosterra and sea grasses.<\/p>\n

        2) Epi-hydrophiiy :
        \nHere, the pollination of flower occurs at the surface of water.
        \nEx : Vallisneria and Hydrilla.<\/p>\n

        II. Biotic pollinating agents :
        \nIt includes living organisms such as insects, birds, bats and snail.
        \na) Entomophily :
        \nPollination thorugh the agncy of insects is known as entomophily.
        \nEx : Bees, beetles, wasps etc.<\/p>\n

        b) Ornithophily :
        \nPollination thorugh the agency of birds is kriown as ornithophily.
        \nEx : Sun birds and humming birds.<\/p>\n

        c) Cheiropterophily :
        \nPollination through the agency of bats is known as Cheiropterophily.<\/p>\n

        d) Therophily :
        \nPollination through the agency of squirrels is known as Therophily.<\/p>\n

        e) Ophiophily :
        \nPollination through the agency of snakes is known as ophiophily.<\/p>\n

        Question 16.
        \nWrite briefly about the different types of ovules.
        \nAnswer:
        \nThe ovule is a megasporangium with one or two integuments. In Angiosperms three main types of ovules are present. They are :<\/p>\n

        1) Orthotropous ovule :
        \nIt is traight ovule with micropyle, chalaza and funiculus arranged in one stright line. It is a primitive type of ovule.
        \nEx : Polygonum, Piperaceae.<\/p>\n

        2) Anatropous ovule :
        \nIt is a inverted type of ovule. Due to unilateral growth of funicle, the whole body of the ovule is inverted through 180\u00b0. As a result the micropyle comes close to the base of the funicle. The most common type of ovule found in several families.
        \nEx : Healianthus, Tridax.<\/p>\n

        3) Campylotropous ovule : In this type of body of the ovule is bent more or less at right angles to the funicle. The microphyle part of the ovule become curved, without any curvature in the embryosac.
        \nEx : Fabaceae, Brasicaceae.
        \n\"AP<\/p>\n

        Question 17.
        \nVivipary automatically limits the number of offsprings in a litter. How?
        \nAnswer:
        \nVivipary is defined as the seeds germinate while they are still attached to the mother plant. Plants which grows in Marshy places are called Mangrooves. In these plants, seeds when fall on Marshy places, can not germinate because of high salinity and more water conditions. So in those plants, seeds germinate when they are in mother plant to raise their generations. The seeds of Mangrooves can not germinate even on litter because of unfavourable conditions. So the number of offsprings will dicrease.<\/p>\n

        Question 18.
        \nDoes self incompatibility impose any restrictions on autogamy? Give reasons and suggest the method of pollination in such plants.
        \nAnswer:
        \nSelf Sterility :
        \nIn some bisexual flowers, if the pollengrains fall on the stigma of the same flower, germination does not occur. But the same pollen grains germinates when they fall on the stigma of other flowers of the same species. It is a genetic mechanism to prevent self pollination.
        \nE.g. : Abutilon, Passiflora. In these plants cross pollination only occurs. In some plants, the pollen grains become poisonous and make the flower wither if self pollination occurs. E.g. : Orchids.<\/p>\n

        Question 19.
        \nExplain the role of tapetum in the formation of pollen grain wall.
        \nAnswer:
        \nThe inner walls of Tapetal layer breaks and releases their protoplasts into the inner space of the Anther. There, they mix with each other and form periplasmodium. It covers the Microspore Mother cells, help in the formation of outer wall (exine) of pollen grain. Moreover, the ubisch bodies of Tapetum chemically made of carotenes and carotenoids which are equallent to sporopollenin of pollengrain.<\/p>\n

        Long Answer type Questions<\/span><\/p>\n

        Question 1.
        \nStarting with the zygote, draw the diagrams of the different stages of embryo development in a dicot.
        \nAnswer:
        \n\"AP<\/p>\n

        Question 2.
        \nWhat are the possible types of pollinations in chasmogamous flowers? Give reasons.
        \nAnswer:
        \nChasmogamy :
        \nThe pollination that occurs in opened flowers is called chasmogamy. It is the most common type of pollination in all types of flowers. There are two types of chasmagamy.<\/p>\n

          \n
        1. Self pollination<\/li>\n
        2. Cross pollination.<\/li>\n<\/ol>\n

          1) Self Pollination :
          \nThe transfer of pollengrians from Anther to stigma of the same flower is called autogamy or self-pollination. It is found in both cleistogamous and chasmogamous flowers.<\/p>\n

          2) Cross pollination Or allogamy :
          \nThe transfer of pollengrains from Anther to stigma of another flower is called cross pollination. It is of 2 types,
          \na) Geitonogamy
          \nb) Xenogamy.<\/p>\n

          a) Geitonogamy :
          \nThe transfer of pollengrains from anther to the stigma of another flower of the same plant. It is functionally Gross pollination involving a pollinating agent, genetically, it is similar to autogamy. Since the pollengrains come from the same plant.<\/p>\n

          b) Xenogamy :
          \nThe transfer of pollengrains from the flower of one plant to the stigma of another plant. This is the only type of pollination which brings genetically different types of pollengrains to the stigma.<\/p>\n

          Question 3.
          \nWith a neat, labelled diagram, describe the parts of a mature angiosperm embryo sac. Mention the role of synergids.
          \nAnswer:
          \nMegaspore is the Mothercell for the development of female gametophyte (embryosac). The nucleus of the functional Megaspore divides mitotically to form two nuclei, which move to the opposite poles forming 2 nucleate embryo sac. Two more Mitotic nuclear divisions occur in two nuclei results the formation of 8 nucleate embrayo sac. After this stage, cell walls are laid down leading to the organization of the typical femaie gametophyte or embryo sac.<\/p>\n

          Six of the eight nuclei are surrounded by cell walls and organised into cells. Three cells present towards the micropylar end grouped together, constitute the egg apparatus. The egg apparatus, inturn consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filliform apparatus which play an importent role in guiding the pollen tubes into the synergid.<\/p>\n

          Three cells of the chalazal end are called the antipodals. The large central cell is formed by the fusion of 2 polar nuclei. Thus a typical angiospermic embryosac, at maturity consists of 8 nuclei and 7 cells. This embryosac is formed from the single megaspore, so called Monosporic embryo sac.<\/p>\n

          Role of synergids :
          \nFiliform apparatus in synergids help in guiding the pollen tubes towards the embryo sac.
          \n\"AP
          \n(a) Parts of the ovule showing a large megaspore mother cell, a dyad and a tetrad of megaspores.
          \n(b) 2, 4 and 8-nucleate stages of embryo sac and a mature embryo sac.
          \n(c) A diagrammatic representation of the mature embryo sac.<\/p>\n

          \"AP<\/p>\n

          Question 4.
          \nDraw the diagram of a microsporangium and label is wall layers. Write briefly about the wall layers.
          \nAnswer:
          \n\"AP
          \n(a) Transverse section of a young anther
          \n(b) Enlarged view of one microsporangium showing wall layersl<\/p>\n

          A typical angiospermic anther is bilobed with each lobe having two theca. The anther is a four sided structure consisting of four microsporangia located at the corners, two in each lobe.<\/p>\n

          In a transverse section, a typical microsporangium is circular in out line and is surrounded by four wall layers, the
          \na) epidermis
          \nb) endothecium
          \nc) wall layers
          \nd) tapetum.<\/p>\n

          a) Epidermis :
          \nThe epidermis is one called thick, the cells present between the pollen sacs are the thin walled and their region is called as stomium which is useful for the dehiscence of pollen sacs.<\/p>\n

          b) Endothecium :
          \nIt is present below the epidermis and expands radically with fibrous thickenings, at maturity these cells loose water and contract and help in the dehiscence of pollen sacs.<\/p>\n

          c) Wall layers :
          \nBeneath the Endothecium, there are thin walled cells, arranged in one to five layers, which also help in dehiscence of Anther.<\/p>\n

          d) Tapetum :
          \nThe innermost wall layer is Tapetum, the cells are large, with thin cell walls, abundant cytoplasm and have more than one nuclei. Tapetum is a nutritive tissue which nourishes the developing pollen grains.<\/p>\n

          The centre of the microsporengium consists of sporogeneous tissue, which undergo meiotio divisions to form microspore tetrads. This process is known as Microsporogenesis.<\/p>\n

          Question 5.
          \nEmbryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.
          \nAnswer:
          \nReplacement of the normal sexual reproduction by asexual reproduction without fertilisation is called apomixis. It does not mention Meiosis. Replacement of the seed by a plant, or replacement of the flower by bulbils are types of apomixis. Apomitically produced offsprings are genetically identical to the parent plant. In flowering plants, apomixis is used in a restricted sense to mean aganosperms i.e., asexual reproduction through seeds. In some plant families, apomixis is common.
          \nEx : Astha ceae, Poaceae.<\/p>\n

          In some species, the diploid egg cell is formed without reduction division and develops into embryo without fertilisation. It is an asexual reproduction in the absence of pollinators such as in extreme environments. In some species like citrus, some of the nuclear cells surrounding the embryosac start dividing and develop into embryos.<\/p>\n

          In Allium, Antenraria, the megaspore mother cell does not enter Meiosis and produces diploid embryosac through Mitotic divisions.<\/p>\n

          In Hieracium species, the Megaspore mother cell undergoes meiosis to form a letraol. At this stage, the nucellar cell at the chalazal end becomes activated and starts developing into aposposons unreduced embryosac which only matures.<\/p>\n

          Importance :
          \nApomixis do not involve meiosis. Hence segregation and recombination of chromosomes do not occur. It helps in the pereserving desirable characters for Indefinite periods.<\/p>\n

          Finally it states that, Embryosacs of some opomitic species appear normal but produce diploid cells.<\/p>\n

          \"AP<\/p>\n

          Question 6.
          \nDescribe the process of Fertilization in angiosperms.
          \nAnswer:
          \nFusion of male and female gametes is called Fertilization. In Angiosperms, Female gamete (Egg) is embeded in ovule. Pollengrians are carried upto stigma by some agents, germinate and produce pollentubes. They enter into ovule and releases male gametes near the Egg in Embryo sac.<\/p>\n

          In Angiosperms, Fertilization completes in 5 steps they are
          \nA) Entry of pollentube into the ovule : Pollentube enter into the ovule by any one of three ways. They are
          \n1) Porogamy :
          \nPollentube enters into the ovule through micropyle and then into embryo sac by destroying one of the svnergids.
          \nEx : Ottelia, Hibiscus<\/p>\n

          2) Chalazogermy :
          \nPollentube enters in to theo vule through chalaza.
          \nEx : Casuarina<\/p>\n

          3) Mesogamy :
          \npollentube enters into the ovule through the integuments.
          \nEx : Cucurbita,
          \n\"AP
          \n(a) Entry of Pollen tube through Micropyle
          \n(b) Entry of Pollen tube through Chalaza
          \n(c) Entry of Pollen tube through Integuments.<\/p>\n

          B) Entry of pollentube into the embryo sac :
          \nAfter entering into the ovule by anyone of the three methods, pollentube enter into the embryosac by destroying one of the synergids or by space present between the Egg and synergids. Filliform apparatus in synergids helps in entering into the embryo sac.<\/p>\n

          C) Discharge of Male gametes :
          \nDue to the dissolution of the tip of the pollentube or by pore formed at the tip of the pollentube, two male gametes are released near the Egg in embryo sac.<\/p>\n

          D) Syngamy :
          \nOne male gamete fuses with the Egg forming diploid zysote. It was discovered by strasberger in 1884.<\/p>\n

          E) Triple Fusion :
          \nSecond male gamete fuses with the secondary nucleus forming triploid primary endosperm nucleus. In this, one haploid male gamete fuses with diploid secondary nucleus forming Triploid primary endosperm nucleus. So called Triple fusion. It was first discovered by Nawaschin in hilium and fertilillaria.<\/p>\n","protected":false},"excerpt":{"rendered":"

          Andhra Pradesh BIEAP AP Inter 1st Year Botany Study Material 7th Lesson Sexual Reproduction in Flowering Plants Textbook Questions and Answers. AP Inter 1st Year Botany Study Material 7th Lesson Sexual Reproduction in Flowering Plants Very Short Answer Questions Question 1. Name the component cells of the “egg apparatus” in an embryo sac. Answer: One …<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[15],"tags":[],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/posts\/35717"}],"collection":[{"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/comments?post=35717"}],"version-history":[{"count":1,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/posts\/35717\/revisions"}],"predecessor-version":[{"id":35718,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/posts\/35717\/revisions\/35718"}],"wp:attachment":[{"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/media?parent=35717"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/categories?post=35717"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/apboardsolutions.guru\/wp-json\/wp\/v2\/tags?post=35717"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}