Sexual Reproduction in Flowering Plants
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Questions and Answers

What structure is responsible for the identification and classification of pollen grains?

  • Tectum (correct)
  • Germ pores
  • Intine
  • Exine
  • Which component of the pollen grain is resistant to chemical and biological decomposition?

  • Cellulose
  • Pecto-cellulose
  • Intine
  • Sporopollenin (correct)
  • What is the binomial classification of pollen grains based on germ pores?

  • Monoclopate, Biclopate, Triclopate (correct)
  • Biclopate, Tricarpate, Monocarpate
  • Monocarpate, Biclopate, Quadrilopate
  • Monoclopate, Triclopate, Quadrilopate
  • What is the functional role of the vegetative cell in a pollen grain?

    <p>To form the pollen tube</p> Signup and view all the answers

    Which structure in the pistil receives pollen grains?

    <p>Stigma</p> Signup and view all the answers

    Which of the following describes the structure of the intine in the pollen grain?

    <p>Thin and pliable</p> Signup and view all the answers

    What is the first developmental stage of the male gametophyte within the pollen grain?

    <p>Division of nucleus</p> Signup and view all the answers

    What type of cells form male gametes in the pollen grain while still within the anther?

    <p>Generative cells</p> Signup and view all the answers

    Where are germ pores found in pollen grains?

    <p>In areas devoid of exine</p> Signup and view all the answers

    What happens to the generative cell after pollen has landed on the stigma when it is shed at the two-celled stage?

    <p>It divides after landing</p> Signup and view all the answers

    Which of the following contributes to the composition of the vegetative cell's cytoplasm?

    <p>Fat, carbohydrate, and protein granules</p> Signup and view all the answers

    What is the study of pollen called?

    <p>Palynology</p> Signup and view all the answers

    What is the duration of pollen viability in terms of time?

    <p>30 minutes</p> Signup and view all the answers

    Which allergen is identified as a significant source of pollen allergies in India?

    <p>Carrot grass</p> Signup and view all the answers

    What is the function of pollen creams?

    <p>Providing UV protection</p> Signup and view all the answers

    The funiculus connects which two structures in the ovule?

    <p>Ovule and placenta</p> Signup and view all the answers

    What characteristics define the endothecium layer of the anther?

    <p>It aids in the dehiscence of anthers.</p> Signup and view all the answers

    Which of the following describes the structure of the tapetum?

    <p>It consists of secretary and amoeboid types.</p> Signup and view all the answers

    What occurs during microsporogenesis?

    <p>Each microspore mother cell undergoes meiosis.</p> Signup and view all the answers

    How are tetrads classified during microsporogenesis?

    <p>Into five distinct types, including tetrahedral and linear.</p> Signup and view all the answers

    What is the function of the outer wall, known as the exine, in pollen grains?

    <p>It protects the inner pollen from dehydration.</p> Signup and view all the answers

    What is true about the arrangement of nuclei in a tetrad after meiosis?

    <p>All nuclei in a tetrad remain functional.</p> Signup and view all the answers

    Which type of cytokinesis occurs in some microspores during tetrad formation?

    <p>Sequential cytokinesis occurs after each nuclear division.</p> Signup and view all the answers

    What happens to the anther when it matures?

    <p>The tapetum depletes and the anther dries out.</p> Signup and view all the answers

    What structure develops from the integumentary cells in the castor bean at the microplylar region?

    <p>Caruncle</p> Signup and view all the answers

    How many megaspores are produced from one megaspore mother cell during megasporogenesis?

    <p>Four</p> Signup and view all the answers

    Which stage follows the formation of a two-nucleate embryo sac during embryo sac development?

    <p>Four-nucleate stage</p> Signup and view all the answers

    Which cells are found at the micropylar end of the embryo sac?

    <p>Egg apparatus</p> Signup and view all the answers

    What is the role of the filiform apparatus found in the synergids?

    <p>Guides pollen tubes</p> Signup and view all the answers

    What typically occurs to the three megaspores that do not become the functional megaspore?

    <p>They degenerate</p> Signup and view all the answers

    How many cells and nuclei are present in a typical angiosperm embryo sac at maturity?

    <p>7 cells and 8 nuclei</p> Signup and view all the answers

    Which part of the integument serves as the outer protective layer?

    <p>Cuticle</p> Signup and view all the answers

    What is self-pollination primarily characterized by?

    <p>Transfer of pollen grains within the same plant.</p> Signup and view all the answers

    Which of the following is NOT a type of self-pollination?

    <p>Xenogamy</p> Signup and view all the answers

    What is one disadvantage of self-pollination?

    <p>Reduction in vitality over generations.</p> Signup and view all the answers

    Which of the following correctly defines cross-pollination?

    <p>Transfer of pollen grains from one plant to another.</p> Signup and view all the answers

    What is dicliny in terms of pollination?

    <p>The presence of only male or only female flowers on a plant.</p> Signup and view all the answers

    What defines protandry in pollination?

    <p>Anthers mature at a faster rate than stigmas.</p> Signup and view all the answers

    Which of the following is an adaptation for autogamy?

    <p>Flowers exhibit a closed structure.</p> Signup and view all the answers

    What is the main benefit of self-pollination?

    <p>Preserves genetic purity of the plant race.</p> Signup and view all the answers

    Which of the following best describes self-sterility in plants?

    <p>Pollen grains cannot grow over the stigma of the same flower.</p> Signup and view all the answers

    What does prepotency refer to in plant reproduction?

    <p>Pollen grains growing faster on the stigma of another plant.</p> Signup and view all the answers

    In which type of heterostyly do plants have two distinct types of flowers?

    <p>Dimorphic heterostyly</p> Signup and view all the answers

    What is the main advantage of cross-pollination in plants?

    <p>It promotes genetic recombination and variation in offspring.</p> Signup and view all the answers

    What is the role of the germ tube after pollen grains land on the stigma?

    <p>It secretes enzymes that digest stigma tissues.</p> Signup and view all the answers

    What defines porogamy in the context of pollen tube entry into ovules?

    <p>Entry through a micropyle.</p> Signup and view all the answers

    Which of the following is NOT a disadvantage of cross-pollination?

    <p>It is entirely self-sufficient.</p> Signup and view all the answers

    What occurs immediately after pollination in the pollen grain?

    <p>The nucleus divides to form vegetative and generative cells.</p> Signup and view all the answers

    Study Notes

    Sexual Reproduction in Flowering Plants

    • Sexual reproduction involves the fusion of male and female gametes from two parents.
    • Flowers are the primary reproductive structures in flowering plants.
    • Sporophylls are the reproductive organs within the flowers, classified into:
    • Microsporophylls (stamens)
    • Megasporophylls (carpels)
    • A carpel contains:
    • Ovule
    • Style
    • Stigma
    • Stamens consist of:
    • Filament
    • Anther
    • Connective
    • Sexual reproduction in flowering plants has three steps:
    • Pre-fertilization
    • Double fertilization
    • Post-fertilization

    Pre-Fertilization: Structure and Events

    • Pollen grain formation
    • Embryo sac formation

    Pollen Grain Formation

    • Stamen: The male reproductive unit, composed of an anther and a filament.
    • Anther: Bilobed, with each lobe containing four pollen sacs (microsporangia).
    • Pollen sacs contain numerous pollen grains.
    • Anther wall: Composed of four layers of cells.
    • Anther dehiscence: Release of pollen grains through slits.
    • Anther development: Begins with homogeneous meristematic cells, forming four lobes and four layers of archesporial cells.
    • Archesporial cells: Divide to form primary parietal cells and primary sporogenous cells.
    • Parietal cells: Form the anther wall.
    • Sporogenous cells: Form microspores or pollen mother cells (PMCs).
    • Tapetum: Innermost wall layer that feeds the growing spores.
    • Microspores development (Microsporogenesis):
    • PMCs undergo meiosis, forming tetrahedral tetrads.
    • Cytokinesis: Sequential or simultaneous.
    • Tetrads: Classified into five types (tetrahedral, isobilateral, decussate, T-shaped, linear).
    • Cell wall formation after meiosis I and II.
    • Pollen grains: Male gametophyte's first cells
    • Anther dehiscence: Pollen liberation
    • Pollen grains: Vary in shape and size. Typically 25-30 micrometers in diameter. Have a double-layered exterior wall (sporoderm):
    • Exine: Outer layer, thick, sporopollenin-composed.
    • Intine: Inner layer, thin, composed of pectin and cellulose.
    • Microspores: Present as pollinium in some families (Asclepiadaceae and Orchidaceae).

    Pollen Viability

    • Pollen viability: Time pollen grains remain functional; estimated by temperature and humidity.
    • Pollen grains are viable for 30 minutes.

    Pollen Allergy

    • Pollen grains cause various respiratory disorders (asthma, bronchitis), allergies.
    • Carrot grass is a significant allergen.

    Female Reproductive Unit (Pistil)

    • The female reproductive unit is the pistil (gynoecium).
    • Pistil/carpel: Composed of stigma, style, and ovary.
    • Stigma: Part that receives pollen grains.
    • Style: Connects stigma to the ovary.
    • Ovary: Swollen base containing one or more ovules (megasporangium surrounded by integuments).
    • Ovule develops into a seed after fertilization
    • Funiculus: Stalk that attaches ovule to placenta.
    • Hilum: Point where funicle attaches to the ovule.
    • Nucellus: Parenchymatous tissue equivalent to the megasporangium.
    • Micropyle: Pore at the opposite end of the integuments from the chalaza.
    • integuments: layers surrounding the nucellus.
    • Endothelium may nourish the developing embryo sac.
    • Cuticle: Layer covering the integuments and nucellus.

    Megasporogenesis

    • Megasporogenesis: Process of producing megaspores from the megaspore mother cell (MMC).
    • MMC is located in the nucellar micropylar region of the ovule.
    • MMC undergoes meiosis, producing four megaspores.
    • In most flowering plants, only one megaspore survives, developing into the female gametophyte (embryo sac).

    Embryo Sac Formation

    • Mitosis in the functional megaspore forms a two-nucleate embryo sac.
    • Subsequent mitotic divisions result in a four-nucleate, then eight-nucleate embryo sac.
    • Cell walls develop after the eight-nucleate stage, establishing a multicellular structure (female gametophyte).
    • Embryo sac: Contains cells like the egg apparatus (egg cell + synergids), central cell (two polar nuclei), and antipodal cells.

    Double Fertilization

    • Fusion of two male gametes with different structures within the embryo sac.
    • One sperm fertilizes the egg cell, forming the zygote (2n).
    • The other sperm fuses with the two polar nuclei, forming the triploid primary endosperm nucleus (3n).
    • Results in the formation of the diploid zygote and the triploid endosperm.

    Post Fertilization

    • Endosperm: Nutritive tissue resulting from the triple fusion (3n) that nourishes the embryo.
    • Endosperm development follows a variety of patterns.
    • It may be either cellular or nuclear or a combination both.
    • Endosperm nourishes the developing embryo and seedlings.

    Importance of Seeds

    • Evolutionary success: Encloses the embryo to prevent harm and provide food reserves.
    • Seed dispersal: Colonization and propagation to new areas.
    • Genetic variation: Adaptability to diverse environments.
    • Agriculture and civilization: Crucial for food production and human development.

    Seed Viability

    • The period during which seeds retain the ability to germinate.
    • Affected by genetic and environmental factors (humidity, temperature).
    • Viability may last from a few days to over a century.

    Apomixis

    • Asexual reproduction that mimics sexual reproduction in seed plants, forming seeds without fertilization.
    • Controlled by genes, resulting in genetically identical offspring (clones).

    Polyembryony

    • Presence of more than one embryo in a seed.
    • May be true polyembryony (fertilization of more than one egg) or false polyembryony (embryos formed from parts of the ovule other than the egg).
    • Examples: Citrus, groundnut.

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    Description

    This quiz covers the key concepts of sexual reproduction in flowering plants, focusing on the structures and events involved, including the reproductive organs, fertilization processes, and pollen grain formation. Test your knowledge on the roles of male and female gametes and the intricacies of flowers in plant reproduction.

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