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 (B)</p> Signup and view all the answers

Which structure in the pistil receives pollen grains?

<p>Stigma (C)</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 (B)</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 (B)</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 (B)</p> Signup and view all the answers

Where are germ pores found in pollen grains?

<p>In areas devoid of exine (D)</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 (B)</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 (A)</p> Signup and view all the answers

What is the study of pollen called?

<p>Palynology (A)</p> Signup and view all the answers

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

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

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

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

What is the function of pollen creams?

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

The funiculus connects which two structures in the ovule?

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

What characteristics define the endothecium layer of the anther?

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

What occurs during microsporogenesis?

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

How are tetrads classified during microsporogenesis?

<p>Into five distinct types, including tetrahedral and linear. (D)</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. (C)</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. (A)</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. (A)</p> Signup and view all the answers

What happens to the anther when it matures?

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

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

<p>Caruncle (A)</p> Signup and view all the answers

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

<p>Four (B)</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 (C)</p> Signup and view all the answers

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

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

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

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

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

<p>They degenerate (B)</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 (A)</p> Signup and view all the answers

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

<p>Cuticle (C)</p> Signup and view all the answers

What is self-pollination primarily characterized by?

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

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

<p>Xenogamy (D)</p> Signup and view all the answers

What is one disadvantage of self-pollination?

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

What defines protandry in pollination?

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

Which of the following is an adaptation for autogamy?

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

What is the main benefit of self-pollination?

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

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

<p>Dimorphic heterostyly (B)</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. (C)</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. (D)</p> Signup and view all the answers

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

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

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

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

Flashcards

Endothecium

The single-layered wall beneath the epidermis of an anther, thickened with cellulose, pectin, and lignin. It helps the anther open.

Microsporogenesis

The process of microspore formation and differentiation in plants.

Tapetum

The innermost layer of the anther wall surrounding sporogenous tissue; provides nutrients to developing microspores.

Pollen grain development

The formation and maturation of pollen grains, including the formation of a two-layered wall (exine and intine) around microspores.

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Microspore mother cell

The diploid cell that undergoes meiosis to produce microspores

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Tetrahedral tetrad

A common arrangement of four microspores formed after meiosis, arranged in a tetrahedron shape.

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Anther dehiscence

The splitting open of the anther to release pollen.

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Exine and intine

The two-layered wall of a pollen grain; the outer wall is the exine and the inner wall is the intine.

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Pollinium

A mass of pollen grains found on an anther lobe of some flowers.

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Pollen Grain Structure

Has a two-layered exterior wall (sporoderm): the outer exine and the inner intine.

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Exine

Outer layer of the pollen grain wall, made of sporopollenin.

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Intine

Inner layer of the pollen grain wall, made of pecto-cellulose.

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Germ Pores/Furrows

Openings in the exine through which the pollen tube emerges.

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Pollen Grain Classification

Based on the number of germ pores (e.g., monocpate, biclopate).

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Palynology

The study of pollen.

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Male Gametophyte Development

Inside the pollen grain, the nucleus divides to form a vegetative and a generative cell.

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Pollen Viability

The length of time that pollen grains remain functional. It's influenced by temperature and humidity.

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Pollen Supplements

Pollen grains are rich in carbohydrates and unsaturated fats. They are consumed in tablets and syrups to enhance bodily functions and performance.

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Pollen Creams

Pollen grains offer UV protection and are used in creams and lotions for skin smoothness and protection.

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Pollen Allergy

Pollen grains cause severe allergies, including respiratory disorders like asthma and bronchitis.

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Stigma

The part of the pistil that receives pollen grains. It's the top part of the female reproductive unit.

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Style

The stalk that connects the stigma to the ovary in the pistil.

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Ovary

The swollen base of the pistil containing one or more ovules. It develops into a fruit after fertilization.

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Ovule

A megasporangium surrounded by integuments, located within the ovary. It develops into a seed after fertilization.

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Chalazal End

The point where the integuments of an ovule are attached to the funiculus (stalk) of the ovule.

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Micropyle

A tiny opening in the integuments of an ovule, located at the opposite end from the chalazal end, allowing the pollen tube to enter.

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Caruncle

A fleshy appendage found at the micropylar end of some seeds, formed by the proliferation of integumentary cells.

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Megasporogenesis

The process of formation of megaspores from the megaspore mother cell (MMC) within the ovule.

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Functional Megaspore

The single megaspore out of four produced by meiosis, which develops into the embryo sac.

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Monosporic Development

The formation of an embryo sac from a single functional megaspore, characteristic of most flowering plants.

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Egg Apparatus

A group of three cells at the micropylar end of the embryo sac, consisting of two synergids and one egg cell.

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Pollination

The transfer of pollen grains from the anther to the stigma of a flower.

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Self-Pollination

Transfer of pollen grains from anthers to stigmas of the same or different flowers on the same plant.

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Autogamy

Self-pollination within the same flower.

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Cleistogamy

Self-pollination in closed flowers that never open.

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Geitonogamy

Transfer of pollen from one flower to another on the same plant, but not within the same flower.

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Cross-Pollination

Transfer of pollen grains from the anther of one plant to the stigma of another plant of the same or different species.

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Dichogamy

Maturation of anthers and stigmas at different times in the same flower.

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Xenogamy

Cross-pollination between genetically and ecologically distinct plants of the same species.

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Self-Sterility

A plant's inability to self-fertilize due to pollen grains being incapable of growing on the stigma of the same flower.

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Prepotency

The ability of a pollen grain to grow faster on the stigma of another plant than on the stigma of the same plant.

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Heterostyly

A mechanism where styles and stamens are at different heights within flowers to prevent self-pollination.

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Pin-Eye & Thrum-Eye

Two types of flowers in dimorphic heterostyly, distinguished by the position of the style and stamen. Pin-eye has a long style and short stamen, while thrum-eye has a short style and long stamen.

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Advantages of Cross-Pollination

Cross-pollination leads to genetic variation, improved adaptation to environmental changes, and elimination of defective traits.

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Disadvantages of Cross-Pollination

Cross-pollination may require a large number of pollen grains, can spoil good traits, and involves an element of chance.

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Significance of Pollination

Pollination is essential for fertilization, seed and fruit production, ovarian growth, and the creation of hybrid seeds.

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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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Class 12 Chapter 1 Sexual Reproduction In Flowering Plants Notes PDF

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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