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23 09 2019 Microsporogenesis

This document describes the sexual reproduction process in flowering plants. It discusses the male and female structures - the stamen and pistil. The stamen contains the anther and filament, which produce and support pollen grains. The pistil contains the stigma, style and ovule. Pollen grains contain vegetative and generative cells and are produced through microsporogenesis within the anther. Pollen lands on the stigma and can fertilize the ovule, leading to seed formation. Accessory structures like petals and sepals also support the reproductive process.

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Shalini Jha
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214 views23 pages

23 09 2019 Microsporogenesis

This document describes the sexual reproduction process in flowering plants. It discusses the male and female structures - the stamen and pistil. The stamen contains the anther and filament, which produce and support pollen grains. The pistil contains the stigma, style and ovule. Pollen grains contain vegetative and generative cells and are produced through microsporogenesis within the anther. Pollen lands on the stigma and can fertilize the ovule, leading to seed formation. Accessory structures like petals and sepals also support the reproductive process.

Uploaded by

Shalini Jha
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Sexual Reproduction In Flowering Plants
● All flowering plants
(angiosperms) show sexual
reproduction.
● Flowers are the sites of
sexual reproduction
Structure of Flower
Stamen
Stamen
The male part of the flower is called
the stamen and is composed of:
● Anther – pollen producing organ
of the flower (pollen is the male
gamete of a flowering plant)
● Filament – slender stalk
supporting the anther (makes the
anther accessible to pollinators)
Pistil or Carpel
Pistil or Carpel
The female part of the flower is called the pistil (or
carpel) and is composed of:
● Stigma – the sticky, receptive tip of the pistil
that is responsible for catching the pollen
● Style – the tube-shaped connection between
the stigma and ovule (it elevates the stigma to
help catch pollen)
● Ovule – the structure that contains the female
reproductive cells (after fertilisation, it will
develop into a seed)
Accessory Organ
In addition to these reproductive
structures, flowers possess a number of
other support structures:
● Petals – brightly coloured modified
leaves, which function to attract
pollinators
● Sepal – Outer covering which
protects the flower when in bud
● Peduncle – Stalk of the flower
PRE-FERTILISATION:
● Anther: Terminal and typically bilobed, each
lobe has two thecae (dithecous).
● It is tetragonal structure consisting of four
microsporangia located at the corners.
● Each lobe consists of two microsporangia.
● Microsporangia develops into pollen sac.
THECAE

Dithecous
Sporogenous tissue
Microsporogenesis
Structure of microsporangium
● Microsporangium is surrounded by four wall
layers the epidermis, endothecium, middle
layers and the tapetum.
● The outer three wall layers - protects and help in
dehiscence of anther
● Tapetum (innermost wall layer) nourishes the
developing pollen grains.
● Cells of the tapetum possess dense cytoplasm
and generally have more than one nucleus
Microsporogenesis
● Sporogenous tissue undergo meiotic divisions
to form microspore tetrads (microspores are
arranged in a cluster of four cells).
● Each one is a potential pollen (microspore
mother cell).
● The process of formation of microspores from
a pollen mother cell through meiosis is called
microsporogenesis.
● Microspore develop into pollen grains
Pollen Grain

Sporopollenin
Pollen Grain
● Pollen grains represent the male gametophytes.
● Pollen grains are of 25-50 micrometers in diameter.
● Exine: wall. The hard outer layer made up of sporopollenin (the most
resistant organic material)
● Germ pores prominent apertures of pollen grain called where
sporopollenin is absent
● Intine: The inner wall of the pollen grain it is a thin and made up of
cellulose and pectin.
● Mature Pollen grain contains two cells, the vegetative cell and
generative cell.
Pollen Grains
● Vegetative cell- bigger, abundant food reserve and a large irregularly shaped nucleus.
● Generative cell -small and spindle shaped with dense cytoplasm and a nucleus.
● Pollen grains are shed at 2-celled stage or 3-celled stage
Pollen Grains
● Pollen grains of many species cause severe
allergies and leading to chronic respiratory
● Disorders– asthma, bronchitis, etc.
● Pollen grains are rich in nutrients.
● Pollen tablets and syrups are used as food
supplements.
● It increase the performance of athletes and
race horses.
● Pollen grains can be stored for years in liquid
nitrogen (-1960C).

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