SEXUAL REPRODUCTIO
Flowering Plants
Much b
All flowering plants INTRODUCTION actual flow
a plant, the
show sexual the plant
flower has
reproduction.
Several ho
structura
Flowers are objects differentia
the floral p
of aesthetic, ornamental,
which
I
social, religious and infloresce
S
cultural value. They have floral bud
Y
always been used as the f
H
symbols for conveying
P
important human
feelings such as love,
L L
affection, happiness,
A
grief, mourning etc.
W
PRE-FERTILISATION-STRUCTURES AND EV
Stamen, Microsporangium and Pollen Grain
Androecium, consists of a whorl of stamens, representing the male repro
A typical Stamen has two parts
Filament A
• It is long slender stalk. • The terminal part
• The proximal end of the filament is attached • Each lobe having
, MICROSPOROGENESIS
Microsporogenesis is a process of formation of microspores from PMC (Pol
As the anther Cells of the Undergoes
develop sporogenous
tissue(PMC) MEIOSIS
Each cell of the sporogenous tissue is a potential pollen The microspores, as they are formed, are arranged in a As
or microspore mother cell. cluster of four cells - the microspore tetrad. di
Sporopollenin is one of most resistant organic material known. It can withstand high temperature, strong acid
it is known. Pollen grains are well preserved as fossil due to it.
POLLEN GRAIN
Pollen grains represent the male gametophytes. A variety of architecture-sizes, shapes, colours, designs are see
Exine
• Outer hard layer
Vegetative cell
I
• Has germ pores
S
Bigger, has abundant
food reserve & a large
Y
irregularly shaped nucleus
P H
Generative cell
Small, floats in the cytoplasm of
Intine
vegetative cell; spindle shaped with
L
dense cytoplasm and a nucleus
Inner wall layer, thin con
A L
Pollen grains are generally spherical; measuring 25-50 micrometers in diameter
W
In over 60 % of angiosperms, pollen grains are shed at 2-celled stage, in the remaining species, generative cell divides mitotically to give rise to
(3-celled Generative cell divides mitotically and form two non motile ame gametes).
Pollen grains of many species cause severe allergies, chronic respiratory disorders, asthma, bronchitis etc e.g., Parthenium (carrot grass) came
became ubiquitous in occurrence & causes pollen allergy.
Pollen grains are rich in nutrients. Pollen tablets and syrups has been claimed to increase performance of athletes & race horses.
Pollen Viability: Highly variable. Depends to some extent on prevailing temperature and humidity.
In some cereals like rice and wheat pollen grains lose viability within 30 minutes of release.
In some members of Rosaceae, Leguminoseae and Solanaceae, viability can be for months.
It is possible to store pollen of a large number of species for years in liquid nitrogen (–196°C) in pollen banks for crop breeding programmes.
Flowering Plants
Much b
All flowering plants INTRODUCTION actual flow
a plant, the
show sexual the plant
flower has
reproduction.
Several ho
structura
Flowers are objects differentia
the floral p
of aesthetic, ornamental,
which
I
social, religious and infloresce
S
cultural value. They have floral bud
Y
always been used as the f
H
symbols for conveying
P
important human
feelings such as love,
L L
affection, happiness,
A
grief, mourning etc.
W
PRE-FERTILISATION-STRUCTURES AND EV
Stamen, Microsporangium and Pollen Grain
Androecium, consists of a whorl of stamens, representing the male repro
A typical Stamen has two parts
Filament A
• It is long slender stalk. • The terminal part
• The proximal end of the filament is attached • Each lobe having
, MICROSPOROGENESIS
Microsporogenesis is a process of formation of microspores from PMC (Pol
As the anther Cells of the Undergoes
develop sporogenous
tissue(PMC) MEIOSIS
Each cell of the sporogenous tissue is a potential pollen The microspores, as they are formed, are arranged in a As
or microspore mother cell. cluster of four cells - the microspore tetrad. di
Sporopollenin is one of most resistant organic material known. It can withstand high temperature, strong acid
it is known. Pollen grains are well preserved as fossil due to it.
POLLEN GRAIN
Pollen grains represent the male gametophytes. A variety of architecture-sizes, shapes, colours, designs are see
Exine
• Outer hard layer
Vegetative cell
I
• Has germ pores
S
Bigger, has abundant
food reserve & a large
Y
irregularly shaped nucleus
P H
Generative cell
Small, floats in the cytoplasm of
Intine
vegetative cell; spindle shaped with
L
dense cytoplasm and a nucleus
Inner wall layer, thin con
A L
Pollen grains are generally spherical; measuring 25-50 micrometers in diameter
W
In over 60 % of angiosperms, pollen grains are shed at 2-celled stage, in the remaining species, generative cell divides mitotically to give rise to
(3-celled Generative cell divides mitotically and form two non motile ame gametes).
Pollen grains of many species cause severe allergies, chronic respiratory disorders, asthma, bronchitis etc e.g., Parthenium (carrot grass) came
became ubiquitous in occurrence & causes pollen allergy.
Pollen grains are rich in nutrients. Pollen tablets and syrups has been claimed to increase performance of athletes & race horses.
Pollen Viability: Highly variable. Depends to some extent on prevailing temperature and humidity.
In some cereals like rice and wheat pollen grains lose viability within 30 minutes of release.
In some members of Rosaceae, Leguminoseae and Solanaceae, viability can be for months.
It is possible to store pollen of a large number of species for years in liquid nitrogen (–196°C) in pollen banks for crop breeding programmes.
