Sexual rep in flowering plant Flashcards
Are we not lucky that plants reproduce sexually? The —- that we enjoy gazing at, the —- that we swoon over, the — that attract us, are all there as an aid to sexual reproduction.
myriads of flowers
scents and the perfumes
rich colours
Flowers do not exist only for us to be used for —.
our own selfishness
All flowering plants (—-) show sexual reproduction. T/F
Angiosperms
True
A look at the diversity of structures of the — , —- and — shows an amazing range of —- to ensure formation of the end products of
sexual reproduction, the — and —-.
inflorescences, flowers , floral parts,
adaptations
fruits and seeds
Human beings have had an intimate relationship with —- since time immemorial.
flowers
Flowers are objects of —- (5) value
– they have always been used as —-for conveying important human feelings such as love, affection,
happiness, grief, mourning, etc.
aesthetic, ornamental, social, religious and cultural
symbols
To a biologist, flowers are — and —marvels and the —-.
morphological and embryological
sites of sexual reproduction
Much before the actual flower is seen on a plant, the — has taken place.
decision that the plant is going to flower
Several — and —- changes are initiated which lead to the differentiation and further development of the —-.
hormonal and structural
floral primordium
Inflorescences are formed which bear the —- and then the —-.
floral buds
flowers
In the flower the male and female reproductive structures, the — and — differentiate and develop.
androecium and the gynoecium
Androecium consists of a whorl of —- representing the male reproductive organ and the — represents the female reproductive organ.
stamens
gynoecium
Two parts of a typical stamen – the —- called the filament, and the —
called the anther.
long and slender stalk
terminal generally bilobed structure
The proximal end of the filament
is attached to the —- of the flower.
thalamus or the petal
The — and —- of stamens are variable in flowers of different species.
number and length
A typical angiosperm anther is — with each lobe having —-, i.e. they are —–
bilobed
two theca, i.e., they are dithecous
Often a —– runs —- separating the theca.
longitudinal groove
lengthwise
The —- of an anther is very distinct in the transverse section of the anther.
bilobed nature
The anther is a —-sided (—) structure consisting of — located at the corners, two in each lobe.
four
tetragonal
four microsporangia
The microsporangia develop further and become —-
pollen sacs.
Pollen sac extend — all through the —- and are packed with —-
longitudinally
length of an anther
pollen grains.
Structure of microsporangium:
In a transverse section, a typical microsporangium appears — in outline.
near circular
Microsporangium generally surrounded by — wall layers – the —, —, — and —–.
four
epidermis, endothecium, middle layers and the tapetum
The — three wall layers perform the function of —- and help in
—- .
outer
protection
dehiscence of anther to release the pollen
The innermost wall layer is
the —. It nourishes the —-.
tapetum
developing pollen grains
Cells of the tapetum possess —-cytoplasm and generally have—-
nucleus.
Can you think of how tapetal cells could become BI-NUCLEATE?
dense
more than one
When the anther is —, a group of —, —– cells called the —- tissue occupies the centre of each
microsporangium.
young
compactly arranged homogenous cells
sporogenous
Microsporogenesis :
As the anther develops, the cells of the —– undergo meiotic divisions to form —-.
What would be the ploidy of the cells of the tetrad?
sporogenous tissue
MICROSPORE TETRADS
As each cell of the sporogenous tissue is capable of giving rise to a
—-. Each one is a —-.
microspore tetrad
potential pollen or microspore mother cell
The process of formation of —- from a —- through meiosis is called microsporogenesis.
microspores
pollen mother cell (PMC)
The microspores, as they
are formed, are arranged in a —-–the —-
cluster of four cells
microspore tetrad
As the anthers — and —-, the microspores dissociate from each other and develop into —
mature and dehydrate
pollen grains
Inside each microsporangium —- of microspores or pollen grains are formed that are released with the —-
several thousands
dehiscence of anther
The —– represent the male gametophytes.
pollen grains
If you touch the —- of Hibiscus or any other flower you would find
deposition of —– on your fingers.
opened anthers
yellowish powdery pollen grains
Sprinkle pollen grains on a drop of — taken on a —- and observe under a microscope. You will really be amazed at the variety of —-– sizes, shapes, colours, designs – seen on the pollen grains from different species
water, glass slide
architecture
Pollen grains are generally —measuring about —- in —-.
spherical
25-50 micrometers
diameters
Pollen has a prominent —-
wall.
two-layered
The —- outer layer called the —- is made up of —-
hard, exine
sporopollenin
Sporopollenin is one of the —-
known.
most resistant organic material
Sporopollenin can withstand —- and —-.
—- that degrades sporopollenin is so far known.
high temperatures
strong acids and alkali
No enzyme
Pollen grain exine has — called —- where sporopollenin is absent.
prominent apertures
germ pores
Pollen grains are well preserved as — because of the presence of —.
fossils
sporopollenin
The exine exhibits a —–
Why do you think the exine should be hard? What is the function of germ pore?
fascinating array of patterns and designs.
The inner wall of the pollen grain is
called the — .
intine
Intine is a— and —- layer made up of —-.
thin and continuous
cellulose and pectin
The cytoplasm of pollen grain is
surrounded by a —-.
plasma membrane
When the pollen grain is
mature it contains — cells, the —-
two
vegetative cell and generative
cell
The vegetative cell is —, has —- and a —- nucleus.
bigger
abundant food reserve
large irregularly shaped
The generative cell is — and floats in the —–.
small
cytoplasm of the vegetative cell
Generative cell is — shaped with — and a nucleus.
spindle
dense cytoplasm
In —- of angiosperms, pollen grains
are shed at this 2-celled stage.
In the remaining species, the — cell divides —- to give rise to the —- before pollen grains are shed (3-celled stage).
over 60 per cent
generative, mitotically
two male gametes
Pollen grains of many species cause —- and —- in some people often leading to — respiratory disorders–—, —–, etc.
severe allergies, bronchial afflictions
chronic
asthma, bronchitis
It may be mentioned that —- that came into India as a — with—-,
has become — in occurrence and causes pollen allergy
Parthenium or carrot grass
contaminant
imported wheat
ubiquitous
Pollen grains are rich in —. It has become a fashion in recent
years to use pollen tablets as food supplements. In western countries, a
large number of pollen products in the form of tablets and syrups are
available in the market. Pollen consumption has been claimed to increase
the performance of athletes and race horses (Figure 2.6).
nutrients
It has become a —- in recent
years to use —- as — supplements.
fashion
pollen tablets
food
In — countries, a large number of pollen products in the form of —- and —- are available in the market.
western (england in pic)
tablets and syrups
Pollen consumption has been claimed to increase the performance of — and —-
athletes and race horses
When once they are shed, pollen grains have to land on the stigma
before —- if they have to bring about fertilisation.
they lose viability
How long do you think the pollen grains retain viability?
The period for which pollen
grains remain viable is —- and to some extent depends on the
—-, —-
highly variable
prevailing temperature and humidity
In some —- such as rice and
wheat, pollen grains lose viability within —-
cereals, 30 minutes of their release,
In some members of —, —, —- they
maintain viability for months.
Rosaceae, Leguminoseae and Solanaceae,
You may have heard of storing —- of many animals including humans for —- .
semen/ sperms
artificial insemination
It is possible to store pollen grains of a —- for —- in —- . Such stored pollen can be used as pollen banks,
similar to seed banks, in —-
large number of species
years
liquid nitrogen (-196C)
crop breeding programmes
The — represents the female reproductive part of the flower.
gynoecium
The gynoecium may consist of a single pistil (—-) or may have
more than one pistil (—-).
monocarpellary
multicarpellary
When there are more than one,
the pistils may be fused together (–) or may be free (—)
syncarpous
apocarpous
Each pistil has three parts
the —, —, —- .
stigma, style and ovary
The stigma serves as a— for pollen grains.
landing platform
The style is the —- part beneath the
stigma.
elongated slender
The —- part of the pistil is the ovary.
basal bulged
Inside the ovary is the ovarian cavity (—). The —- is located inside the ovarian cavity. .
locule
placenta
Arising from the placenta are the —, commonly called —.
megasporangia
ovules
The number of ovules in an ovary may be one (—-) to many (—).
wheat, paddy, mango
papaya, water melon, orchids
The Megasporangium (—-) :
structure of a typical angiosperm ovule
Ovule
The ovule is a — attached to the placenta by means of a — called —.
small structure
stalk == funicle
The body of the ovule fuses with funicle in the region called —.
hilum
Thus, hilum represents the junction between —, —- .
ovule and funicle
Each ovule has one or two protective envelopes called —.
integuments
Integuments encircle the —- except at the tip where a small opening called the — is organised.
nucellus
micropyle
Opposite the micropylar end, is the —-, representing the — of the ovule.
chalaza
basal part
Enclosed within the integuments is a mass of cells called the —.
nucellus
Cells of the nucellus have —-.
abundant reserve food materials
Located in the nucellus is the — or —.
embryo sac
female gametophyte
An ovule generally has a — embryo sac formed from a megaspore
single
Megasporogenesis :
The process of formation of — from the —-.
megaspores
megaspore mother cell
Ovules generally differentiate — megaspore mother cell (MMC) in the — region of the nucellus.
a single
micropylar
MMC is a — cell containing — and a
— nucleus.
large
dense cytoplasm, prominent
The MMC undergoes — What is the
importance of the MMC undergoing meiosis? Meiosis results in the
production of —–megaspores
meiotic division.
four
Female gametophyte :
In a majority of flowering plants, one of the megaspores is —- while the other three —-.
functional
degenerate
Only the functional megaspore develops into the —-
female gametophyte (embryo
sac).
This method of embryo sac formation from a single megaspore is termed —-
What will be the ploidy of the cells of the nucellus, MMC, the functional megaspore and female gametophyte?
monosporic development.
The — of the functional megaspore divides — to form two —- which move to the —-, forming the 2-nucleate embryo sac.
nucleus
mitotically, nuclei
opposite poles
Two more sequential mitotic nuclear divisions result in the formation of the — and —- stages
of the embryo sac.
4-nucleate and later the 8-nucleate
It is of interest to note that these mitotic divisions are —, that is, nuclear divisions are not followed IMMEDIATELY by —
strictly free nuclear
cell wall formation.
After the 8-nucleate stage, — are laid down leading to the — of the typical female gametophyte or embryo sac.
cell walls
organisation
— of the 8 nuclei are surrounded by Cell walls and organised into — while the remaining — called —- are situated —- in the LARGE central cell
6
Cells
2 nuclei- polar nuclei
BELOW the egg apparatus
There is —- of the cells in an embryo sac
Characteristic distribution
— cells are grouped together at micropylar end and constitute —-
3, egg apparatus
Egg apparatus consists of 2 — and 1 —
Synergids
Egg cell
The synergids have —- at the —- tip called —-
Special cellular thickenings, micropylar tip –> filliform apparatus
—– play an imp role in guiding the pollen tubes into the —-
Filliform apparatus
Synergids
Three cells at chalazal end are called —
Antipodal
Large central cell has — nuclei
2 Polar nuclei
Thus a typical angiosperm embryo sac at maturity has —
7 cells tho it is 8 nucleate
