This document discusses plant reproduction, including asexual and sexual reproduction. It describes the processes of meiosis, gamete formation, fertilization, embryogenesis and seed formation. It discusses pollination methods including biotic and abiotic pollination. Key plant structures are defined, such as flowers, their parts, and fruits. The roles of hormones and environmental factors in flowering are also summarized.

1. By - NM Spirit
T- 931-102-2687
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2. Plant reproduction
Plants have two choices for reproduction:
 Asexual Reproduction
Sexual Reproduction
Asexual reproduction – vegetative growth
Portion of the plant is taken from the mature
sporophyte and used to create a brand new plant
this results in a genetically identical progeny
this is an advantage if the plant shows superior qualities
e.g. Mcintosh apple
e.g. varietal grapes
Disadvantage because there is no genetic
variability which is crucial for the health of
the plant as a species

3. Sexual reproduction – Production of sex
gametes followed by their fusion and the creation
of an embryo that is reliant upon the female
gametophyte
Diploid sporophyte produces haploid spores via
meiosis
The spores divide by mitosis to generate a gametophyte
The gametophyte contains the small male and female
haploid plants that produce gametes
Fertilization results in the production of a diploid
zygote which eventually becomes a diploid
sporophyte via mitosis
Plant reproduction

4. Angiosperms
 Sexual reproduction involves flowers and seeds.
 Flowering can be controlled by hormones, genes and/or
environmental factors.
Angiosperms produce flowers
Flowers with both male and female reproductive
organs are perfect flowers.
Flowers that have only male or only female
reproductive organs are imperfect flowers.
Some angiosperms produce separate male and
female flowers (imperfect flowers).
Monoecious plants
Dioecious plants

5. Haploid (n)
Diploid (2n)
Key
Simplified angiosperm life cycle
Germinating
seed
Seed
Seed
Simple fruit
Embryo (2n)
(sporophyte)
Zygote
(2n)
FERTILIZATION
Egg (n)
Sperm (n)
Embryo sac (n) (female
gametophyte)
Ovule
Ovary
Germinated pollen grain
(n) (male gametophyte)
Pollen
tube
Anther
Mature
sporophyte
plant (2n)
Simplified
angiosperm life
cycle
Angiosperms

6. Flowers
Flowers – Reproductive shoots of the angiosperm
sporocyte.
Composed of four whorls of floral organs: sepals,
petals, stamens and carpels
Pistil – Single carpel or a fused carpel
Complete flowers have all four of these floral
organs
All have functional stamens and pistil
Incomplete flowers lack one or more
Some have functional reproductive parts
Most incomplete flowers have either a stamen
or a pistil
Stamens – Staminate flowers
Pistil – Pistillate flowers or Carpellate

7. Stamen Anther
Filament
An idealized flower
Receptacle
Petal
Carpel
Sepal
Ovary
Style
Stigma
Flowers

8. Flowers can be described using the following:
1. Symmetry
a. Bilateral symmetry: the flower can be divided into
two equal parts by an imaginary line ,e.g. orchid.
b. Radial symmetry: sepals, petals, stamens and
carpels radiate out from a center .e.g. daffodil.
2. Ovary location
a. Superior ovary: ovary is located above the receptacle
b. Inferior ovary: located within the receptacle
c. Semi-inferior : in between
Flowers

9. Flowers
3. Floral distribution – Vary from individual flowers
to clusters of flowers called inflorescences
 e.g. sunflower – center is an aggregation of incomplete
flowers that do not develop
 in each undeveloped flower are the male and female
reproductive parts of the flower or they may be sterile
4. Reproductive variations – presence of staminate
and carpellate flowers on the same plant is a
monoecious plant (bisexual)
 Presence of either staminate or carpellate flowers
 dioecious plant (unisex)
Flowers

10. Copyright reserved.  2012 The E Tutor
Reproductive Structures
Reproductive Floral Structures:
Stamen – male reproductive structure
Anther – sac where pollen in produced
Filament – stalk that supports anther
Carpel (Pistil) – female reproductive structure
Stigma – sticky area on top of carpel that receives
pollen
Style – tube that connects stigma to ovary
Ovary – base of carpel that contains ovule and egg
sac

11. Copyright reserved.  2012 The E Tutor
11
Stamen
Anther
Filament
Carpel
Stigma
Style
Ovary
Ovule
Petal
Receptacle
Sepal all stamens = Androecium
all carpels = Gynoecium
all petals = Corolla
all sepals = Calyx
Male
structure
Female
structure
Reproductive Structures

12. Control of Flowering
Photoperiodism – Plant response to light
involving relative lengths of day and night.

13. Control of Flowering
Control of Flowering
 Long-day plants – Bloom when days are longest and
nights are shortest (mid-summer).
 Short-day plants – Bloom in spring, late summer, and
autumn when days are shorter and nights are longer.
 Day-neutral plants – Day-length not important for
flowering.
 Day length is not as critical as night length in regulation of
flowering.

14. Control by light is due to a pigment in plants called
phytochrome.
Phytochrome – Blue-green pigment that controls
various growth responses (including flowering) in
plants
Two forms of phytochrome:
Pr – Inactive form
Pfr – Active form
Control of Flowering

15. Control of Flowering

16. Pollination
 Pollination is the process by which pollen is
placed on the stigma
 Self-pollination: Pollen from a flower’s anther
pollinates stigma of the same flower.
 Cross-pollination: Pollen from anther of one flower
pollinates another flower’s stigma.
Self PollinationCross-pollination

17.  Successful pollination in many angiosperms depends on
regular attraction of pollinators
 Flowers & animal pollinators have coevolved resulting in
specialized relationships
Pollination
-Bees are the most
common insect
pollinators

18. Flower traits that attract different pollinators are
known as pollination syndromes
Many ways to pollinate a female stigma
1. Wind
2. Water
3. Insect
4. Animal
Pollination

19. Pollination life
Cycle
Pollination

20.  Biotic pollination: Pollination by animals (organisms)
80% of all pollination is biotic
Entomophily – pollination by insects
e.g. bees, wasps, ants, beetles, moths and butterflies
Zoophily – pollination by animals
e.g. birds and bats
 Abiotic pollination: Pollination by non-animal factors
Amenophily
Pollination by wind (98% of abiotic pollination)
Hydrophily
Pollination by water (aquatic plants)
Pollination

21.  Self- pollinization – pollen moves to the female part of
the same flower or to another flower on the same plant
also called autogamy
self pollination is restricted to those plants that accomplish
pollination without an external pollinator
e.g. stamens actually grow in contact with the pistil
plants adapted to self-pollinate have stamens and carpels at
the same length
Cleistogamy – pollination that occurs before the flower
opens
flower is called a cleistogamous flower
these flowers MUST be self compatible or self-fertile
Many crop plants are self-pollinating
peas, corn and tomatoes
routinely self-pollinate
Pollination

22. Pollination
Cross-pollination – between a pollinator and
an external pollinizer
also called syngamy
pollen is delivered to a flower of a different plant
plants adapted to cross-pollinate have taller stamens
than the carpels – e.g. thrum type flower
e.g. apple crops – due to the grafting of most apple
species – gives rise to a genetically identical orchard
Pollination

23. Fertilization
 Pollen grain germinates on stigma, a pollen tube grows
down the style and enters the ovule through the
micropyle.
 The tube cell leads the way through the pollen tube.
 The generative cell divides forming 2 sperm which follow
the tube cell to the micropyle.
 One sperm fuses with the egg to form the zygote (2n),
 The other fuses with the polar nuclei to form the
endosperm (3n).
 This is called double fertilization.

24. After double fertilization, the ovule develops into
the seed (embryo, endosperm and integuments)
Endosperm development – usually precedes
embryo development
the triploid nucleus divides and produces a multinucleate
“supercell” with a milky consistency
cytokinesis then converts the multinucleate cell into a
multicellular endosperm
these “naked” cells will eventually produce cell walls and the
endosperm will become solid
the “milk” of the coconut is an example of liquid endosperm
and the “meat” is an example of a solid endosperm
if the endosperm is used during the development of
the cotyledons then the seed will lack an
endosperm as it matures
Fertilization

25. Embryo development – first mitotic division of the
zygote results in an embryo
splits the zygote into a basal cell and a terminal cell
terminal cell gives rise to most of the embryo
the basal cell continues to divide transversely and
produces a thread of cells = suspensor
the suspensor is the “umbilical cord” anchoring the
embryo to its parent
functions in the transport of nutrients to the embryo
from the parent
in some plants the suspensor functions in the transfer of
nutrients from the endosperm
Fertilization

26. Stigma
Pollen tube
2 sperm
Style
Ovary
Ovule (containing female
gametophyte, or embryo sac)
Micropyle
Polar
nuclei
Egg
If a pollen grain
germinates, a pollen tube
grows down the style
toward the ovary.
Pollen
grain
Fertilization

27. Ovule
Polar nuclei
Egg
Two sperm
about to be
discharged
The pollen tube
discharges two sperm into the
female gametophyte (embryo
sac) within an ovule.
One sperm fertilizes
the egg, forming the zygote.
The other sperm combines
with the two polar nuclei of
the embryo sac’s large
central cell, forming a
triploid cell that develops
into the nutritive tissue
called endosperm.
Endosperm nucleus (3n)
(2 polar nuclei plus sperm)
Zygote (2n)
(egg plus sperm)
Fertilization

28. Seeds
 The terminal cells divides multiple times to produces a
spherical proembryo attached to the suspensor
 The cotyledons begin to form as bumps on the proembryo
Eudicot is heart shaped at this stage
in the monocot only one of these bumps will go on to form a
cotyledon
 After the rudimentary cotyledons form – the embryo
elongates
cradled between the two cotyledons in the eudicot is the
embryonic shoot apex including the shoot apical meristem
at the other end of the embryo where the suspensor
attaches is the root apex with its RAM

29.  The seed develops specific structures depending on whether
it is a monocot or a eudicot
 Eudicot – bean
 elongated embryo – embryonic axis
 contains two developing cotyledons attached to the embyro
 below where these cotyledons attach to the embryo – hypocotyl
 the hypocotyl terminates in the radicle – embryonic root
 above the attachment of the cotyledons is the epicotyl – shoot
tip with a pair of miniature leaves
 the majority of the bean is the starch-filled cotyledons
 Eudicot – castor bean
 reduced cotyledons in size retain their food supply
in the endosperm rather than the cotyledons
 the cotyledons receive their nutrition from the
endosperm and transfers it to the rest of the embryo
as it grows
Seeds

30. Seeds
Seed coat Epicotyl
Radicle
Hypocotyl
Cotyledons
Common garden bean, a eudicot with thick cotyledons
Seed coat
Cotyledons
Epicotyl
Radicle
Hypocotyl
Endosperm
Castor bean, a eudicot with thin cotyledons

31.  Monocot – corn kernel
 single cotyledon
 in the grass family (including corn and wheat) – the
cotyledon is specialized and forms a scutellum
 The embryo of grasses is enclosed within two shields:
 Coleoptile which covers the shoot
 Coleorhiza which encloses the young root
 During the last stages of seed maturation – the seed
dehydrates until about 5-15% total water content and
becomes covered by the integuments which have
hardened into a seed coat
 the cotyledons and embryo become dormant
Seeds

32. Maize, a monocot
Coleoptile
Epicotyl
Radicle
Hypocotyl
Endosperm
Pericarp fused
with seed coat
Coleorhiza
Scutellum
(cotyledon)
Seeds

33. Fruits
 While the seed is developing from ovules, the fruit is
developing from the ovary.
 Fruit = Ripened ovary + Seeds of a flowering plant.
 Fruit protects the developing seeds and will participate in
their dispersal using wind or animals.
 Two main types of fruits: dry and fleshy
 Dry fruits – The ripening of a dry fruit involves the aging
and drying of the fruit tissues.
 Fleshy fruits – A complex series of hormonal changes
results in an enticing edible fruit that attracts animals
 the fruits pulp becomes softer due to enzymes that digest
components of the cell wall.
 usually a color change from green to another color
 organic acids and starch increase in concentration
 sweet or tart fruit

34.  Fertilization of the egg triggers a series
of hormonal events that triggers the
development of the ovary into the fruit.
 As the fruit develops, the other parts of
the flower die and drop away
 Tip of the pea pod is the remnant of the
stigma
 The fruit ripens about the same time
the seed has finished its development
 Accelerated through the production of
ethylene
 Pollination precedes fertilization
– therefore fruit development is usually
a sign of pollination.
Fruits

35.  As the fruit develops the outer wall of the ovary thickens
and develops into the pericarp
Tissue that develops and surrounds a seed
Develops from the wall of the ovary
In some fruits the pericarp can become dry and hard and
form a shell
 In fleshy fruits the pericarp can be divided into several
regions:
Exocarp – or epicarp
Tough outer skin of the fruit or the peel
Mesocarp – or sarcocarp
Botanical term for the succulent and fleshy middle layer of the
pericarp
Usually the part of the fruit that is eaten
Endocarp – hard inner layer of the pericarp of
some fruits that contains the seed
Fruits

36. Types of fruits
 Several types of fruits depending on their developmental
origin
1. Simple: derived from a single carpel or several fused
carpels within one pistil
Can be either fleshy or dry
The dry fruits can either be dehiscent (opening to discharge
seeds) or indehiscent (not opening to discharge seeds)
If the pericarp is fleshy – fruit is known as a simple fleshy fruit
e.g. apple, peach, pea, wheat, coconut, carrot, radish, tomato.
2. Aggregate – results from a single flower that has
more than one separate carpel with each forming
a separate “fruitlet”
Develops from multiple simple pistils with one carpel each
The fruit is frequently called a “druplet” (raspberry) or a
bramble (blackberry).

37. Types of fruits
Stamen
Stigma
Ovary
Pea flower
Ovule
Seed
Pea fruit
Simple fruit
Stamen
Stigma
Ovary
Raspberry flower
Aggregate fruit
Stamen
Carpels
Carpel
(fruitlet)
Raspberry fruit

38. 3. Multiple – develops from
an influorescence (a group
of flowers tightly clustered
together) – the walls of the
ovaries thicken and fuse
together
 e.g. pineapple, mulberry,
breadfruit
 There are fruits in which
structures other than the ovary
contribute to the formation of
the fruit
 These fruits are called accessory
fruits or false fruits
Types of fruits
Pineapple inflorescence
Multiple fruit
Flower
Each
segment
develops
from the
carpel
of one
flower
Pineapple fruit

39. Seedless fruits
 Seedlessness is an important feature
of fruit crops like bananas,
pineapples, grapes, watermelons,
some citrus fruits (navel oranges,
tangerines).
 In some species, seedlessness is the
result of parthenocarpy: Fruits set
without fertilization
May or may not require pollination
 Some fruits will become seedless if
the plant does not undergo
pollination but will develop seeds if
pollination takes place and results in
fertilization within the ovules
– e.g. pineapple, cucumber

40. Seed Germination
 As a seed matures it dehydrates and enters a dormancy
phase – low metabolic rate in the embryo and a suspension
of its growth and development.
 Conditions required to break this dormancy varies from
plant to plant.
– e.g. once they reach a suitable environment.
– e.g. some require a specific environmental cue.
 Seed dormancy increases the chances that the seed will
germinate under favorable conditions.
 Environmental conditions
 Desert plants – require substantial amounts of water.
 Trees – heat provided by fires.
 Extended exposure to cold.
 Lettuce – requires increased light.

41.  Germination depends on the physical process called
imbibitions.
uptake of water due to the lower water potential of the dry
seed
causes the seed to expand and rupture its coat
also triggers metabolic events in the embryo that enables it
resume its development
as the embryo grows it makes digestive enzymes which
digests away the stored foot in the seed (endosperm or
cotyledons)
first organ to emerge is the embryonic root – the radicle
the shoot tip then forms and breaks through the soil surface
Seed Germination

42.  In many eudicots and beans – a hook forms in the
hypocotyl and this hook is pushed through the soil –
stimulated by light to straighten which raises the
cotyledons and the epicotyl.
 The shoot apex is actually pulled upward rather than being
pushed tip first through the abrasive soil.
 The epicotyl spreads its first leaves which are called true
leaves as apposed to the “seed leaves” or the cotyledons.
 In monocots breaking ground is accomplished by the
coleoptile.
 The sheath enclosing the coleoptile pushes upward through
the soil and into the air.
 The shoot tip grows through the tunnel forming
within the growing coleoptile.
 The shoot then breaks through the tip of the coleoptile.
Seed Germination

43. Seed Germination
Foliage leaves
Cotyledon
Cotyledon
Hypocotyl
Hypocotyl
Radicle
Seed coat
Hypocotyl
Cotyledon
Epicotyl
Common garden bean

44. The End
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