Reproduction in Lower and Higher plants

Maharashtra Board XII th Science
Biology

1. REPRODUCTION IN LOWER AND
HIGHER PLANTS
BIOLOGY
CHAPTER 1
BY Dr. JANAKI V.
PANDEY

2. SEXUALREPRODUCTION
•Fusion of two male and
female gametes.
•The flower is specialized
reproductive organ of plant.
•It produces haploid gametes.
•The process involves meiosis
and fusion of gametes to
form diploid Zygote.
•It produces genetically
dissimilar offspring and leads
to Variation.

3. Sexual reproduction is characterized
by----
1) Fertilization –fusion of male and
female gametes.
2) Formation of zygote
3) Embryogenesis.
Megasporogenesis
Microsporogenesis

4. Flower is reproductive organ.
•The male reproductive organ is androecium.
•Female reproductive organ is gynoecium.
•Androecium
1.Anther
2.Filament
3.Connective
•Gynoecium
1.Ovary
2.Style
3.stigma

5. Anther Ovules
Microsporogenesis
Develops microspore -(PG)
Megasporogenesis
Develops haploid MMC
Development of female gametophyte
(Formation of egg cell & secondary nucleus)
Development of male gametophyte
(Formation of 2 male gametes)
1
st
male gamete + egg cell
Embryo (2n)
2
nd
male gamete + sec. nucleus
Endosperm (3n)
Process of sexual fertilization

6. Structure of anther
Dithecousand tetrasporangiate
i.ehave 4 pollen sacs.
Immature anther
Parenchymatouscell
Archesporialcell.
Sporogenouscell
(Inside)
Primary parietal cell
(outside)
Microspore tetrad.Anther wall layers.

7. T.S. of Anther
1) Epidermis –single layer ,
tubular cells, protective.
2) Endothecium-Radially
elongated cells, fibrosecallose
thickening, hygroscopic.
3) Middle layer-Protection,
disintegrate at maturity.
4) Tapetum-Nutrition,
separation, pollen exine
formation.
5) Microspore mother cell-
meiosis and formation of pollen
grains.
4
1
2
Microspore mother cell (2n) divides
meioticallyto form 4 haploid spores (n)

8. Microsporogenesis
Eachmicrosporemothercelldividestoform
pollengrains.
Structure of microspore
(i.epollen grain).
•Non motile and haploid in nature.
•It is surrounded by 2 layered wall
called sporoderm.

9. •Exine–outer layer, thick, made up of sporopollenin.
•It is resistant to chemicals.
•At some place the wall is very thin–Germ pores.
•Germ pore faciliatespollen tube germination.
•Intine–inner layer, thin, elastic, made up of
cellulose and pectin.
•Forms the pollen tube.

10. Development of male gametophyte
•Pollen grain(PG) is 1
st
stage.
•P G undergoes 1
st
mitotic
divison.
•Produces vegetative and
generative cell.
•Vegetative cell is larger
and nutritive in nature.
•Generative cell is smaller
and further undergoes 2
nd
mitotic division.
•It gives rise to 2 non-
motile male gametes.

11. Anatropous Ovule
V.S. of anatropous ovule shows following parts.
1)Stalk-It is called as funiculus. It attaches main body with
placenta at hilum.
2)Body-shows following parts.
•Nucellus-it consist of central (2n)
parenchymatoustissue.
•Integuments-2 protective covering.
•Micropyle-a narrow opening at the
apex of cell.
•Chalaza-base of ovule present
opposite to micropyle.
•Embryo-female gametophyte.
Oval multicellular structure embededin nucellus.

12. Megasporogenesis
Formation of haploid megaspores from diploid megaspore
mother cell (MMC).
Development of female
gametophyte.
•MMC
meiosis
4
megaspore.
•3 Degenerates and 1
remains functional.
•It undergoes 3 successive,
free nuclear mitoticdivision.
Total 8 nuclei are formed, 4 of which are located at each pole

13. •1 nucleus from each pole move
towards centreand are called
polar nuclei.
•3 nuclei towards micropylarend
forms egg apparatus.
•Egg apparatus has large central
haploid egg cell and 2 haploid
synergids.
•Synergidsshows filiformapparatus
which guide pollen tube towards
the egg.
•3 haploid antipodal cells are present at the chalazalend.
•2 haploid polar nuclei fuse to form diploid secondary
nucleus or definitive nucleus.
Thus, the embryosacshows 8 nucleated and 7 celled structure.

14. Pollination: Itis transfer of pollen grain from anther of one
flower to the stigma of another.
Types of pollination
Self
pollination
Autogamy
Geitonogamy
Cross
pollination
Xenogamy
Hybridization
Transfer of
pollen grains
within
same plant
Transfer of
pollen grains with
other plant
Bisexual flower
is pollinated by its
own pollen grain.
Pollen grains are
transfer from anther
to stigma of another
flower produced on
the same plant
Transfer of pollen
grains from one
flower to another
flower produced on
the different plant
but of same species
Transfer of pollen
grains from one
flower to another
flower produced on
the different plant
but of different sps

15. Self pollination
•Pollen grains are transferred from anther to stigma of
same flower or a different flower produced on the
same plant.
1) Autogamy
•Bisexual flower is pollinated by its own pollen grain.
•Offspring are genetically identical to their parents. eg. Pea.
2) Geitonogamy-
•Pollen grains are transferred to
the stigma of different flower
on the same plant.
•Do not bring genetic variation
but ecologically significance.
Eg. Cucurbitamaxima.

16. Advantages of self pollination
1.Sure method of pollination as no role of external
agents.
2.Economical for plant as no modifications like
attractive flower, nectar, fragrance required.
3.Least wastage of pollen grains.
4.Maintenance of genetic stability or pure line in
progeny.

17. Disadvantages of self pollination
1.No chance of forming improved varieties like
hybrids.
2.No elimination or introduction of characters in
offspring is possible.
3.Continuous self pollination leads to inbreeding
depression.
4.Progenies become weaker, disease susceptible, less
productive & less adoptive.
5.Does not favor variations & evolution.

18. Transfer of pollen grains from anther of one flower to the
stigma of another flower produced on the different plant
of dissimilar genetic makeup.
1) Xenogamy
•Pollen grains are transferred to the
stigma of different flower belonging
to same species.
•Offspring are genetically varied.
Eg. Papaya.
2) Hybridization-
•Transfer of pollen grains from anther of one flower to the
stigma of another flower produced on the different plant of
different species/ variety/ subspecies.
Eg. Pollination between 2 species or varieties of cotton.
Cross pollination

19. Advantages of cross pollination
1.Includes genetic recombination & brings
variations.
2.Characters can be eliminated or introduced in
offspring.
3.Production of improved varieties like hybrids by
hybridization.
4.Progenies are strong, disease resistant,
adaptive to environment & show better vigour.
5.Favors process of evolution.

20. Disadvantages of cross pollination
1.Depends on external carriers, so failure chances are more.
2.Not economical as lot of energy is wasted for attracting
pollinators or carriers.
3.Wastage of pollen grains.
4.Chance of elimination of desirable character or
introduction of undesirable character.
5.Genetic purity of offspring is not maintained.

21. Agents of pollination
Pollinating agents
Abiotic
Wind
Anemophily
Water
Hydrophily
Hypohydrophily Epihydrophily
Biotic
Insects
Entomophily
Birds
Ornihophily
Bats
chiropteryphily
Plants depend upon external carrier or pollinators for the
process of Pollination called as pollinating agents.

22. Pollination by wind-
•Crop plants are wind pollinated.
•Eg. Wheat , rice, maize, palm, etc.
Floral adaptation in anemophilious
flower.
•Flowers are small, inconspicuous, colourless, without
nectar and fragrance.
•Pollen grains are light, dry and produce
large in no.
•Stigma feathery.
•Stamens are exsertedwith long
filaments and versatile anthers.
•Stamens and stigma are exposed
to air.
Single flower
Versatile anther

23. Pollination by water-
•Found only in 30 genera of aquatic monocots.
•Eg. Vallisneria, Zostera, Ceratophyllum,etc.
Floral adaptation of hydrophilousflower.
•Flower are small and inconspicuous.
•Perianth& other floral parts are unwettable.
•Pollen grains are long and
unwettabledue to presence
of mucilage.
•Nectar and fragrance are
absent.

24. Hydrophilyis of 2 types-
1.Hypohydrophily–
•Pollination occur below the
surface of water.
•Pollen grain are heavier than
water, sink down and are
caught by female flowers.
•Eg. Zostera
2. Epihydrophily-
•Pollination occur above the surface of water.
•Pollen grain are lighter and floats on the water surface
(specific gravity of pollen grain = water) and reach the
stigma of female flower.
•Eg. Vallisenaria.

25. 1)Pollination by insects-
•Eg. Rose, Jasmine,Cestrum, etc.
Adaptations in entomophilous
flowers.
1)Large, showy usually brightly coloured.
2)Have fragrance and nectar.
3)Stigma is hairy and sticky.
4)Pollen grains are spiny and
have pollen kit.
5)Special mechanism in some
plants like Salvia-lever
mechanism to help
pollination.

26. 2) Pollination by birds (Ornithophilousplants.)
Eg.Bombax, bottle brush, Butea.
Adaptations in Ornithophilousflowers
1.Flowers are large, showy and brightly coloured.
2.Secrete abundant dilute nectar.
3.Pollen grains are spiny and sticky.
4.Flowers are without fragrance.
5.Corolla is thick, fleshy , tubular or
funnel shaped.

27. 3) Pollination by Bats
•Eg. Anthocephalous, Adansonia,
Kigelia, etc.
Adaptations in chiropterphilous
flowers.
1.Flowers are with dull colourwith
strong odour.
2. Flowers are large and stout.
3. Flowers open during night.
4. Secrete abundant nectar.
5. Flowers produce large
amount of edible pollen grains.
Kigelia
Adansoniaflower pollinated by bat

28. Out breeding devices
Out breeding
devices
Unisexuality
Dichogamy
Protandry
Protogyny
Prepotency
Heteromorphy
Herkogamy
Selfsterility

29. Out breeding devices
Unisexuality
•The plant bears either male or female
flowers. It is also called as dioecism.
•Self pollination is not possible.
•Monoecious: Maize
•Dioecious: Mulberry, Papaya.
Female flower
(Anther sterile)
Male flower
(Ovary non functional)

30. Dichogamy
•Flowers are bisexual but anthers and stigma
mature at different times.
1)Protandry: androecium mature earlier than
gynoecium.
Eg:-disc florets of sunflower.
2)Protogyny: gynoecium mature earlier than
androecium.
Eg:-Gloriosa.

31. Heterostyly/Heteromorphy
•Stigmasandanthersareplacedatdifferent
levels(heterostylyandheteroanthy).
•Thispreventsthepollensfromreachingthe
stigmaandpollinatingit.
Eg:Primrose

32. Herkogamy
•It prevent self pollination in a bisexual flower.
•In plants, natural physical barrier is present
between two sex organs and avoid contact of
pollen with stigma of same flower.
Eg: Calotropis-pentagular
stigma is present above the
level of anther (pollinia).
Stigma
Anther

33. Prepotency-
Pollen grains of other flowers germinate rapidly over
the stigma than the pollen grains from the same flower.
Eg: Apple
Germination of pollen on
stigma of the same flower is
inhibited
Eg: Tobacco, Thea
Selfincompatibility
Flower of
Apple

34. Pollen -Pistil interaction
•All the events from deposition of pollen grain
on stigma to the entry of pollen tube in the
ovule are referred as pollen-pistil interaction.
•During pollination numerous pollen grains
land on the surface of stigma.
•The pistil has ability to recognize
the right pollen of the same
species and discard the wrong
type of pollen.

35. •This recognition is done by special type of
protein.
•Right pollen grain absorbs water and nutrient
from the surface of stigma, germinates and
produce pollen tube.
•Pollen tube moves through the style
and reaches embryo sac.
•The tip of the pollen tube enters in
one of the synergids, ruptures it
and release 2 male gametes.

36. Artificial Hybridisation
•It is one of the crop improvement technique.
•Desired pollen grain are hand pollinated and
used for fertilization.
•The procedure used is emasculation and
bagging.
Emasculation
Bagging

37. Entry of pollen tube
Pollen tube penetrates the embryo sac by different pathways.
a)Porogamy–pollen tube enters ovules through micropyle.
b)Chalazogamy-pollen tube enters ovules through chalaza.
c)Mesogamy-pollen tube enters ovules through integuments.

38. Doublefertilization
•Pollen tube enters the ovule through the
micropylarend.
•It carries 2 male gametes & penetrates one
of the Synergids.
•The synergidsruptures and
releases the 2 non motile
male gametes in embryo sac.
•As non motliemale gametes
are carried through hollow
pollen tube, it is known
as siphonogamy.

39. •1
st
male gamete fuse with the egg cell.
The fusion is called Syngamy.
•It forms diploid Zygote which develops
into Embryo.
•2
nd
male gametes fuses with secondary
nucleus to form primary
endosperm nucleus.
•The fusion is called as triple
fusion.
•Primary Endosperm Nucleus
(PEN) develops into triploid
endosperm.

40. Significance of Double Fertilization
1.Fertilization stores food material in seed.
2.Diploid zygote develops into an embryo
3.The triploid PEN develops into nutritive
endosperm tissue.
4.It restores the diploid condition by fusion of
haploid male gamete with haploid female
gamete (i.e. through syngamy).
5.It also helps to avoid polyembryony.

41. Development of Endosperm
•The triploid PEN repeatedly divide mitotically
to form Endosperm.
•There are 3 types of Endosperm.
1.Nuclear endosperm
2.Cellular endosperm
3.Helobialendosperm

42. Nuclear endosperm
•Primary endosperm nucleus repeatedly divides
mitotically without wall formation to produce
large number of free nuclei.
•A big central vacuole appears in the centreof cell
pushing the nuclei towards the periphery.
•Later it forms multicellular endosperm by cell
wall formation.
•In certain cases cell wall
formation remains
incomplete.
•Eg. Wheat, sunflower and
coconut.

43. Cellular Endosperm
•In some plants, division of triploid primary
endospermic nucleus is immediately followed
by wall formation.
•So that the endosperm is cellular right from
the beginning.
•Eg:Balsam, Petunia,
Adoxa, etc..
Petunia

44. HelobialEndosperm
•It is intermediate between
cellular and nuclear type.
•First divisonof primary endo-
sperm nucleus is followed by a
transverse wall, which divides
the cell unequally.
•The smaller cell is called chalazal
cell and larger cell is the micropylarcell.
•Then the nuclei in each cell divide by
free nuclear divisions and then walls
develop between nuclei in
micropylarchamber.
•Eg. Asophodelus. Asophodelus

45. Development of embryo
The development of a Zygote into embryo is called embryogenesis
Development of dicot embryo

46. Embryogenesis
Zygote
Proembryo
Suspensorinitial cellEmbryonalinitial cell
Filamentous suspensor
(6-10 cells)
1
st
cellformshaustorium
Lower most cell hypophysis
Octant (8 celled)
Lower tier form hypocotyl
And radicle
Upper tier forms plumule
and cotyledon
Heart shaped
2 lateral cotyledon
And terminal plumule
Part of radicle
And root cap
Horse shoe shaped
(by curvature of embryo)
Divide in several plane
Smaller cell towards
chalaza
Larger cell towards
micropyle

47. Development of monocot embryo
•In moncotembryo, single cotyledon occupy terminal position and
plumuleis lateral.
•Shield shaped cotyledon is called scutellum.
•The protective covering of plumuleis called coleoptile & radicle is
coleorhiza.

48. Seed and fruit development
•Ovules develops into seed.
•Integuments develops into seed coat.
•Seeds have 2 coverings –testaand
tegmen.
•Ovary develops into
fruit.
•The covering of fruit
is called Pericarp.

49. Endospermic or albuminousseed
•In some seeds, the food reserves in the
endosperm are partially used up by the
development of an embryo.
•In such seeds the endosperm remains
conspicuous and fills a greater part of the
seed.
•Thus, the resultant
seed is endospermic
or albuminous.
Eg. Castor, coconut, maize,
etc.

50. Non-Endospermic or exalbuminousseed
•In some seeds, embryo absorbs food
reserve from the endosperm
completely during its developmental
stages.
•Thus, endosperm disappears
in mature seeds.
Eg. Pea, bean, etc

51. Significance of fruit and seed formation
•Fruits provide nourishment to the
developing seeds.
•Fruits protect the seeds in immature
condition.
•Seeds serve as important propagating
organs (units) of plant.
•Seeds and fruits develop special devices for
their dispersal and thus help in the
distribution of the species.

52. Dormancy
•Mature and viable seeds will not
germinates even though
favourableconditionis present.
•Dormancy is very important for the
dispersal of seed.
•Lupinusarcticus-10,000 yrs.
•Phoenix dactylifera-2000 yrs.
(Date palm)
Seed of Lupinus
Lupinus
Date palm

53. Apomixis( apo= away, mixis=mixing)
•Formation of embryo through asexual
method of reproduction without formation of
gametes and fertilization.
•Diploid sporophyte cell produces a diploid
gametophyte without undergoing meiosis is
called apospory.
Eg: Orange, Mango
•When a gametophyte cell produces embryo
like structure without fertilization, it is
termed as apogamy.

54. Categories of Apomixis
1.Recurrent apomixis-
•The embryo sac generally rise either from an
archesporialcell or from some other part of the
nucellus.
•In diplospory, the unreduced embryo sac is derived
from the diploid megaspore mother cell e.g. Taraxacum.
•In apospory, the nucellarcells give rise to apomictic
embryo sac.

55. 2. Non-recurrent apomixis
•Megaspore mother cell undergoes usual meiotic division
and a haploid embryo sac is formed.
•Embryo arises either from the egg by parthenogenesis
or from some other haploid cells of gametophyte
through apogamy.
•Plants produced by this method are generally sterile
and do not reproduce sexually,
Eg: Nicotiana.
No fertilization
Non-recurrent apomixis

56. 3. Adventitiveembryony
•Embryos may develop from somatic nucellusor
integuments along with normal zygotic embryo.
•It gives rise to a condition called polyembryony.
E.g: Mango, Orange

57. Parthenocarpy
•It is the condition in which fruit is developed without
the process of fertilization.
•Ovary produces auxinIAA (Indole-3 Acetic Acid) which
is responsible for enlargement of ovary into fruit.
•The fruit resembles the normally produced fruit but it
is seedless.
Eg: Pineapple, Banana, Papaya.

58. Polyembryony
It is the occurrence of more than one embryo in a
seed.
It is of 2 types-
1.Adventive polyembryony-an embryo develop
directly from the diploid cell of nucellusand
integuments.
Eg: Citrus
2.Cleavage embryony-zygote proembryosometimes
divides (cleaves) into many parts or units. Each
unit then developesinto an embryo.
Eg. Pinus

59. Significance of ployembryony
•Increases the chance of survival of new plants.
•Nucellaradventive polyembryonyis of great
importance in horticulture.
•Propagation of fruit tree, such as citrus and mango.
•Can be used for the development of homozygous
diploid.
•Artificial production of these embryos from the eggs
or synergids.