mode of reproduction in crop plants, mode of pollination

1. Reproductive System In Plants
•Breeding procedure depends upon:
Mode of reproduction
Pollination of crop species

2. Cell Division
• Cell division id of 2 types:
1. Mitosis
2. Meiosis
MITOSIS:
• Cell increases in number
• Mitotic cell division takes place in somatic cells
resulting in growth of organism
• Two identical daughter cells produced from
mother cell.
• It has 5 stages: Interphase, Prophase,
metaphase, Anaphase, Telophase

3. It has 5 stages: Interphase, Prophase, metaphase,
Anaphase, Telophase

4. Meiosis
• Meiotic cell division occurs in reproductive organs
during gamete formation
• Reduce the chromosome no. from diploid (2n) 
haploid (n)
• Two divisions of cytoplasm and one duplication of
chromosome occurs
• 1st Meiotic division: Reductional Division 2
daughter cells formed with half chromosome
number
• 2nd meiotic division: Similar to mitotic division

6. MODE OF REPRODUCTION
Asexual
Reproduction:
•Vegetative
reproduction
•Apomixis
•Adventive
embryony
Sexual
Reproduction:
•Autogamy
•Allogamy

7. Asexual Reproduction
Vegetative
reproduction
Vegetative parts:
rhizomes, tuber, corn,
bulbs
Cutting and grafting:
Stem, roots
Apomixis
Parthenogenesis:
embryo from egg cell
without fertilization
Apogamy: embryo
from either synergids
or antipodal cells
Apospory : embryo
from egg cell or
embryo sac
Adventive
embryony
Embryo directly
formed from
vegetative cells of
ovule like nucleus,
chalaza and
integuments

8. Role of apomixes in plant breeding
Rapid production
of pure lines
Maintenance of
superior genotypes
Conservation of
heterosis

9. Significance of asexual reproduction
• It leads to perpetuation of same genotype with
great conservation
• Large no. of genetically identical genotypes can
be obtained irrespective of degree of
heterozygosity
• Desirable clone can be maintained
• Mutation breeding is easy in vegetative produced
plants
• Polyploidy breeding is also very useful as induced
bud can be used as propagule and polyploidy can
be maintained

10. Sexual reproduction
Process involves fusion of male and female gametes to
form seed and it is also called Amphimixes
Flower has special structure for reproduction
• Androecium  Stamen
• Gynoecium Carpel
Sporogenesis: production of microspore and megaspore
• Microspores are produced in anthers  Microsporogenesis
• Megaspores are produced in ovule  Megasporogenesis

11. Microsporogenesis
• Anther has 4 pollen sacs, with numerous
pollen mother cells (PMCs)
meiosis
• Each PMC-------- 4 haploid cells
(microspores)pollen grains(by thickening of
cell wall)

13. Megasporogenesis
• Occurs in ovules inside ovary
• Each single cell in ovule differentiates into
Megaspore Mother cell  undergo meiosis
4haploid megaspores 3 haploid megapores
degenerates
• One functional megaspore per ovule obtained

15. Difference between microsporogenesis
and megasporogenesis
Microsporogenesis Megasporogenesis
It is meiotic formation of haploid
microspores from diploid microspore
mother cell.
It is meiotic formation of haploid
megaspores from diploid megaspore
mother cell.
The arrangement of microspores in a
tetrad is generally tetrahedral.
The arrangement of megaspores in a
tetrad is commonly linear.
All the four microspores of a spore terad
are functional.
Only one megaspore of a spore tetrad is
functional.
Micro sporogenesis is found inside
microsporangium.
It is found inside a megasporangium.
A large number of microspore mother
cells are functional in a microsporangium.
Generally a single megaspore mother cell
is functional in a mega sporangium.

17. Gametogenesis
Production of male and female gametes in microspore and
megaspores.
Microgametogenesis: production of male gamete/sperm
• During pollen maturation, microspore nucleus divides mitotically produce: ->
• generative nucleus
• Vegetative/tube nucleus
• When pollination occurs  pollen germinates
• Pollen tube enters the stigma and grows through style
• Generative nucleus undergo mitotic division to produce 2 sperms
• Pollen tube enters the ovule through micopyle, and discharge 2 sperms into
embryo sac

19. Megagametogenesis : Nucleus of functional
megaspore divides mitotically to produce 4 or more
nuclei
Generally, Megaspore nucleus undergo 3 mitotic divisions to produce
8 nuclei:
• 3 moves to one pole and produce a central egg cell and 2 synergid cells, 1 synergid on
either side of egg cell
• Another 3 migrate to opposite pole, forms antipodal cells
• 2 remains in the centre, polar nuclei that fuse to form secondary nucleus.
Thus, megaspore develops into a embryo sac /megagametophyte is
called megagametogenesis

21. Fertilization
• Fusion of one of the sperm with egg cell produce diploid zygote is
fertilization
– Zygote divide mitotically to produce a diploid embryo
• Fusion of remaining sperm with secondary nucleus to form a
triploid primary endosperm nucleus is Triple fusion
– Triploid primary endosperm mitotically divide repeatedly to form
endosperm
– During seed development, endosperm provides nutrition to
developing embryo
• One male gametes unite with the eggs cell known as syngamy or
fertilization and another male gamete fuse with the pollar nuclei
known as triple fusion, when these two processes occurs
simultaneously known as double fertilization

23. Mode Of Pollination
Depending on nature of pollination plants can be categorized as self
and cross pollinated
Autogamy/ self fertilization: Transfer pollens from anther to stigma of
same plant
• Leads to homozygosity
• Several mechanism : bisexualiy, homogamy, cleistogamy, chasmogamy
Allogamy/ cross fertilization: pollen grains transfer from anther of
one plant to stigma of another plant.
• Leads to heterozygosity
• Several mechanism: monecy, dioecy, dichogarny, heterostyly, herkogamy, self
incompetibility, male sterlity

24. Autogamy/ self pollination
Bisexuality
• male and female organ on same plant
Homogamy
• anther and stigma of flower matures at same time
Cleistogamy
• pollination and fertilization occurs in unopened flower bud
• Wheat, oats and barley
Chasmogamy
• flower opens only after completion of pollination
• Wheat, oats, barley and rice

25. Allogamy / cross pollinated
Dicliny/unisexuality
• Monecy: Same plant but different male female flowers
• Maize, banana, castor and mango
• Dioecy: Staminate and pistillate flowers on different plants
• Papaya and spinach
Dichogamy
• Stamen and pistil of hermophrodite plant mature at different times
• Protandry: maize and sugarbeat (stamen mature before pistil)
• Protogyny: bajra (pistil mature first)
Heterostyly
• Styles and filament of flower are of different length
Herkogamy
• Due to physical barrier like hyline membranearound anther

26. • Inability of fertile pollen to fertilize the same flower
• Brassica, radish, rye and nicotiana
Self incompatibility
• Pollen grains are non functional
• Types: Genetic (GMS), Cytoplasmic (CMS), CGMS
and Transgenic
Male Sterility
Allogamy

27. Autogamous species
• Cereals: Rice, wheat, barley, oats
• Legumes: chickpea, pea, cowpea, lentils, green gram,
black gram soya bean, moth bean
• Oilseeds: Sesame, linseed
• Vegetables: tomato, okra, brinjal, peanut, chillies
Seed propagated
• potato
Vegetative propagated

28. Allogamous species
• Cereals: maize, pearlmillet, rye
• Legumes: alfaalfa, red clover, white clover, sweet clover
• Oilseeds: some brassica strains {B. campestris}, sunflower,
castor
• Vegetables: cabbage, carrot, cauliflower, cucumber, onion,
radish, turnip, sewwt potato
Seed propagated
• Sugarcane, coffee, rubber, grapes, banana
Vegetative propagated

29. Genetic constitution of allogamous
species
Preserve and promote
heterozygosity
Show mild  severe inbreeding
depression and heterosis
Hybrid and synthetic varieties are
the aim of breeder

30. Often Allogamous Species
•Cross pollination exceeds 5% to
30%
•Sorghum, cotton, triticale, rai,
pigeonpea and tobacco, jowar,
jute,
Seed propagated

31. Relevance of Mode of Reproduction
• It determines:
– Genetic constitution
– Nature of gene action
– The ease in pollen control
– Stability of varieties after realease