Double fertilization in plants, Monocot and Dicot embryo, Endospermic and Non-endospermic seeds.

1. Artificial hybridisation

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3. Artificial hybridisation
• Artificial hybridization is the process in which only
desired pollen grains are used for pollination and
fertilization.”
• Artificial hybridisation is one of the major approaches of
crop improvement programme.

4. Artificial hybridisation
• Emasculation
• Bagging
• Rebagging.

5. Emasculation
• The process of removal of anthers from the
flower bud before the anther dehisces using a
pair of forceps is called Emasculation.

6. Bagging.
• Emasculated flowers have to be covered with a
bag of suitable size.
• The bag made up of butter paper.
• To prevent contamination of its stigma with
unwanted pollen.
Butter paper is a non-
sticky cellulose-based
paper..

7. Rebagging:
• When the stigma of bagged flower attains receptivity,
mature pollen grains collected from anthers of the male
parent are dusted on the stigma..
• The flowers are rebagged and the fruits allowed to
develop.

8. • If the female parent produces unisexual flowers,
there is no need for emasculation.
• The female flower buds are bagged before the
flowers open..

9. Siphonogamy
• Siphonogamy is a condition in plants in which
pollen tubes are developed for the transfer of
the male cells to the eggs.
• The seed plants are siphonogamous..

10. Double fertilisation

11. Double fertilisation

12. Syngamy.
• One of the male gametes moves towards the egg
cell and fuses with its nucleus thus completing
the syngamy.
• This results in the formation of a diploid cell, the
zygote

13. Triple fusion
• The other male gamete moves towards the two
polar nuclei located in the central cell and fuses
with them to produce a triploid primary
endosperm nucleus (PEN)..
• This involves the fusion of three haploid nuclei it
is termed triple fusion.

14. • Since two types of fusions, syngamy and triple
fusion take place in an embryo sac the
phenomenon is termed double fertilisation.

15. Post-fertilisation : structures and events
• endosperm development,
• embryo development,
• maturation of ovule(s) into seed(s)
• ovary into fruit, ………are collectively termed
post-fertilisation events.

16. Endosperm
• Endosperm develops before the embryo.
• Because the cells of the endosperm provide
nutrition to the developing embryo.

17. Endosperm
• The primary endosperm cell divides repeatedly
and forms a triploid endosperm tissue.
• The cells of this tissue are filled with reserve food
materials and are used for the nutrition of the
developing embryo.

18. Free nuclear and Cellular endosperm
• The PEN undergoes successive nuclear divisions to give
rise to free nuclei.
• This stage of endosperm development is called free-
nuclear endosperm.
• Subsequently cell wall formation occurs and the
endosperm becomes cellular.

19. • The coconut water from tender coconut that you are
familiar with, is nothing but free-nuclear endosperm
(made up of thousands of nuclei) …
• The surrounding white kernel is the cellular endosperm.

20. Endosperm development

21. • Endosperm may either be completely consumed by the
developing embryo (e.g., pea, groundnut, beans) before
seed maturation.
• Endosperm persist in the mature seed (e.g. castor and
coconut) and be used up during seed germination.

22. • Endosperm is persistent in cereals – wheat, rice
and maize.

23. Embryo development
• Embryo develops at the micropylar end of the
embryo sac where the zygote is situated.
• Most zygotes divide only after certain amount of
endosperm is formed.

24. • The early stages of embryo development
(embryogeny) are similar in both
monocotyledons and dicotyledons…
• The zygote  proembryo  globular 
 heart-shaped  mature embryo.

26. Haustorial
cell

29. • Zygote divides asymmetrically giving rise to a
terminal cell and a basal cell..
• The terminal cell (Apical cell) gives rise to the
embryo.
• The basal cell forms closest to the micropyle
and gives rise to the suspensor..

30. Dicot Embryo..
Epicotyl

31. Dicot embryo
• A dicot consists of an embryonal axis and two
cotyledons.
• The portion of embryonal axis above the level of
cotyledons is the epicotyl.
• Epicotyl terminates with the plumule or stem
tip.

32. Dicot embryo
• The cylindrical portion below the level of
cotyledons is hypocotyl ..
• Hypocotyl terminates at its lower end in the
radicle or root tip.
• The root tip is covered with a root cap.

33. Monocot embryo
L.S. of an embryo of grass
L.S: Longitudinal section

34. Monocot embryo
• Embryos of monocotyledons possess only one
cotyledon.
• In the grass family the cotyledon is called
scutellum..
• That is situated towards one side (lateral) of the
embryonal axis.

35. • At its lower end, the embryonal axis has the
radical and root cap.
• The radical enclosed in an undifferentiated
sheath called coleorrhiza.

36. • The portion of the embryonal axis above the level
of attachment of scutellum is the epicotyl.
• Epicotyl has a shoot apex and a few leaf
primordia enclosed in the coleoptile.
Leaf primordia are groups of cells that
will form into new leaves

37. Epiblast:
• The Epiblast is the immature parts of the embryo.
• Epiblast reduced second cotyledon of monocot
embryo..

38. Dr. HarinathaReddy Aswartha
Assistant professor
Department of Microbiology
biohari14@gmail.com