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Seminar on double fertilization and development of embryo

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Double fertilization
by
Mohd Abdullah Haidery

Seminar on double fertilization and development of embryo

  1. 1. Presented by :- mohd abdullah haidery m.Sc – 1 sem (1) Department of botany Sant gadge baba amravati university amravati
  2. 2. CONTENTS:Introduction Structure of flower Development of male gametophyte Development of female gametophyte Pollination Fertilization i.e. double fertilization References
  3. 3. The formation of megaspores inside the ovules of seed plants. A diploid cell in the ovule, called a megasporocyte or a megaspore mother cell, undergoes meiosis and gives rise to four haploid megaspores. In most plants, only one of the megaspores then goes on to develop into a mega gametophyte within the ovule, while the other three disintegrate. In the ovules of angiosperms, megasporogenesis takes place within a structure called a nucellus, and it is the megaspore farthest from the micropyle of the ovary that survives.
  4. 4.  Self pollination  Cross pollination
  5. 5. When the pollen grain is shed from the anther it has two cells a generative cell and a tube cell . The generative cell give rise to male two male gametes. The pollen tube with two male gametes grows down through the style and enters into the ovule usually through the micropyle. It releases two male gametes into the embryo sac. One fuses with the egg and forms zygote. This fusion of male and female gamete is known as fertilization. The second male nuclei fuses with the two polar nuclei which form endosperm. So there is two fertilization usually called as double fertilization or triple fusion.
  6. 6. Porogamy:- Here the entry of the pollen tube into the ovule takes place through the micropyle. Chalazogamy:-In plants like Casuarina, the entry of pollen tube takes place through the chalaza. Mesogamy:- In Cucurbita, pollen tube entersEntry of pollen tube in the ovule; A. Porogamy, B. Chalazogamy, C. the ovule through the Mesogamy integuments.
  7. 7. Irrespective of the place of entry into ovule the pollen tube always enter the embryo sac through the micropylar region . It may enter the embryo sac i.e. one of the following routes  between the egg cell and the synergids without destroying the latter  between the wall of the embryo sac or both the synergids  between the two synergids without destroying either of them or  directly penetrate one of the synergids .
  8. 8.  The content of pollen tube are released and the egg cell and synergids are in close contact sperm do not have to transfer long.  The sperm show amoeboid movement one of the male gamete moves towards the egg and the other to the polar nuclei .  The factor or forces which propel one of the sperm into the egg and the other in the central cell with remarkable regularity and precision are not properly known .one of the two sperm fuses with the egg the receptiveness of the egg is lost once a sperm has fuse with it .
  9. 9. B.P.Pandey(1992) “Text book of Angiosperm & Embryology” S. chand publishing house, New Delhi-110002. P.Maheshwari,(1990) “ An introduction to the embryology of angiosperms” East west press , New Delhi Bhojwani and Bhatnagar S.P (2000), “ the embryology of angiosperms” Vikas publishing house, New Delhi  http://en.wikipedia.org

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