Seminar on double fertilization and development of embryo
Presented by :- mohd abdullah haidery
m.Sc – 1 sem (1)
Department of botany
Sant gadge baba amravati university
Structure of flower
Development of male gametophyte
Development of female gametophyte
Fertilization i.e. double fertilization
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.
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.
Porogamy:- Here the
entry of the pollen tube into
the ovule takes place
through the micropyle.
like Casuarina, the entry of
pollen tube takes place
through the chalaza.
Cucurbita, pollen tube entersEntry of pollen tube in the ovule; A.
Porogamy, B. Chalazogamy, C.
the ovule through the
Irrespective of the place of entry into ovule the
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
between the two synergids without destroying
either of them or
directly penetrate one of the synergids .
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 .
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