In plants, reproduction is attained by fertilization; more precisely double fertilization.
Double Fertilization Definition
“Double fertilization is a complex process
which involves the fusion of one female gametophyte with two male gametes.
Double fertilization is a chief trait of
flowering plants. In the phenomena, one female gamete unites with two male
gametes. One of the male gametes fertilizes the egg resulting in the formation
of a zygote and the other unites with 2 polar nuclei for the formation of an
endosperm.
Double fertilization provides stimulus to
the plant resulting in the ovarian development to fruits and development of
ovules into the seed. When the haploid male gametes and female gametes fuse,
the diploid state of the plant is restored.
Double Fertilization
in Angiosperms
Angiosperms are flower-bearing plants and
are the most diverse group of terrestrial plants. The flowers form the
reproductive part of angiosperms with separate male and female reproductive
organs. Each contains gametes – sperm and egg cells, respectively.
Pollination helps the pollen grains to
reach stigma via style. The two sperm cells enter the ovule-synergid cell. This
proceeds to fertilization.
In angiosperms, fertilization results in
two structures, namely, zygote and endosperm, hence the name “double
fertilization.”
Double fertilization is a complex process
where out of two sperm cells, one fuses with the egg cell and the other fuses
with two polar nuclei which result in a diploid (2n) zygote and a triploid (3n)
primary endosperm nucleus (PEN) respectively.
Since endosperm is a product of the fusion
of three haploid nuclei, it is called triple fusion. Eventually, the primary
endosperm nucleus develops into the primary endosperm cell (PEC) and then into
the endosperm.
The zygote becomes an embryo after numerous
cell divisions
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