Double fertilization is a complex fertilization mechanism that has evolved in flowering plants, known as angiosperms. This process involves the joining of a female gametophyte (embryo sac) with two male gametes (sperm). It begins when a pollen grain adheres to the stigma of thecarpel, the female reproductive structure of a flower. After a pollen grain has landed on an accessible stigma, the pollen grain takes in moisture and begins to germinate, forming a pollen tube that extends down toward the ovary through the style. The tip of the pollen tube then enters the ovary and penetrates through the micropyle. The micropyle is an opening in the protective layers of the ovule. The pollen tube proceeds to release the two sperm in or near the embryo sac.
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incomplete. who will tell after it
then one of the male gamete fuses with the ovum or the egg and form seed.
the second moves upward and their fuses wih the polar nuclei to form the endospremic cell which later develops into endosperm.
polar nuclei: Two haploid nuclei in the centre of the embryo sac of flowering plants. These nuclei fuse with a male gamete nucleus to form a triploid endosperm nucleus, which subsequently divides to form the endosperm.
another short and good defination:
double fertilization: A process, unique to flowering plants, in which two male gamete nuclei, which have travelled down the pollen tube, separately fuse with different female nuclei in the embryo sac. The first male nucleus fuses with the egg cell to form the zygote; the second male nucleus fuses with the two polar nuclei to form a triploid nucleus that develops into the endosperm.
hope this helps. plz give thumbs up.
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i think we can make it a bit more simple like this
in flowering plants the fertilization is called double fertilization bcoz fertilization occurs twice. on entering the ovary the pollen tube releases 2 male gametes .in the first reaction , one of the male gametes fuses with eggcell and forms the zygote . this reaction is a diploid reaction and is also called syngamy.
in the second reaction the second male gamete fuses with the 2 polar nuclei and form the product called P.E.N - primary endosperm nucleus. this reaction is called the triploid reaction or the triple fission.
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Double fertilization in flowering plants involves the fusion of two sperm cell nuclei of the male gametophyte with two cell nuclei of female gametophyte. One sperm fuses with the haploid egg cell to form the zygote; the other sperm unites with the diploid central cell to form a triploid cell that will develop to an endosperm.
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The two central cell maternal nuclei (polar nuclei) that contribute to the endosperm arise by mitosis from a single meiotic product. Therefore, maternal contribution to the genetic constitution of the triploid endosperm is different from that of the embryo.
Recently research has shown that in one primitive group of flowering plants, the water lilies, Nuphar, the endosperm is diploid, resulting from the fusion of a pollen nucleus with one, rather than two, maternal nuclei.
In gymnosperms, such as conifers, the food storage tissue is part of the female gametophyte only, a haploid (1n) tissue, so there is no double fertilisation.
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