1.The process of fusion of male gamete with the female gamete to form the diploid zygote (2n) is known as fertilisation. The fusion of one male gamete with egg and that of another male gamete with a secondary nucleus is called double fertilisation.
2.It is the characteristic feature of only angiosperms. All angiosperms are characterised by a unique process called double fertilisation. Double fertilisation is significant because it involves the use of both the male gametes produced by a pollen grain.
3.This avoids the chances of polyembryony and increases the chances of survival of the future plant. It consists of two fusions and results in the formation of two products. First fertilisation restores diploidy in the life cycle.
4.The diploid zygote develops into an embryo which subsequently develops into a new plant. Second fertilisation product, triploid PEN (Primary endosperm nucleus) develops to form a nutritive tissue called endosperm for developing an embryo.
5.The significance of double fertilisation:
(a) Syngamy results in formation of zygote which gives rise to the embryo
(b) Double fertilisation results in the formation of triploid endosperm which ensures, better nourishment of the developing embryo.
(c) Seeds are viable with a high percentage of germination.
(d) Double fertilisation brings about the recombination of characters.
6.Male gametophyte produces two male gametes in angiosperms, out of them one unites with the female gamete and the other unites with the secondary nucleus. It is called double fertilisation as both gametes take part in fertilisation and fertilisation occurs twice.
7.During double fertilisation, pollen tube with two male gametes and tube nucleus enters the embryo sac on reaching the ovule, through the micropylar end. After this, the tip of pollen tube bursts and two male gametes are discharged.
8.Out of these two male gametes, one unites with the egg of female and the other unites with the secondary nucleus of the embryo sac, forming triploid or triple fusion nucleus, called the primary endosperm nucleus.
9.The other male gamete fuses with the egg nucleus causing fertilisation, resulting in the formation of a diploid zygote or diploid oospore. This is called syngamy.
10. The process involving the fusion of haploid nucleus of male gamete with the diploid secondary nucleus to form a triploid primary endosperm nucleus is called triple fusion.
Answers & Comments
1.The process of fusion of male gamete with the female gamete to form the diploid zygote (2n) is known as fertilisation. The fusion of one male gamete with egg and that of another male gamete with a secondary nucleus is called double fertilisation.
2.It is the characteristic feature of only angiosperms. All angiosperms are characterised by a unique process called double fertilisation. Double fertilisation is significant because it involves the use of both the male gametes produced by a pollen grain.
3.This avoids the chances of polyembryony and increases the chances of survival of the future plant. It consists of two fusions and results in the formation of two products. First fertilisation restores diploidy in the life cycle.
4.The diploid zygote develops into an embryo which subsequently develops into a new plant. Second fertilisation product, triploid PEN (Primary endosperm nucleus) develops to form a nutritive tissue called endosperm for developing an embryo.
5.The significance of double fertilisation:
(a) Syngamy results in formation of zygote which gives rise to the embryo
(b) Double fertilisation results in the formation of triploid endosperm which ensures, better nourishment of the developing embryo.
(c) Seeds are viable with a high percentage of germination.
(d) Double fertilisation brings about the recombination of characters.
6.Male gametophyte produces two male gametes in angiosperms, out of them one unites with the female gamete and the other unites with the secondary nucleus. It is called double fertilisation as both gametes take part in fertilisation and fertilisation occurs twice.
7.During double fertilisation, pollen tube with two male gametes and tube nucleus enters the embryo sac on reaching the ovule, through the micropylar end. After this, the tip of pollen tube bursts and two male gametes are discharged.
8.Out of these two male gametes, one unites with the egg of female and the other unites with the secondary nucleus of the embryo sac, forming triploid or triple fusion nucleus, called the primary endosperm nucleus.
9.The other male gamete fuses with the egg nucleus causing fertilisation, resulting in the formation of a diploid zygote or diploid oospore. This is called syngamy.
10. The process involving the fusion of haploid nucleus of male gamete with the diploid secondary nucleus to form a triploid primary endosperm nucleus is called triple fusion.