Question

Double fertilization is
A. Fusion of two male gametes with one egg
B. Fusion of two male gametes of a pollen tube with two different eggs
C. Syngamy and triple fusion
D. Fusion of one male gamete with polar nuclei

Answer 1

Hint: Double fertilization may be a complex fertilization mechanism of flowering plants (angiosperms). It begins when a pollen grain adheres to the stigma of the carpel, the feminine plant organ of a flower.

Complete answer:
To answer this question we need to discuss double fertilization in detail.

Double fertilization is a complex fertilization trait of flowering plants (angiosperms). During this one female gamete unites with two male gametes. One amongst the male gametes fertilizes the egg leading to the formation of a zygote and also the other unites with 2 polar nuclei for the formation of an endosperm. This process involves the joining of a female gametophyte, also called the embryo sac with two male gametes (sperm).

The pollen grain adheres to the stigma of the carpel, takes in moisture and begins to germinate, forming a plant structure that extends down toward the ovary through the design.
The tip of the plant structure then enters the ovary and penetrates through the micropyle opening within the ovule. The plant structure proceeds to release the 2 sperm within the megagametophyte.
The cells of an unfertilized ovule are 8 in number and arranged as 3 antipodal cells, 2 polar central cells, 2 synergids & 1 gamete.
One sperm fertilizes the gamete and therefore the other sperm combines with the 2 polar nuclei of the massive central cell of the megagametophyte.
The haploid sperm and haploid egg combine to make a diploid zygote, the method being called syngamy, while the opposite sperm and therefore the two haploid polar nuclei of the massive central cell of the megagametophyte form a triploid nucleus (triple fusion). Some plants may form polyploid nuclei.
The massive cell of the gametophyte will then turn into the endosperm, which provides nourishment to the developing embryo.
Since endosperm is a product of the fusion of three haploid nuclei, it's called triple fusion.
The ovary, surrounding the ovules, develops into the fruit, which protects the seeds and should function to disperse them.

So, the correct answer is option c, syngamy and triple fusion.

Note: The significance of double fertilization:
> Two products are obtained as a result of double fertilization.
> There are chances of polyembryony, and also the plant has better chances of survival.
> It increases the viability of the seeds of angiosperms.
> It utilizes both the male gametes produced by the pollen grains.
> It provides stimulus to plants leading to the ovarian development to fruits and development of ovules into the seed. When the haploid male gametes and feminine gametes fuse, the diploid state of the plant is restored.

Also, double fertilization is absent in gymnosperms as they're innocent of ovaries, and also the male and feminine gametophytes are present on cones. Whereas, in angiosperms, the gametophytes are a component of the flower. Hence, pollination in gymnosperms occurs with the assistance of wind that blows the pollen to land on the feminine cones.