Question

Fusion of a male gamete with egg in the embryo sac is
(a) Autogamy
(b) Syngamy
(c) Double Fertilization
(d) Triple Fusion

Answer 1

Hint: The sperm will fertilize an egg cell and the second sperm will fuse with a single nucleus present in the megagametophyte. Two sperm cells are involved with double fertilization; one fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei that form the endosperm.

Complete Step by Step Answer:
Syngamy and triple fusion are the two main events of sexual reproduction in plants. Syngamy is the fusion of one of the male gametes with the egg cell to produce a zygote while In triple fusion, the second male gamete fuses with two polar nuclei to produce the primary endosperm nucleus.
Since two types of fusions, that is, syngamy and triple fusion take place in an embryo sac the phenomenon is termed double Fertilisation.

So, the correct answer is, ‘Syngamy.’

Additional Information:
Double fertilization process:
Double fertilization is a complex process involved in the fertilization of flowers (angiosperms). This process involves the joining of two male gametes (sperm) with a female gametophyte (megagametophyte, also called the embryo sac) . It starts when a grain of pollen adheres to the carpel stigma, the female reproductive structure of a flower. The pollen grain takes moisturizer and begins to germinate, forming a tube of pollen which extends down through the style towards the ovary. The tip of the pollen tube then reaches the ovary, passing through the opening of the micropyle in the ovule. The pollen tube in the megagametophyte produces the two sperms. An unfertilized ovule's cells are 8 in number and arranged in the form of 3 + 2 + 3 (from top to bottom) i.e. 3 antipodal cells, 2 central polar cells, 2 synergies & 1 egg cell. One sperm fertilizes the egg cell and the other sperm blends with the two polar nuclei of the megagametophyte's large central cell. The haploid sperm and haploid egg unite to create a diploid zygote, the process being called syngamy, while the other sperm and the two haploid polar nuclei create a triploid nucleus (triple fusion) of the megagametophyte's large central cell. Some plants may form polyploid nuclei. Some plants can form polyploid nuclei. The gametophyte's large cell will then grow into the endosperm, a nutrient-rich tissue which provides the developing embryo with nourishment. The ovary, which surrounds the ovules, develops into the fruit which protects the seed and can disperse it. The two central cell maternal nuclei (polar nuclei) , which contribute to the endosperm, arise from the same single meiotic product which gave rise to the egg by mitosis. The maternal contribution of the triploid endosperm to the genetic makeup is double that of the embryo.

Note: The main purpose of the endosperm in the seed is to provide nutrients to the growing embryo. The endosperm is tissue present in many dicots and all monocot seeds for storage. All dicot seeds have an endosperm formed during seed evolution. The endosperm is however used up during growth in some species and these dicot seeds store food reserves in their large cotyledons.