Test: Double Fertilisation, Post Fertilisation: Structures And Events

• Endosperm is formed when the two sperm nuclei inside a pollen grain reach the interior of an embryo sac or female gametophyte.
• One sperm nucleus fertilizes the egg, forming a zygote, while the other sperm nucleus usually fuses with the two polar nuclei or the secondary nuclei at the center of the embryo sac, forming a primary endosperm cell (often called as the triple fusion nucleus).
• The cell created in the process of double fertilization develops into the endosperm. 

It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein.

Synergids or synergid cells: haploid accessory cells at the micropylar pole of the angiosperm embryo sac; glandular-like cells involved in pollen tube attraction and reception.

Megapore is a haploid structure which divides and gives rise to embryo sac which is also called as female gametophyte. Eight-nucleate embryo sacs may be monosporic (e.g.. Polygonum); or bisporic (e.g., Allium); or tetrasporic (e.g., Adoxa).

Endosperm is formed during the double fertilization . It is triploid because it is formed when one of the two sperm that is haploid enters inside the embryo sac & fuses with two polar nuclei (each polar nuclei is haploid). So the endosperm formed is triploid.

Endosperm: Endosperm development precedes embryo development. The primary endosperm cell divides repeatedly and forms a triploid endosperm tissue. The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo.

Aleurone is a protein found in protein granules of maturing seeds and tubers. It also describes one of the two major cell types of the endosperm, the aleurone layer. It is the outermost layer of the endosperm.

Fertilization: The pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule.

The pollen tubes enter the embryo-sac where two male gametes are discharged. One of the male gametes fuses with the egg cell (syngamy) and forms a diploid zygote. The other male gamete fuses with the diploid secondary nucleus to four primary endosperm nucleus (PEN), which is triploid in nature.

Since, two types of fusion. syngamy and triple fusion takes place in the embryo sac. the process is known as double fertilisation. 

In pea, endosperm is consumed by developing embryo in the seed. The endosperm is completely absorbed by the growing embryo and the food reserve gets stored in the cotyledons. Such seeds are called non endospermic or exalbuminous.

Parthenocarpy (Gk. parthenos-virgin; karpos-fruit) is the formation of seed less fruits without fertilization. The fruits developed from unfertilized ovary are called parthenocarpic fruits. Other options are incorrect because
(i) In asexual reproduction, a single individual (parent) is capable of producing offspring.
(ii) For apomixis and sexual reproduction. 

The fusion of one male gamete with the egg cell is called syngamy or true fertilization while the fusion of second male gamete with two polar nuclei is called triple fusion. Syngamy along with the triple fusion is called double fertilization. Double fertilization is a characteristic feature of flowering plants or angiosperms.