Question

Describe double fertilization in angiosperm.

Answer 1

Hint: The fusion of one sperm cell with the egg cell to form the embryo and of the other sperm with the polar nucleus to give rise to the endosperm is referred to as double fertilization. It was first discovered by scientist Nawaschin.

Complete step by step answer:
-Double fertilization is a complex fertilization mechanism that is seen in flowering plants i.e. angiosperms.
-This process involves the fusion of a female gametophyte or megagametophyte, also known as the embryo sac, with two male gametes or sperm.
-The process begins when a pollen grain follows the stigma of the carpel and reaches to the female reproductive structure of a flower.
-Then the pollen grain takes moisture and begins to germinate and forms a pollen tube that encompasses down toward the ovary through the style.
then the tip of the pollen tube enters the ovary and enters through the micropyle opening present in the ovule. The pollen tube allows the release of two sperm in the megagametophyte.
-The cells of an unfertilized ovule have 8 in numbers of cells that are arranged in the form of 3+2+3, mentioning from top to bottom, 3 antipodal cells, 2 polar central cells, 2 synergids and 1 egg cells.
-One sperm fertilizes the egg cell and the other sperm combines with the two polar nuclei that are present on the large central cell of the megagametophyte.
The haploid sperm and haploid egg combine to form a diploid zygote – the process called syngamy.
-The other sperm and the two haploid polar nuclei of the large central cell that is present on the megagametophyte form a triploid nucleus – a process is called triple fusion.
-Syngamy and triple fusion together known as double fertilization.
Endosperm is developed from a large cell of the gametophyte and is a nutrient-rich tissue that helps to provide nutrients to the developing embryo.
-The ovary that surrounds the ovules helps to develop the fruit and protects the seeds.

Note:
The study was made on the Arabidopsis thaliana plant. It was evident that the migration of male nuclei inside the female gamete results in the fusion with the male and female nuclei. This study has been documented by using the in vivo imaging method.