Question

Why is fertilization in an angiosperm referred to as double fertilization? Mention the ploidy of the cells involved.
Draw a neat labeled sketch of L. S. of an endospermic monocot seed.

Answer 1

Hint: Double fertilization means two sperm is fusing two different eggs or one egg and one polar cell. It is a specialized character of monocot.
It produces an embryo with a 2n number of chromosomes and an endosperm with 3n number of chromosomes where n is the haploid number of chromosomes.

Complete answer: Double fertilization in angiosperm: Double fertilization is a characteristic feature of flowering plants or angiosperms.
In the double fertilization process, one of the two pollen nuclei (sperms) fuses with an egg, and another egg fuses with polar nuclei.
The process of fusion of sperm with egg to form an embryo is called syngamy and the process of fusion of sperm with polar nuclei to form endosperm is called triple fusion.
Hence, there are two types of fusion seen – one is fertilization and another is triple fusion.
Thus, fertilization of an angiosperm is called double fertilization.

Name of the cells and its ploidy are:
1. Egg cell – haploid.
2. Both pollen nuclei – haploid.
3. Polar nuclei – haploid.
4. Zygote – diploid.
5. Endosperm – triploid.

Note: The embryo of monocot seed helps to develop fruit and the endosperm provides nutrition to the growing embryo of monocot plant. It also protects the embryo and controls the embryonic growth as it acts as a mechanical barrier during seed development and germination process.