Question

Apomictic embryos in citrus arise from?

Answer 1

Apomixis is a unique mechanism that produces seeds but without fertilization. There will be no reduction division involved in apomictic embryos. It is a form of asexual reproduction that imitates the sexual reproduction.

Complete answer:
Apomixis is a unique mechanism in terms of its seed formation without fertilization. It is so because it is a form of asexual reproduction but actually it imitates sexual reproduction. So in Apomixis the seed is formed without meiosis and the syngamy. Meiosis is a division that makes the chromosome number half, so it is essential for the organism that reproduces through sexual reproduction and syngamy is the fusion that takes place between the gametes(formed by meiosis) to form the zygote. This does not take place in Apomixis as the pollen that is the male part is not involved in this process. So basically in Apomixis the maternal cells that are diploid in nature like antipodal nucellus form an embryo but without meiosis and syngamy (that is without fertilization).
In case of citrus the embryos are formed by maternal sporophytic tissue from nucellar cells and integuments in the ovule that are the diploid cells and then, the ovule contains many embryos and it is known as polyembryony. This kind of embryony that is found in citrus is called Adventive type of embryony.

So, Apomictic embryos in citrus arise from the maternal sporophytic tissues present in the ovule that contain diploid cells and are formed without fertilization consisting of many embryos in it.

Note:
The production of seeds without fertilization is very important topic for scientists as it can help the farmers to get seed in very low prices as the apomictic hybrid seeds can be used in place of high priced – hybrid seeds, because the apomictic seeds does not segregate from its characters so they are genetically similar as it is a form of asexual reproduction.