Apomixis in Flowering Plants:
Apomixis is a sexual mode of reproduction in which new individuals are formed without the formation of gametes and their fusion.
Types of Apomixis:
Maheshwari used the following simple classification of apomixis in flowering plants:
1. Nonrecurrent Apomixis:
In this type of apomixis, “the megaspore mother cell undergoes the usual meiotic divisions and a haploid embryo sac is formed. The new embryo may then arise either from the egg or from some other cell of the gametophyte”. The haploid plants have half as many chromosomes as the mother plants and “the process isn’t repeated from one generation to another”, so that’s why it is called non-recurrent apomixis.
2. Recurrent Apomixis:
In this type of apomixis, the megagametophyte has the same number of chromosomes as the mother plant because meiosis was not completed. It generally arises either from an archesporial cell or from some other part of the nucellus.
3. Adventive Apomixis:
There may be a megagametophyte in the ovule, but the embryos don’t arise from the cells of the gametophyte. They arise from cells of the nucellus or the integument. Adventive apomixis is important in several species of Citrus, Garcinia, Euphorbia dulcis, Mangifera indica, etc.