Apomicitic life cycle: Apogamy, apospory & vegetative apomixis

Apomixis:- When embryo and seed are produced from the parent plant without fertilization, it is called asexual reproduction. Any vegetative cell of the ovule acts as a zygote. The resulting seedlings are clones of their parents. It is of three types -

1. Adventive Embryony

2. Apospory

3. Diplospory

1. Adventive Embryony:- When the embryo develops from a vegetative cell of ovule (integument or nucellus or challaza) without the formation of embryo sac, it is called adventive embryony. Examples:- Lemon, mango etc.

2. Apospory:- When the development of the embryo sac occurs without meiosis from any vegetative cell of ovule (integument or nucellus or challaza), it is called as apospory. It means megaspore is not produced here. Each cell of the embryo sac is diploid. An embryo is developed from any one cell of the embryo sac. Example:- Crepis

3. Diplospory:- When the embryo sac develops from a diploid megaspore, it is called as diplospory. Megaspore is diploid because it is formed by mitosis instead of meiosis. Therefore, each cell in the embryo sac is also diploid.

Embryo development occurs without fertilization. Depending upon the embryo develops from which cell of the embryo sac, there are 2 types of diplospory -

a. Parthenogenesis

b. Apogamy

a. Parthenogenesis:- When the embryo develops from the egg cell, it is called parthenogenesis. As shown in the diagram below. Example:- Taraxacum (grass)

b. Apogamy:- When the embryo develops from the antipodal cell or the synergid, it is called apogamy. As shown in the diagram below. Example:- Onion