sexual reproduction in plants

pollen formation

1. Diploid microspore mother cells in the anther undergo meiosis. They form four haploid microspores.

2. Haploid microspores undergo mitosis to mature into pollen grains. Pollen grains consist of two nuclei – the generative nucleus and the pollen tube nucleus – and a protective coating

ovum formation

1. Diploid megaspore mother cells in the ovule undergo mitosis, forming an ootid and three polar bodies which degenerate and are reabsorbed.

2. The ootid undergoes three mitotic divisions to form an embryo sac. The embryo sac contains two polar nuclei (form the endosperm), an egg cell (forms the zygote), two synergids (help the generative nucleus reach the egg cell) and three antipodal cells (no established function) with a protective coating.

fertilisation in plants process

● Pollen grain composed of the pollen tube nucleus and the generative nucleus adheres to the stigma, where it subsequently germinates.

● The pollen tube grows down the style via the secretion of digestive enzymes which digest the surrounding tissue and use it as a source of nutrients.

● The pollen tube grows through the micropyle into the embryo sac.

● The generative nucleus of the pollen divides by mitosis to produce two sperm cells which enter the embryo sac.

double fertilisation process

● Double fertilisation occurs: one of the male gametes fuses with the female nucleus to form a diploid zygote and the other male gamete fuses with two polar nuclei to form a triploid endosperm nucleus which serves as a source of nutrients for the embryo