Sexual Reproduction in Flowering Plants Test - 4

One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing syngamy. This results in the formation of a diploid cell, which is the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus. This completes the process of double fertilisation.

Chalazogamy, porogamy and misogamy are the modes of entry of the pollen tube into the embryo sac. Allogamy is when the pollen is transferred from the anther to the stigma of different flowers on different plants.

Exine is thick, sculptured and smooth. It is cuticularised and the cutin is made of a special type called sporopollenin, which is resistant to the chemical and biological decomposition.

The exine is made of two major layers—the outer sexine and the inner nexine. The sexine is further divided into the outer tectum and the inner endosexine. The nexine is made of the inner endexine and the outer foot layer.

Germ pore acts as the region through which the pollen tube enters the ovary so that the pollen and egg may fuse together to form the zygote.

Pollen grains in angiosperms are released at the 2-celled stage—generative cell and vegetative cell. The generative cell divides to form two male gametes.

In pea seeds, the endosperm is used up. Such seeds are called exalbuminous seeds.

Pollination by insects is called entomophily. Pollination by wind is called anemophily. Pollination by snails is called malacophily.

The egg apparatus consists of one egg cell (haploid female gamete) and two supporting cells called synergids.

Filiform apparatus is contained in synergids which guides the pollen tube to the egg cell.