Question

In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of egg apparatus.

Answer 1

Following compatible pollination, the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores. The contents of the pollen grain (2 mole nuclei) move into the pollen tube. Pollen tube grows through the tissues of the stigma and reaches the ovary. After reaching the ovary, pollen tube, enters the ovule through the micropyle and then enters the embryo sac by passing into one of the synergids through the filiform apparatus. It leads to the degeneration of that synergid.

The pollen tube breaks to release its contents (2 male nuclel). Out of the two male gametes one fuses with egg and the other fuses with central cell and fertilise.

Longitudinal section of a flower showing growth of pollen tube

The component cells of the egg-apparatus in an embryo sac include, two synergids one egg cell and the filiform apparatus.

A diagrammatic representation of the mature embryo sac