Botanique.org

Germination of pollen begins when the grain swells because of the absorption of the water at stigma surface. Turgescent vacuoles push the intine and the cytoplasm towards an aperture of the pollen grain of pollen: it is the beginning of the growth of the pollen tube.

When the pollen tube gets longer, the 2 cells (generative cell and tube cell) and the cytoplasm are confined at its extremity, the generative cell being slightly behind the tube cell. Phenomena of cellular strain are limited at the end of the tube.

The pollen tube crosses the style without ever penetrating into cells; cells of the conducting tissue act as rails for the pollen tube that finishes its growth at the level of the micropyle into the ovule.