The movement of the pollen tube is..........

$A$: Filiform apparatus guides the pollen tube into the synergids.
$R$: It is a special cellular thickening at the micropylar tip to secrete chemotropic stimulus.

Through which cell of the embryo sac does the pollen tube enter the embryo sac?

The discoverer of the pollen tube is $........$.

The period of pollen viability depends on which of the following factors?

Which structure guides the entry of the pollen tube into the synergids?