Which element is responsible for the germination of pollen grains?

$A$: Initial growth of the pollen tube takes place at the expense of food present in the stigma and style.
$R$: The pollen tube travels intracellularly and chemotactically.

When the pollen tube enters the ovule through the micropyle,it is termed as:

The movement of the pollen tube is called:

Through which path does the pollen tube enter the ovule?

What is the function of filiform apparatus?