In which cell's cytoplasm are both male gametes first released?

What acts as a mediator in the pollen-pistil interaction?

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 the egg apparatus.

Identify the correct order of events in pollen-pistil interaction from the options given below.
$I.$ Release of male gametes into the embryo sac
$II.$ Deposition of pollen grains on stigma
$III.$ Entry of pollen tube into embryo sac
$IV.$ Development of pollen tube
$V.$ Entry of pollen tube into the ovule

Which of the following stimulates pollen germination and pollen tube growth?

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