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

What type of growth is observed in the pollen tube?

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

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

In wheat and rice,pollen grains lose viability within $30$ minutes of their release. In members of the families Rosaceae,Leguminosae,and Solanaceae,the viability is maintained for $...$.

Pollen grains of some plants germinate on the stigma soon,but they burst in water or a dilute sugar solution. Why?