One pollen mother cell may produce four germinating pollen grains, each with two male nuclei and one tube nucleus. How many meiotic divisions are necessary to bring this about

In a pollen grain, larger nucleus is

The function of endothecium is

Mature male gametophyte is derived from a 'pollen mother cell' by

After penetrating stigmatic and styler tissues, the pollen tube usually grow down towards the egg because

Exine of pollen grains is composed of