What is a pollen grain?

The microspore tetrad of an angiosperm,at the time of formation,is surrounded by a callose wall. The breakdown of this wall is brought about by the enzyme callase,which is synthesized by the:

What do '$c$' and '$d$' represent in the given figure?

The germ pores on the pollen grains are found on the

What is released upon the dehiscence of the anther?

How many microsporangia does a typical angiosperm anther contain?