In wheat and rice, how long does the pollen grain remain viable after being released?

Given below are two statements: One is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A) :$ Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.
Reason $(R):$ Presence of more than one nucleus in the tapetum increases the efficiency of nourishing the developing microspore mother cells.
In light of the above statements,choose the most appropriate answer from the options given below:

The enzyme callase,which degrades the callose wall of the microspore tetrad to release four microspores,is provided by the:

Which of the following structures contains the microsporangia?

What are the gametes of angiosperms like?

In angiosperms,male gametes are formed from