(a) Do all pollen grains remain viable for the same length of time ? Support your answer with two suitable examples.
(b) How are pollen grains stored in plooens banks ? State the purpose of storing pollen grains in these banks

Explanation

(a) No, all pollen grains do not remain viable for the same length of time. They are highly variable and to some extent, depends on the prevailing temperature and humidity.
In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosacea, Leguminoseae and Solance they maintain viability for months.
(b) To store pollen grains of large no. of species for years =, in liquid nitrogen `(-196^(@))`, Such stored pollen are used as pollen banks.
The purpose of storing pollen grains in thses banks is that can be used in plant breeding programs.