→The period for which pollen grains remain viable is 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 Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.
→Once they are shed, pollen grains have to land on the stigma before they lose viability if they have to bring about fertilisation.