Pollen grains can be stored for years in liquid nitrogen at what temperature?

-196°C

The correct answer is Option (3) → -196°C

When once they are shed, pollen grains have to land on the stigma before they lose viability if they have to bring about fertilisation.  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. It is possible to store pollen grains of a large number of species for years in liquid nitrogen (-196^oC). Such stored pollen can be used as pollen banks, similar to seed banks, in crop breeding programmes.

At such low temperatures, the metabolic activities of the pollen grains are significantly slowed down or halted, preserving their viability over an extended period. The low temperature helps to prevent cellular damage and degradation that would occur under normal conditions.

By storing pollen grains in liquid nitrogen at -196°C, researchers and plant breeders can establish pollen banks, similar to seed banks. These banks serve as repositories of genetic diversity and resources for crop breeding programs. The preserved pollen can be thawed and used in controlled pollination experiments or for artificial insemination in plant breeding efforts.

The extremely low temperature of -196°C provided by liquid nitrogen is crucial for maintaining the viability and genetic integrity of stored pollen grains over long periods, enabling their utilization in various research and breeding applications.