Question

The pollen grains can be stored in viable condition for many years in the following conditions.
A. Anaerobic conditions in (0⁰C )
B. Liquid nitrogen (-196⁰C )
C. Liquid nitrogen (0⁰C)
D. Liquid hydrogen (-196⁰C)

Answer 1

Hint:-Pollen grains are male gametophytes. Pollen grains fuse with egg and form zygote. When once they are shed, pollen grains have to land on stigma before they lose viability. They can lose their viability within 30 minutes. Cryopreservation is the important method of preservation for a longer time. Liquid nitrogen at a certain temperature(below 0⁰C) is good for preservation. Pollen seed banks are made which is useful in crop breeding programmers.

Complete answer:
Flowers can be unisexual and bisexual depending on the presence of male and female gametophypes. Stamen mainly contains two parts, another and filament. Anther is a bilobed structure that consists of microsporangia. Microsporangia develop further and become pollen sacs. Tapetum provides the nourishment to the pollen grains. Microspore tetrads are formed and under meiotic division to form pollen grain.
Pollen grains have two layers exine (outer layer) and intine (inner layer). Exine cannot be degraded even at high temperature and strong acids and alkalis due to the presence of sporopollenin. This layer provides protection to the pollen grains from adverse conditions. It helps to preserve pollen grains and prevents them from getting denatured for a long period of time.
Various crop breeders store pollen grains and maintain their viability by providing specific environments. Pollen grains store at a low temperature. Preserving pollen grains at lower temperature that is (-196⁰C) in liquid nitrogen is known as cryopreservation. Pollen grains are preserved at lower temperature for a longer time by reducing the growth rate of the cells.
From the above information, we have reached the conclusion that pollen grains can be stored in a viable condition for many years in the liquid nitrogen at -196⁰C.
So the correct answer is option (B).

Note:-
Various methods of preservation are drying, refrigeration and fermentation. Canning, pasteurization, freezing, irradiation and chemicals are some modern methods of preservation. Degradation of substance can be due to temperature, microbes or any other source. Preservation at low temperature is the most effective method as it does not allow the microbes to grow and preserve the substance from contamination.