Class 12th Biology 2016 Set1 Outside Delhi Board Paper Solution
(a) Name the organic material exine of the pollen grain is made up of. How is this material advantageous to pollen grain ?
(b) Still it is observed that it does not form a continuous layer around the pollen grain. Give reason.
(c) How are ‘pollen banks’ useful ?
(a) The hard outer layer called exine is made up of sporopollenin which is one of the most resistant organic material. It can withstand high temperature, strong acids and alkalis. It cannot be degraded by any of the known enzymes. Hence, it acts as a shield and protects the pollen grain from getting damaged.
(b) Exine does not form a continuous layer around the pollen grain. Pollen grain exine has prominent aperture called germ pore where sporopollenin is absent. Germ pores serve as an oudet for the formation of pollen tube.
(c) Pollen grains at a large can be stored for years in liquid nitrogen (— 196°C). So, after this treatment they are stored in pollen banks. Such conserved pollen grains can be used in plant breeding programs.
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