(a) Name the organic material which makes up exine of the pollen grain. 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? [3]

(a) The hard outer layer called exine is made up of sporopollenin which is one of the most resistant organic material. [0.5]

• It can withstand high temperature
• It is resistant to strong acids
• It is resistant to strong alkali
• It is resistant to enzymes [1/2] (any one can be written)

(b) Exine does not form a continuous layer around the pollen grain as it has germ pores through which the pollen tube emerges. [1]

(c) Pollen grains are stored in pollen banks for future use such as in plant breeding programs and also biochemical and physiochemical studies. [1]