Question

Pollen grains are able to tolerate extremes of temperatures and desiccation because their exine consists of

• A. Callose
  
• B. Sporopollenin
  
• C. Suberin
  
• D. Cutin
  

Answer 1

The correct option is B Sporopollenin


Wall of pollen grain
Wall of pollen grains is made up of two layers as follows:
Exine
Intine


Exine
Exine is the outer layer, composed of an organic compound sporopollenin which smakes it resistant to enzymes, acids, alkalis and high temperatures. It is not present in germ pores, through which the pollen tube emerges during pollen germination.
Intine
Intine is the thin and uniform inner layer, which is composed of pectin and cellulose. It can be easily degraded by enzymes, acids and high temperatures.
Cutin and Suberin
Cutin and suberin are polyesters present in the cell wall of plants for protection. For example, suberin is mainly present in cork and cutin is the major component of the cuticle.
Callose
Callose is another polysaccharide present in plants which provides protection against invasion of pathogens.



Final answer
(c) Sporopollenin