Which of the following plant product is the hardest in nature?
Sporopollenin
Sporopollenin is a polymer, tougher than lignin. It mainly contains carotenoids which make spores and pollen grains of plants resistant to biodegradation.
Lignin is the main component of secondary walls and wood of plants. It is composed of phenylpropanoid units.
Cutin is a transparent waxy substance forming the cuticle of plants.
Suberin is a wax-like fatty substance found in the cell wall of cork cells.