Which of the following is the hardest substance in the plant kingdom?

Sporopollenin

The correct answer is Option : (2) Sporopollenin

Sporopollenin is considered the hardest substance in the plant kingdom. It is a highly durable and resistant material that makes up the outer layer of pollen grains and spores.

Sporopollenin is known for its exceptional stability and resistance to various environmental conditions. It can withstand strong acids, high temperatures, enzymes, and other degrading agents, making it highly durable and long-lasting.

Due to its robust nature, sporopollenin helps protect the genetic material inside pollen grains and spores during dispersal and ensures their successful reproduction.

Therefore, sporopollenin is the hardest substance in the plant kingdom.