Roots play an insignificant role in the absorption of water in the case of Triticum, Pisum, Pistia, Helianthus.

Roots play an insignificant role in the absorption of water in the case of pistia. Pistia is a hydrophytic (aquatic) plant. Hydrophytes are the plants which grow only in or on water. Pistia glides on the surface of the water and its roots are bent and grown towards under water. Its root is rich with air sacs which enables them to float. Their roots are small, light, feathery in structure and are specialized in taking oxygen, hence water can easily spread and gets into the leaves and also gets enough water to survive. So, the correct answer is option C.