The pulvinus in 'Touch-me-not plant' plays an important role in

The correct option is C Leaf movement
The leaves close under various other stimuli, such as touching, warming, blowing, or shaking. ... The stimulus can also be transmitted to neighboring leaves. It is not known exactly why Mimosa pudica evolved this trait, but many scientists think that the plant uses its ability to shrink as a defense from herbivores. So, the correct option is "C" (Leaf movement).