Plants respond to their environment to survive. Thigmotropism is plants response to touch. An example is modified leaves called tendrils which rap around things or other plants for support. Plants like grapes, beans, and cucumbers have tendrils.

Plant with tendrils attached to a string.

Plant with tendrils exhibiting thigmotropism
Photo by: Maria Keays, 

The tendril swings around until it senses something to wrap around. When they do touch something the side of the plant that is sensing the touch sends the plant hormone auxin to the other side. Auxin elongates plant cells. The side not touching the the object elongates. This difference in growth forms a spiral (seen above). Another example of plants responding to touch is Thigmomorphogenesis, plants changing their growth pattern in response to touch.
Hope you learned something new!

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