The answer is D- thigmotropism Tropism is plant growth in a response to a stimulus. Through the process of elimination:A - phototropism is plant growth in a response to light. B - Photoperiodism is an organism reaction to the lengths of days and nights. C - Gravitropism is plant growth in a response to gravity.D - Thigmotropism is plant growth in a response to contact Since a grapevine makes a contact with a fence, this is an example of thigmotropism.