Vines that crawl up the side of a house are showing thigmotropism. A plant growth in a response to a stimulus is called a tropism. There are different types of tropism. Phototropism (Greek: photos = light) is plant growth in a response to light. Geotropism (Greek: geos = earth) is plant growth in a response to gravity. Hydrotropism (Greek: hydros = water) is plant growth in a response to water. Thigmotropism (Greek: thygmos = touch) is plant growth in a response to contact.