Tendril of white Bryony, Bryonia dioica. The picture shows a coiled tendril of the hedgerow plant, B. dioica, which had been in place for several days when the picture was made. The process started with the tip of the tendril touching a short twiggy outgrowth on the stem of an Escallonia bush. The tip responded by winding itself around the twig three times within less than a hour ( below top, centre). In subsequent days the lower part of the tendril reacted to produce the coiled spring-like structure below.The response to touch is called thigmotropism. Its mechanism is uncertain, but involves slowing the growth of the side of the tendril that contacts a support, and acclerating growth on the diametrically opposite side. The result is a firm anchor for the plant as it climbs, but one which is also able to stretch in response to movement -due to wind for example - without breaking.