Scientists unwind the secrets of climbing plants’ tendrils

In the search for precious sunlight, instead of growing sturdy trunks to reach towards the light, climbing plants such as honeysuckle and grapevines cling to their surroundings and then heave themselves upwards. Scientists have now cracked how some plants do this, and in the process they have created a new kind of spring.

Climbing plants have been puzzling biologists since the 19th century – including Charles Darwin. The technique the plants use to winch themselves upwards is well known, but the underlying mechanism has been a mystery until now.

The new research, published in the journal Science, investigates in unprecedented detail the supporting tendrils of the cucumber plant. When first formed, a tendril is almost straight, and while growing it slowly waves around in a poorly understood process called circumnutation. When it encounters a foothold, the end of the tendril wraps around it, securing a support.

The tendril then shortens by coiling up into a corkscrew-like helix, pulling up the rest of the plant. But rather than twisting only in one direction – impossible without twisting the plant at the other end – the two halves of the coiled section curl up in opposite directions, separated by an uncoiled stretch called a perversion, so there’s no net twist. How this coiling occurs wasn’t understood.

A group of scientists led by Sharon Gerbode and Josh Puzey, who carried out the work while at Harvard University, investigated the nature of recently discovered specialised cells that form a stiff ribbon of material inside each soft, fleshy tendril.

This ribbon controls a tendril’s shape, and the team suspected that to coil, cells on one side of the ribbon are stiffened and shortened more than those on the other side, causing a turn towards the stiffened side.