Water goes down the drain clockwise in the Northern hemisphere and vines grow in a right-hand direction – right?
Wrong. According to Australian plant scientist Angela Moles, most vines twist anticlockwise.
Ms Moles, an evolutionary biologist at the University of New South Wales, Sydney, was engaged on a massive fact-finding mission about plants across the world, as part of the World Herbivory Project at her Big EcologyLab.
92% of Vines Grow Anticlockwise
Over two years, she travelled to 75 different ecosystems, ranging from arctic tundra at 75 degrees north in Eastern Greenland, to dense tropical rainforests in the Congo, Peru, Panama and China; deserts in Australia and Israel; savannas in South Africa, Australia, and Zambia; temperate forests in America, Sweden and Norway, and all the way down to tundra in southern Patagonia.
She said she “spent an average of about 3 days per ecosystem, and was travelling pretty much nonstop for two years, during which I had no home, and remarkably few possessions”.
While vines were not the principal object of the study tour, she managed to look at 1485 specimens at 17 different sites, and was surprised to find that the majority, 92% in fact, were twisting anticlockwise.
The Coriolis Effect on Climbing Plants
The Coriolis effect is a hypothesis that that water going down a plughole twists clockwise in the Northern hemisphere and anticlockwise in the Southern hemisphere because of the Earth’s rotation.
(However, Ms Moles points out you would need an enormous bathtub hundreds of metres across for this to be demonstrated.)
The rotation is also supposed to affect directions of plant growth.
The results of observing vines from all over the world surprised her and her colleagues. “I thought we were going to see mostly clockwise plants in the northern hemisphere, and mostly anticlockwise plants in the southern hemisphere,” she said.
“This is what you would expect if the tips of the vines were tracking the apparent movement of the sun across the sky while they were on the sunny side of the tree trunk they are climbing.”
Even though the majority of vines at each site were spiralling to the left, anticlockwise, Ms Moles found some that curled to the right.
“Sometimes all the clockwise ones were of a particular species, but some species have both left-handed and right-handed individuals,” she said.
The study, The global trend in plant twining direction was published in Global Ecology and Biogeography (December 2007)
A Left-Hand Twist In Nature
Ms Moles and her colleagues have theorised that the reason for the vines’ disregard for the Coriolis effect is because of an inherent left-hand twist in the plants' basic molecules
“We tested three different hypotheses for this result,” she said.
“1) that plant twining direction is random; 2) that twining direction is determined by plant tips following the apparent movement of the sun across the sky; and 3) that twining direction is determined by the Coriolis effect.
“We rejected all three. We are now investigating the possibility that the widespread phenomenon of anticlockwise twining arises as a function of the left-handed bias of all biological molecules on earth.”
She pointed out that about 94% of seashells also twist in the same direction.
Why are Seeds the Size they Are?
You might like to read more about Ms Moles' research in Why Are Seeds the Size They Are?
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