Cucumber coils revealed, according to reports in ScienceNOW, ScienceDaily 30 August 2012 and Science vol. 337, p1087 DOI: 10.1126/science.1223304 31 August 2012.

In 1865 Darwin published a book entitled On the Movements and Habits of Climbing Plants in which he describes how cucumber tendrils attach to a support and then form two helical coils, each one wound in the opposite direction to the other with a loop connection between the two (called a “perversion” by Darwin). Darwin noted this structure acted like a spring, but was not able to explain how it worked.

A team of researchers at Harvard University have now studied the tendrils and discovered how the coil is formed and how it functions. The coil is formed when a double layered ribbon of gelatinous cells shrinks on one side, but not on the other, as it dries out. This asymmetrical contraction results in the two opposite helices forming. The coiling ensures the tendrils are not broken by movements from wind or being bumped by a passing animal. However, unlike a man-made coiled cord, when the tendril is stretched it doesn’t just flatten out. Sharon Gerbode, one of the researchers explained: “It’s easy to create one of these twistless springs with a telephone cord and they’re annoying. But with the phone cord, you can pull on both ends and it will straighten out into a flat ribbon. What’s strange about the cucumber tendril is that if you pull on the ends, it actually overwinds, adding more turns to both helices”. This overwinding increases as the tendrils age, so they become stiffer, and form a stronger support as the plant becomes laden with fruit.

Gerbode commented: “Nature has solved all kinds of energetic and mechanical problems, doing it very slowly and really getting it right”. The research team eventually got it right when they developed a mathematical model of the coiling behaviour and built a model from silicone, fabric and wire that had the same combination of properties as the cucumber tendril cells, and this responded to stretching by overwinding, just as the tendrils did.

The researchers suggest that tendril formation is an adaptation that enables the plant to have the advantage of height without having trunks and branches. Another member of the research team, Lakshminarayanan Mahadevan explained: “The advantage of using a tendril is that the plant saves on complex machinery to build structural supports such as trunks and branches. The disadvantage is that it must depend on other species to build these supports. Thus, tendrils are an adaptation that is likely to develop only in regions replete with vegetation that can provide supports and where competition for resources is intense”. Mahadevan went on to ask: “The real question remains this: how difficult is it to evolve such tendril-like solutions?”


Editorial Comment: The researchers are correct in observing that a cucumber uses tendrils to gain height and can only do so in an environment where plants with suitable support structures already exist. It is also true that the coiled tendrils do enable the plant to gain height without having trunks and branches, but this therefore means tendril formation cannot be an adaptation! The logic is simple: if cucumbers had already evolved without tendrils then they had to already be surviving fitly without this coiling device, so therefore they had no need of them. Therefore, they couldn’t have gained them as adaptations in any evolutionary sense. All observed adaptations are actually the ability of living things to change in structure and/or function in order to cope with changes in its environment. However, adaptations only work if the organism already has the necessary genetic information for the altered structure or function. Adaptation is therefore a design feature that must be built into the plant prior to experiencing any environmental challenges.

Since there is no evidence that cucumbers have changed from being a plant that did not have coiled tendrils, plus it’s a fact that the presence of things to climb, such as trees with trunks and branches, never enables cucumbers or any other plant, to make tendrils if they don’t already have the right kind of cells to form them. So the answer to the research team’s question “how difficult is it to evolve such tendril-like solutions?” is that it is impossible to evolve such tendrils by chance evolutionary processes.

In addition we can add our usual comment that’s so obvious you have to not want to see it in order to miss it. The fact that it took intelligent biologists to discover the structure and function of cucumber tendril cells, and a team of physicists, mathematicians and engineers, to mechanically copy the tendrils, should tell them this. From Darwin onwards, all the scientists, who have studied cucumber tendrils have no excuse for ignoring the evidence of creative design and should give the honour to the Creator God, not to some false god named Nature.

Evidence News 26 September 2012

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