Why do vines curl?
If you walk out in nature, it may not take much time for you to observe vines that curl and wrap around tree trunks and branches. Why? And in what direction?
Vines use the other plants or trees as support for rootlets or tendrils that grow from the vines. I hypothesized that the winding or curling action may provide a more stable foundation in many cases instead of a single linear upward movement.
I researched some theories online and in reference articles. Certain plants and vines spiral clockwise as they grow (right direction) and some spiral counterclockwise (left direction). Is it determined by which hemisphere you are in and influenced by the Coriolis Effect? It could be tested by finding spirals in both northern and southern hemispheres and comparing their directions. However, many vines spiral in both directions. Given that the Earth does not arbitrarily change its rotational direction, this behavior must be explained by some other explanation.
Among the theories are that the spiral will try different directions to maximize its contact and support and/or the spiral is influenced by the night-day cycles.
I found a theory called a “genetic spiral” that suggests the direction of helicity in various helical-patterns in living plants and animals usually solely depends upon genetic make-up.
Next I found a fascinating article that described how samples of fire moss that travelled onboard the space shuttle Columbia did something odd: they spiral. Scientists say it’s a clue to the fundamental inner workings of plant cells. “Moss from space shuttle Columbia (STS-87) shows spiral growth patterns that emerged in low-gravity.” Biologist Fred Sack carefully lifted a petri dish from the tray. Inside were precious samples of moss just back from a two-week voyage aboard space shuttle Columbia. He glanced at the growing clumps, blinked, then looked closer. It was not what I expected to see,” recalls Sack. His moss was growing in a spiral.
On Earth, moss spores that take root send out hundreds of tiny filaments known as protonemata. These filaments normally grow in an unruly fashion and make a messy-looking tangle. But the moss onboard Columbia behaved differently. “As if choreographed, the protonemata swirled together in the same direction. They formed a distinctive clockwise spiral like no moss on Earth.”
Much more needs to be learned about the mechanism of spiraling. Gravity apparently has nothing to do with plant’s chirality (or “handedness”) or spiraling. Darwin proposed that it was “autonomously induced,” which came to be known as the internal oscillator theory. In the 1960’s the gravitropic overshoot theory explained mathematically how circumnutation could spontaneously occur as a result of forces related to gravity and growth. As noted, recent experiments on the space shuttle have demonstrated that gravity is not necessary for circumnutation.
Climbing plants exhibit a predominance of right-handed helical growth, but it cannot be explained by a hypothesis attempting to link plant growth behavior and global location. An alternative hypothesis for the findings is that the widespread phenomenon of anticlockwise twining arises as a function of microtubule orientation operating at a subcellular level. Actin filaments as well as microtubules are all chiral polymers, meaning they form spiral structures with defined orientation.
One article included, “The mechanical or physiological basis for dextral versus sinistral orientation of circumnutation among apically twining plants has not been determined.” I found an article in Science that stated “tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions.” Wow.
Here I have described many scientific hypotheses that may account for plant curling. But to leave out a major consideration—plant intelligence—would be wrong. I have seen countless examples of plants connecting to other plants in seemingly random patterns, their twining wrapping around each other, some even from a distance away. As noted in one article, “We now have dozens of research papers, hundreds of articles, and hours of video prepared and published by plant biologists and neurobiologists discussing the many facets of plant intelligence. Through rigorous research and experimentation, the following behavioral characteristics have now been established and can be attributed to plants: communication, learning, problem solving, and memory & memory recall.”
Plants have the ability to communicate with one another and the ability to share information and resources between organisms. The communication occurs through underground Mycorrhizal networks, or cobweb-like networks of mycelial growth that grows around the root structures of trees and plants. These Mycorrhizal networks have affectionately been dubbed the “Wood Wide Web,” that can be used for anything from nutrient transportation to signaling a potential threat. By creating an internet-like communication network, it may even allow an entire forest to communicate. Given that plants are stationary and cannot flee from predators, communication has been a very important adaptation to combat their mobility limitations. Curling and twining may be a form of communication yet to be discovered.
How can you observe these mysteries of nature?
Get out and enjoy The Great Florida Outdoors!
Dr. Norman is an advanced master naturalist graduate of the FMNP program from UF and a board-certified dermatologist based in Tampa and Riverview. He can be reached at 813-880-7546.
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