Stems of wall cress are less elongated in windy conditions due to a touch-response system called thigmomorpho-genesis, that turns on specific genes in response to touch that regulate growth.

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"A small weed that can turn on a specific set of genes when touched has given scientists clues to understanding how plants adapt to their environments. In particular, it may help to explain why plants that are exposed to wind tend to be shorter and sturdier than their more sheltered cousins…One of the genes turned out to be the gene responsible for making a small protein called calmodulin in wall cress. The protein is found in all fungi, plants and animals--although not in bacteria. It is known to have a very important role in processes within cells that are controlled by the concentration of calcium ions - for instance, muscle contraction and the release of neurotransmitters, or chemical messengers, at the synapses between nerves. Each calmodulin molecule binds to four calcium ions. Once it has bound them, it binds in turn to important enzymes, triggering several biochemical important events…this may be a breakthrough in understanding an earlier observation that plants exposed to wind tend to be less elongated than protected plants, and that this effect can be reproduced in the laboratory by touching. Scientists call the touching response: thigmomorpho-genesis." (Boyd 2007)

Web page
Science: Plant switches on genes in response to touchNew ScientistBoyd, Alan

Journal article
Rain-, wind-, and touch-induced expression of calmodulin and calmodulin-related genes in ArabidopsisBraam J; Davis RW

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