The sensitive plant, Mimosa pudica, folds its leaves when touched. In a 2014 study, Monica Gagliano's team dropped potted plants 15 centimetres again and again. They soon stopped folding for the harmless drop, and still ignored it at least 28 days later.
Truth label: Debated. Serious people disagree. You get both sides.
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Not just tired
The plants still folded when shaken, so they had not simply worn out. They seemed to learn that the drop was safe.
Why bother?
Folding has a cost. While the leaves are shut, the plant's photosynthesis drops by about 40 percent.
Why it's debated
Scientists disagree on whether this should be called learning and memory, since plants have no neurons. Neither proposed mechanism for it is generally accepted yet.
Learn
- How it folds. A touch sends an electrical signal to small joints at the base of each leaflet. Water rushes out of cells there, and the leaflets collapse.
Test yourself
How long did the plants keep ignoring the drop?
At least 28 days. They did not react to dropping for at least 28 days after training.
Sources
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