Biologists at the College of William & Mary (USA) carried out a peculiar experiment involving the Mimosa pudica plant. This allowed them to conclude that flora possess the ability to distinguish the number of light days they have experienced. The study’s findings were published in the journal Cognitive Science.
The sensitive nature of the Mimosa is what earns it the name “sensitive plant”—when touched, its leaflets rapidly fold inward. However, on this occasion, the scientists focused on another characteristic of the plant: its regular, rhythmic movements known as nyctinasty, which cause the leaves to open during the day and close at night.
The researchers placed the plants within a specialized chamber equipped with controllable lighting. Over 74 days, a specific pattern was repeated: light was provided for 12 hours on two consecutive days, followed by a day of complete darkness. Using time-lapse photography, even minute plant movements were successfully captured.
After a period, the plants’ behavior shifted: during the pre-dawn hours, they exhibited more movement specifically on days when the light was scheduled to turn on, yet were calmer if a dark day was next. This tendency was absent during the first two weeks of the trial, only developing around the fifteenth day.
To determine if the plants were truly tracking the count of light days rather than merely reacting to the time, the task was made more complex. In the second phase of the experiment, the researchers shortened the “day” cycle from 24 hours to 20 hours, and later began altering the day length randomly—ranging from 10 to 32 hours. The plants adapted to these variations without losing their capacity to anticipate the onset of the dark period following two illuminated periods.
Nevertheless, this capability had limitations: if a day lasted less than 12 hours or more than 24, the plants’ internal clock became disrupted, and they could no longer respond correctly. Apparently, a specific duration is required for them to process incoming data.
The authors interpret the experimental outcomes cautiously and acknowledge the necessity of further investigations. However, the data gathered already supports existing evidence suggesting that plants can process intricate information, which proves beneficial for environmental adaptation.
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