Another entry written by Tamara Bonnemaison, who scribes:
Mimosa pudica, or sensitive plant, folds up its leaflets in response to touch or movement. This species was featured by Taisha in-depth earlier this year (February) as part of a series about the nastic movements of plants. Taisha’s entry on Mimosa pudica provides great background information on the sensitive plant while also describing the mechanics of nastic movements.
The reason I am revisiting this species so soon after Taisha’s entry is because of a publication made after that posting. In May, Dr. Monica Gagliano et al. published the results of a study demonstrating that Mimosa pudica is able to learn and “remember”. In Experience Teaches Plants to Learn Faster and Forget Slower in Environments Where it Matters, (Oecologia, 175(1):63-72), Dr. Gagliano (an animal ecologist) and her research team used methods typical to the study of animal behaviour to understand how Mimosa pudica acquired learned behaviour.
Key to this study was the sensitive plant’s ability to fold its leaves when touched, dropped, or shaken. The researchers used a controlled drop system to prompt the touch response. After being dropped multiple times, it was observed that the Mimosa leaves would stop folding when disturbed in this way. In other words, the plants became habituated to being dropped. Intriguingly, plants that were in low-light conditions more quickly learned to remain open upon being dropped compared to plants that were not stressed for light. This learned behaviour was retained over a period of four weeks, even if the low-light plants were subsequently exposed to higher light levels.
The research of Dr. Gagliano and her team is part of a developing field of science dubbed “plant neurobiology” (though plants do not have a nervous system), where the process of science is being applied to how plants learn from and respond to their environment. Michael Pollan covered the topic of plant intelligence in a December 2013 article in the New Yorker: The Intelligent Plant: Scientists debate a new way of understanding flora.