Plants seem to demonstrate learned behaviour. Dr. Monica Gagliano studied Mimosa pudica, which closes its compound leaves when it is touched or shaken presumably because these stimuli represent threats.
Dripping water onto the leaves may initially be perceived as a threat but is not actually dangerous. At first, when scientists dripped water onto the plants, the leaves closed and slowly opened. After repeating this several times (i.e., “training” the plants), the plants opened their leaves much more quickly after the first drop and opened them fully. Eventually, the water droplets stopped triggering a response—yet the issue wasn’t plant fatigue. Shaking the plant still triggered a strong defensive response (closing the leaves).
In another study, Dr. Gagliano used a Y-maze—think of the classic study design where a lab rat goes down a path (the stem of the Y) and then has to choose between the path on the right or the left. In this case, her research “demonstrated that seedlings of the garden pea are able to acquire learned associations to guide their foraging behavior and ensure survival.”
During training sessions, plants were taken out of the darkness. When a light was projected at one end of the Y, the next morning, the plants faced that way. But some of the plants were trained to associate a fan with a light. Eventually, these plants “learned” to face the fan in the darkness even if it wasn’t in the place where the light was in the previous session, demonstrating, states Gagliano, “the ability of seedlings to anticipate both the imminent arrival of light (“when”) and its direction (“where”) based on the presence and position of a neutral conditioning stimulus [the fan].”
Sources: M. Gagliano, CI Abramson & M Depczynski. Plants learn and remember: let’s get used to it. Oecologia. 2018. Volume 186. Pages 29-31.
M. Gagliano, VV Vyazovskiy, AA Borbély et al. Learning by association in plants. 2016. Scientific Reports. Volume 6. Number 38427.
- Janet Wallace