Known by many names, such as Humble Plant, Shy Plant, and even Shameplant (Royal Horticultural Society, 2020), the Mimosa pudica is truly unique. As shown in Figure 1, below, M. pudica displays a bright pink flower and many smaller leaves. At first glance, it may seem like any other plant you might come across in the wild, though many amateur botanists and plant-lovers alike have grown it in their homes due to its bizarre behaviours. This plant learns through interesting mechanisms typically only associated with humans and animals.
M. pudica has extremely sensitive leaves. Upon any form of touch, the leaves shrink and shrivel. This behaviour is shown in Figure 2, below (Hagihara and Toyota, 2020). In 1965, Holmes and Gruenberg studied the effects of two stimuli on M. pudica. Specifically, they used a drop of water and a finger. Much to their surprise, M. pudica could discriminate between the two. This came as a shock as, during this time, many believed that plants exhibited the same tissues as humans do, including central nervous systems. It seemed simple, though; plants have central nervous systems and are therefore capable of learning such behaviours. But, plants do not have central nervous systems (Abramson and Chicas-Mosier, 2016), so how does this learning occur?
In general, there are two paradigms for learning; associative and non-associative. Associative learning is characterized by the connection between stimuli and behaviour (Houwer, 2009). Classical and operant conditioning are examples of this. In 1971, Razran studied classical conditioning in M. pudica by slight and strong tactile stimulation. M. pudica closed to a lesser extent with slight touch versus strong touch. The reward in this instance was protective and defensive mechanisms as a result of light touch (Razran, 1971).
Non-associative learning has been studied to a greater extent. More specifically, habituation has been studied in M. pudica. Habituation has been defined as the desensitization to a stimulus over time (Thompson and Spencer 1966; Rankin et al., 2009). Habituation could not be fully substantiated in Applewhite’s 1972 study, inspired by Holmes and Gruenberg’s 1965 study; M. pudica‘s leaves never fully closed regardless of stimuli repetition. As of present, there is not much literature regarding plant mechanisms, though it is becoming an increasingly pertinent topic.
M. pudica‘s learning abilities are still largely unclear and in the past few years, interest in this topic has increased exponentially, especially in the areas covered here, such as habituation and conditioning. These behaviours are ubiquitous throughout the plant and animal kingdom and continue to be studied with great interest.
Works cited
Abramson, C.I. and Chicas-Mosier, A.M., 2016. Learning in Plants: Lessons from Mimosa pudica. Frontiers in Psychology, [online] 7. Available at: 10.3389/fpsyg.2016.00417 [Accessed 6 Nov. 2020].
Applewhite, P.B., 1972. Behavioural plasticity in the sensitive plant, Mimosa. Behavioural Biology, [online] 7(1), pp.47–53. Available at: https://doi.org/10.1016/S0091-6773(72)80187-1 [Accessed 6 Nov. 2020].
De Houwer, J., 2009. The propositional approach to associative learning as an alternative for association formation models. Learning & Behavior, [online] 37(1), pp.1–20. [Accessed 6 Nov. 2020].
Hagihara, T., Toyota, M., 2020. Mechanical signalling in the sensitive plant Mimosa pudica L. Plants, [online]. [Accessed 6 Nov. 2020].
Holmes E., Gruenberg G. (1965). Learning in plants. Worm Runner’s Dig. 7 9–12. [Accessed 6 Nov. 2020].
Project Noah, 2012. Sleeping Grass/Touch-me-not. [online] Project Noah. Available at: <https://www.projectnoah.org/spottings/15810467> [Accessed 7 Nov. 2020].
Rankin, C.H., Abrams, T., Barry, R.J., Bhatnagar, S., Clayton, D.F., Colombo, J., Coppola, G., Geyer, M.A., Glanzman, D.L., Marsland, S., McSweeney, F.K., Wilson, D.A., Wu, C.-F. and Thompson, R.F., 2009. Habituation revisited: An updated and revised description of the behavioural characteristics of habituation. Neurobiology of Learning and Memory, [online] 92(2), pp.135–138. Available at: 10.1016/j.nlm.2008.09.012 [Accessed 6 Nov. 2020].
Razran G. (1971). Mind in Evolution: An East-West Synthesis of Learned Behavior and Cognition. Boston, MA: Houghton Mifflin. [Accessed 6 Nov. 2020].
Royal Horticultural Society 2020. Mimosa pudica | sensitive plant/RHS Gardening. [online] Rhs.org.uk. Available at: <https://www.rhs.org.uk/Plants/21000/i-Mimosa-pudica-i/Details> [Accessed 6 Nov. 2020].
Thompson, R.F. and Spencer, W.A., 1966. Habituation: A model phenomenon for the study of neuronal substrates of behaviour. Psychological Review, [online] 73(1), pp.16–43. Available at: 10.1037/h0022681 [Accessed 6 Nov. 2020].
Comments
5 Responses to “UnbeLEAFable: the learning behaviours of the Mimosa pudica plant”
Hello!
I chose to write this post about the Mimosa pudica plant as I wanted to explore the interesting and unusual behaviours exhibited by plants. Largely inspired by PAIx, I wanted to understand more about plants and why they are not as passive as previously believed. We also discussed plant resistance versus tolerance, and I thought M. pudica’s leaf-closing mechanism was a terrific example of plant tolerance. Furthermore, Neuroscience can be connected to this topic as non-associative learning has been greatly impacted by the discovery of the voltage-dependent channels, those of which we have investigated during the course of this project.
I hope this blog post offered you an insight into the meaningful actions of plants, and more importantly, I hope you learned something new.
All the best,
Aoife H
Hi Aoife,
Great blog post! I found your topic really interesting, and it’s clear that you put a lot of research into it. I feel like every time I read up on some recent studies on plants, my mind is totally blown, and this was no exception! It’s fascinating that such a Humble Plant (literally!) can tell us so much about what it means to ‘learn’. One question that you brought up in the post, how plants can learn without a nervous system, was really interesting to me — if you have the word count, I think that would be interesting to develop a little further. I also found myself wondering how in the 1965 Holmes and Gruenberg study they determined that the plant could tell the difference between water drops and a finger!
I have a couple of specific suggestions that I hope will help you as you edit the post:
– I don’t think you need to specify “M. pudica” in brackets the first time you mention it, as it’s convention to refer to species with that short form after you write out the full name once!
– I would place your figure citations in the figure captions, rather than where you mention the figures in text
– At the end of paragraph 1, I think your point would come across a little more clearly if rather than “At first glance, it is another plant you may come across if you were in the wild, though…”, you phrased it as “At first glance, it may seem like any other plant you might come across in the wild, but…” or something similar!
– In your third paragraph, I think your introduction of the two paradigms for learning as its own ‘section’ is a little unnecessary — I think it would work just as well as a simple sentence like “In general, there are two paradigms for learning: associative and non-associative”, which would also disrupt the flow of the post a little less
– I think you forgot an italicization of “M. pudica” in your conclusion
– The conclusion might also benefit from a quick summary of what was discussed in the post!
Overall, awesome job with this post! I hope these suggestions were helpful!
Happy editing,
Helen
Hi Helen,
Thank you for reading my post and giving me great suggestions. I have put them to use and they have certainly improved the quality of it!
Best,
Aoife H
Hello Aoife,
Your blog post was excellent. It was well-written, informative, and I appreciate the in-depth background research. I have a few suggestions that might help you in your editing process:
1. In your first paragraph, it looks a bit messy due to the number of in text citations mid sentence. I would recommend cleaning this up by combining citations in brackets at the end of one sentence, instead of having multiple mid sentences.
2. Also, in your first paragraph you wrote “At first glance, it is another plant”, this sounds fragmented. I would suggest changing this to “At first glance, this may look like just another wild plant” or something along those lines.
3. In your first paragraph, the last sentence does not flow with the points you bring up. I would suggest making it a full sentence or connecting it to the previous sentence, such as the behaviour of the plant.
This was a very nice piece, keep up the great work. Best of luck in the editing process.
Best,
Jas
Hi Jas,
Thank you for your great suggestions. I’ve taken them into account and applied them to my post. Thank you for your help!
Best,
Aoife H