Did you ever wonder about "Touch me not plant" (লজ্জাবতী): A plant that can learn, remember and evaluate

Photo: Touch me not plant (Lazzabati)

Lock Words

As you are habituated by seeing that touching the plant Mimosa pudica (Touch me not plant/Lazabbati) curls up immediately, It will be difficult for you to believe that it no longer folds it leaves when you touch! Yes, you will see such kind of touch not me plant if you visit Kew Gardens, Southeast London. Lets rediscover our views about lazzabti!

Words to Unlock

The specimens of Mimosa residing in Kew Gardens no longer curl up to the nudging fingers of countless human visitors. So many visitors of the Gardens have been touching these plants to see them perform their trick, that the plants cease to respond. Could it be that the Mimosa plants have learned that being touched repeatedly is a disturbance, yes, but one with no life-threatening consequences and therefore requiring no reaction?

The question underscores a phenomenon known as ‘habituation’, which is considered the simplest form of learning, one that scientists have observed pretty much wherever they have looked. And there is no reason to exclude plants from the effects of habituation merely on the basis of entrenched prejudices. Experimental evidence, combined with a sound theoretical framework that accounts for their behaviour, is required for us to make that call.

Like yawning, shivering, eye-blinking and knee-jerking in humans, the leaf-closing behaviour of Mimosa is an excellent example of an automatic response or reflex. Like all reflexes, Mimosa’s leaf folding trick is an evolutionary survival mechanism developed by members of the species through innumerable generations in the process of natural selection. It is part of the acquired habitus of the species, which has become deeply ingrained over its evolutionary history because it helped the specimens survive. How so?

Mimosa’s leaf folding allows the plant to respond quickly to perceived trouble, in order to protect her from harm. However, it does not come for free. When the plant folds her leaves shut, her capacity to forage for light suddenly plunges by half, meaning that the plant could face the risk of starvation. This risk may be a justifiable price to pay if the danger is real. But it is clearly a waste of precious opportunities to forage for light and thrive, when a perceived dangerous situation turns out to be not dangerous at all.

Mimosa is faced with a persistent emergency situation, urging her to keep evaluating the trade-off between the energetic gain of foraging and the risk of being eaten, constantly choosing between life and death. Wouldn’t it then be surprising to find that Mimosa has little or no control over her own fate? That the plant is incapable of assessing what the circumstances demand and what they offer? That she would be unable to learn from experience, unable to learn to ignore the harmless nuisance of, for example, being touched by yet another human finger visiting Kew Gardens, so as to spare herself the unnecessary trouble (and energy loss) of closing her leaves?

It would be surprising, indeed! Actually, this is not what these plants do: they learn. What we observe inside the controlled settings of a scientific laboratory as well as outdoors in places like Kew Gardens confirms that plants can learn, remember, evaluate the choices they are faced with, and make decisions. So, the true surprise is our insistence on thinking that plants can respond only in pre-programmed and automatic ways already encoded to their DNA or that, devoid of agency, they are somehow being acted upon rather than acting in their own right.

Acknowledgment: Botany One

What wonder next! Well, wait till the next article get published.