Learning by Association in Plants

Abstract

In complex and ever-changing environments, resources such as food are often scarce and unevenly distributed in space and time. Therefore, utilizing external cues to locate and remember high-quality sources allows more efficient foraging, thus increasing chances for survival. Associations between environmental cues and food are readily formed because of the tangible benefits they confer. While examples of the key role they play in shaping foraging behaviours are widespread in the animal world, the possibility that plants are also able to acquire learned associations to guide their foraging behaviour has never been demonstrated. Here we show that this type of learning occurs in the garden pea, Pisum sativum. By using a Y-maze task, we show that the position of a neutral cue, predicting the location of a light source, affected the direction of plant growth. This learned behaviour prevailed over innate phototropism. Notably, learning was successful only when it occurred during the subjective day, suggesting that behavioural performance is regulated by metabolic demands. Our results show that associative learning is an essential component of plant behaviour. We conclude that associative learning represents a universal adaptive mechanism shared by both animals and plants.

Are plants sentient?

“…Some of these are resuscitated by signals such as blue light, known to involve ion flux (Trewavas, 2009). Associative, memory-based, forms of plant learning have recently been reported (Gagliano, 2017;Gagliano, Vyazovskiy, Borbely, Grimonprez, & Depczynski, 2016).…”

The mind of plants: Thinking the unthinkable

“…Plants have been omitted from the conversation because no experimental evidence for their ability to learn by association was available, until now 9 . It is logical then, that the adaptive value of associative learning in vegetal species has never been considered.…”

Pavlov’s pea plants? Not so fast. An attempted replication of Gaglianoet al. (December 2016)

“…Over the last decade, there has been substantial debate in neurobiology and philosophy of mind regarding what kinds of organisms possess the capacity to learn (Gagliano et al , 2016(Gagliano et al , , 2018Thellier, 2017;Gagliano, 2017) , along with thornier issues like cognition (Garzón, 2007;Gross, 2016;Adams, 2018;Segundo-Ortin and Calvo, 2019) and intelligence (Marder, 2013;Trewavas, 2017) . Some of these disputes center around particular terminology and language, but some basic empirical questions remain contentious, including the simple question: can plants learn?…”

“…These studies generally failed to observe conditioning in plants, and those that concluded in favor of conditioning lacked sufficient controls to rule out other explanations, as reviewed by Adelman (Adelman, 2018) . Gagliano et al . (Gagliano et al , 2016) provide the most convincing report of conditioning in plants to date, but there are no published reports of replication, from the original lab or others.…”

“…Associative learning is the phenomenon whereby an individual organism associates two stimuli, and thereafter uses one as an indicator for the other. In Ivan Pavlov's classic work, dogs were trained to associate the ringing of a bell with the imminent arrival of food, and demonstrated the appropriate physiological response of salivation (Pavlov, 1927 (Gagliano et al , 2016) .…”