These effects aren’t confined to Mimosa pudica– all plants are probably susceptible to anaesthesia, it is just that the effects are more dramatic in fast movers like Mimosa plants and Venus flytraps.
If plants can be “put to sleep”, does this mean they exist in a state of awareness that is shut off by anaesthetics? Might we consider this state to be a kind of sentience, a subjective internal experience? If so, do plants have some form of consciousness? These are controversial ideas, but Calvo and a small group of plant behaviour researchers take them seriously. Their findings so far, though tentative, could disrupt our understanding of consciousness – not to mention our attitudes towards plants.
First, cognitive behaviour is flexible and dynamic, rather than being a repeated, knee-jerk reflex. Second, it is predictive: it indicates that the organism is anticipating changes in the environment. Finally, it is goal-directed: it causes a change in the environment or in the organism.
Sentience is the capacity to experience sensations and feelings. The notion that all life possesses it, to a greater or lesser degree, is gaining ground. “Why stop at plants? Bacteria, fungi and slime moulds all do very clever things despite being more rudimentary,” says evolutionary ecologist Ariel Novoplansky at Ben-Gurion University of the Negev, Israel.
They are finding that plants have a sophisticated awareness of their environment and of each other, and can communicate what they sense. There is also evidence that plants have memory, can integrate massive amounts of information and maybe pay attention. Some botanists argue that they are intelligent beings, with a “neurobiology” all of their own. There’s even tentative talk of plant consciousness.
Parallels with animal intelligence don’t end there. Besides the tantalising brain-like behaviour of the root’s transition zone, many plant cells are capable of neuron-like activity. “In plants, almost every cell is able to produce and propagate electric signals. In roots, every single living cell is able to,” says Mancuso. Likewise, the phloem is extremely electrically active, and capable of fast electrical signalling. “It is some kind of huge axon, running from the shoot tip to the root tip,” says Baluska.
There’s also the curious fact that plants produce chemicals that in animal brains act as hormones and neurotransmitters, such as serotonin, GABA and melatonin. Nobody quite knows the significance of these chemicals in plantsFull articles from New Scientist here and here.