Intelligent life: Why don’t we consider plants to be smart?

Plants eavesdrop on each other and communicate with other organisms via subtle messages. So why don’t we recognize them as smart beings, ask two new books

The humble orchid is considered by most people as beautiful but dumb In an early Star Trek episode, the Enterprise is boarded by human-like aliens, with lives lived so fast that the crew can’t see them. For their part, the aliens see Captain Kirk and his crew as near-static beings whose every action seems to take an age to complete.

Human-like Aliens Captain Kirk and his crew

Now think about how we view plants. With their slow-lane responsiveness, they could be ticking the boxes for behavioral brightness but they seem too slow, and too different, to register as intelligent.

This is the core of Brilliant Green by Stefano Mancuso and Alessandra Viola and Plant Sensing and Communication by Richard Karban. Plants are smart, they say but to notice we have to overcome our ingrained cultural biases. As Karban writes: “Ask a child about the differences between plants and animals.

They’ll say, ‘Plants can’t move’ or ‘Plants don’t do anything’.”

And, as both books point out, it is but a short intellectual step to allying apparent immobility with a form of mechanistic half-life of simple growth and response – a flat lined existence devoid of subtlety, strategy and learning.

Islam doesn’t consider plants alive at all, Mancuso and Viola remind us.

Where are the plants?

It has a rich tradition of plant and flower illustration, alongside a ban on the physical depiction of living things.

Description of Nature

And until recently, Western medicine used “vegetative state” to describe people considered to have lost the ability to think or be aware.

In a vegetative state the person is still unconscious. They have no awareness of themselves or their environment.

Clearly, we will never play chess with a rose, nor ask the orchid on our windowsill for advice. But that is the point: humans are guilty of serious parochialism, of defining intelligence in terms of a nervous system and muscle-based speed that enables things to be done fast, say all three authors.

Plants and animals face similar challenges: to find resources and mates, and avoid predators, pathogens and abiotic stresses. In response, says Karban, “plants communicate, signaling within [themselves], eavesdropping on neighboring individuals, and exchanging information with other organisms”. They have adaptive responses that, if they happened at speeds humans understand, would reveal them to be “brilliant at solving problems related to their existence”.

The field was nearly undone by the pseudoscience of the 1970s, when notions such as “vibrations” and “energy fields” were linked with results from poorly designed experiments testing plant sensitivity to music and the human voice, and the ability for each to influence the other’s growth. Though the mechanisms behind these phenomena are now better known (and odder things, like noise-making roots, revealed), many remain skeptical about plant intelligence.

Both Karban and Mancuso have spent their careers trying to find scientifically rigorous evidence of intelligence. Karban studies plants’ immune-like responses to attack at the University of California, Davis, while Mancuso works at the International Laboratory of Plant Neurobiology at the University of Florence, Italy.

They are in good company. From Plato onwards, many thinkers considered plants smart. After working on climbing and carnivorous plants, orchids and germinating seeds, Darwin wrote: “It has always pleased me to exalt plants in the scale of organized beings.” Linnaeus actually believed that plants sleep at night.

Now microelectronics and the analysis of volatile compounds at picogram concentrations are revealing the complexities of plant behavior as never before. So much so that Mancuso can write: “Plant lives unfold in another dimension of time” and that they are “considerably less passive than they appear, and are in fact wily protagonists in the drama of their own lives”.

“Plants’ lives unfold in another dimension… they are wily protagonists in the drama of their own lives”

Plants, say the authors, are highly responsive, attuned to gravity, grains of sand, sunlight, starlight, the footfalls of tiny insects and to slow rhythms outside our range. They are subtle, aware, strategic beings whose lives involve an environmental sensitivity very distant from the simple flower and seed factories of popular imagination.

Anthers of thale cress, as seen through a fluorescence micrograph.

Brilliant Green and Plant Sensing and Communication are timely, highly accessible summaries of fast-developing fields. The former is a popular account (co-written with a science journalist), the latter a more technical take. Both combine a passion for plants and a desire to illustrate their largely unsung complexities with an appreciation of the burden of proof needed to persuade us of a world that contains chlorophyllic sentience. As Spock never said, it’s intelligence but not as we know it.

Avatar. (2009) " ... É uma transdução de sinal. Desta raiz para a raiz da árvore mais próxima". "Olha, com certeza deve ser elétrica, com base na velocidade da reação".

Uma mulher (LUCY) é envolvida com tráfico de drogas, dopada e colocam nela uma droga nova para levar para a Europa. Presa ela é agredida, o saquinho explode e seu corpo absorve as substâncias e ela passa a ter superpoderes, como telepatia, telecinesia, a ausência de dor e a capacidade de adquirir conhecimento instantaneamente aumentando assim a capacidade do seu cérebro. Em paralelo Morgan Freeman dá palestras sobre o percentual do cérebro que usamos, 10%. Os golfinhos usam 20%. E ele diz que não sabemos o que acontece se usarmos mais capacidade. Essa mulher procura esse homem, porque ela sabe que vai morrer logo. Veja o que acontece quando LUCY olha para uma árvore com apenas 20% da sua capacidade cerebral!