Peas and pea plants don’t have brains. Yet, scientists say, they can make
risky decisions – they can judge risks efficiently. Hagai Shemesh, a plant
ecologist at Tel-Hai College in Israel, and Alex Kacelnik, a behavioural
ecologist at Oxford University in England, conducted experiments with pea
plants – the results were published in the June 2016 edition of Current
Biology.
The researchers grew pea plants in adjoining pots, or punnets. Each dual
pot had a plastic dividing barrier between them. The researchers split the
roots of the plants so that half of the roots were in one pot and the other
half of the roots were in another pot.
Both pots had the same amount of nutrients on average, but in one pot the
nutrients levels were constant, and in the adjacent pot, the nutrient levels
varied over time (they were unpredictable). Nutrients are substances in the
soil that plants require for growth. Then the researchers switched the
conditions so that the average amount of nutrients in both pots would be
equally high or equally low. They wanted to find the answer to the question:
Which pot would the pea plant prefer?
The results showed that when pea plants had a choice between constant
levels of nutrients and varied, unpredictable levels of nutrients, each plant
chose the unpredictable pot – but only when the conditions were poor (i.e. when
their wasn’t enough nutrients to be healthy plants).
When nutrient levels were low, the plants laid more roots in the
‘unpredictable’ pot. But when nutrients were high and abundant, the plants laid
more roots in the ‘constant’ pot (the pot where the levels of nutrients never
changed). The ecologists maintain that the plants ‘somehow knew the best time
to take risks.’ ‘They are less than pea brains, they are no brains,’ said Dr.
Kacelnik, ‘but they did it.’ Evolutionarily, this makes sense for a plant
trying to survive.
This complex behaviour in a plant supports an idea known as risk
sensitivity theory – when choosing between stable and uncertain outcomes, an
organism will choose stability when things are going well, and choose to take
risks when times are difficult. How brainless pea plants evaluate risk is still
unclear, but the researchers think they must be following rules, not reasoning.
The researchers raise the question about the experiments association with
humans. But the risk sensitivity theory doesn’t explain why people make risky
decisions under all conditions, especially when deciding over short-term versus
long-term situations. But people have something that plants don’t have –
brains!
Plants don’t worry about feelings. Nor do they over-think the situation.
The simplicity of pea plants makes it easier to create tests and experiments
because plants don’t worry about feelings, or the expectations of other plants
– but they do seem to know about the consequences of their actions.
MARTINA NICOLLS is an international
aid and development consultant, and the author of:- The Shortness of
Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet
(2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).
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