How plants fight back

A  Recent research has shown that plants are more aware of their environment and more active in their responses than was ever previously imagined. Simon Gilroy, a professor of botany at the University of Wisconsin-Madison in the USA, has spent much of his career trying to understand how plants work. Now, Gilroy and one of his postdoctoral researchers, Masatsugu Toyota, have produced a series of videos that shows how plants responded when they subjected them to wounds, including scissor cuts and caterpillar bites.

B  Gilroy and Toyota discovered that when one part of a plant is attacked or damaged, a wave of calcium spreads throughout the rest of the plant. The calcium alerts the plant to danger and the need to deploy defence tactics. The team were able to see this by utilising a naturally occurring fluorescent-green protein which binds to the calcium, making its path visible.

While scientists already knew that plants reacted to danger via an electrical charge that moves across the plant, they didn't know exactly how it happened. Gilroy and Toyota suspected it had something to do with calcium and were able to confirm their suspicions. They were also able to reveal how glutamate — an abundant neurotransmitter in animals — triggers this wave of calcium.

C  The find was fortuitous given that Gilroy hadn't intended to study wounding at all. His real passion is understanding how plants sense gravity and seem to know which way is up — something that's proving extremely hard to work out. It was during the early stages of an experiment into gravity that Toyota came across the wounding response.

'We work very intensely on the calcium signal, because it's a ubiquitous signal. Biology uses it absolutely everywhere,' explains Gilroy. 'It makes your heart beat, it makes your muscles contract. Plants use it for a lot of their signalling machinery. We had some hints that the gravity-sensing system is based around the calcium signal, and so we were developing the technology to image calcium cells in real-time.' It was during this process that Gilroy and Toyota realised they'd captured something never usually visible to humans.

D  The team found that the calcium travels at one millimetre per second, fast enough to spread to other leaves in just a couple of minutes. From the data collected up to now, it appears that how far the calcium travels depends on the extent of the wound, or, as Gilroy puts it, 'The more you hurt it, the louder it screams.'

That 'scream' can result in a range of responses. 'Plants are masters of chemistry,' says Gilroy. We deal with the world by running away from it, plants deal with the world by growing in response to it, or by making a tonne of stuff. That 'tonne of stuff' could be chemicals that poison a hungry insect, or that make the plant unattractive, tough or unpalatable. Some plants even make proteins that block the ability of a caterpillar's gut to digest the plant material. This is dinner that fights back.

E  The next step for Gilroy and his team is to delve deeper into the signalling response on a cellular level, dissecting the genes and proteins responsible. In contrast to our understanding of human nerve cells, Gilroy admits that the equivalent responses in plants are still barely understood. He is also going to widen the scope of the study and look at other signals that plants send out — signals regarding temperature and changes in light and touch.

Gilroy explains that there may be a wider use for the research, albeit a long way in the future. Once scientists have managed to identify the specific genes that make the signalling process work and can understand what happens when you switch those genes on and off, it's not hard to think about the potential. 'You can imagine that we should be able to take a crop plant and switch on its defences on-call,' says Gilroy. 'We're nowhere near that point yet, but once we get there — say you're in a field and you predict there's going to be an outbreak of some pest, you could go in and pre-defend all of the plants in the field, but you do it on-call so the plants aren't wasting their resources defending themselves the whole time.'

F  For now, though, Gilroy is happy to simply increase understanding of plants. He is energetic in his insistence that they are not the inactive and unreceptive organisms that people generally believe them to be. For that reason, he's as enthusiastic about the way the videos bring the response process to life as he is about the future potential of the research. 'When you look at a plant, just because it doesn't do what we do, and it doesn't move, that doesn't mean it isn't doing anything. They're hugely dynamic organisms,' he says.

Conscious and Unconscious Thought

Great scientists and artists have long known about the unconscious mind. The founder of psychoanalysis, Sigmund Freud, argued that most of our real motivation lies below conscious awareness and that we require the services of a psychoanalyst to explain ourselves to ourselves. Even those celebrated scientists who believe that Freud exaggerated the importance of the unconscious argue that it is a part of the in our minds which we should learn to control and take advantage of.

The great mathematician Alfred North Whitehead seemed to be a supporter of unconscious mental processing when he said: 'It is a profoundly erroneous truism, repeated by all copybooks and by eminent people making speeches, that we should cultivate the habit of thinking about what we are doing. The precise opposite is the case.' What Whitehead meant by this is that some of the greatest breakthroughs in creativity occur when a problem is consciously shelved for a while — 'don't think about it, just sleep on it' — after which the unconscious mind offers a solution. This is a process which psychoanalysts call 'incubation'.

Now the latest psychological research confirms that we can all incubate a problem to our own advantage. Ap Dijksterhuis, a psychologist at the University of Amsterdam, has recently published a series of experiments in which students were presented with complex everyday problems to solve. In one experiment they were given the opportunity to think carefully about a decision; in another experiment they were distracted by an irrelevant task whilst making a decision. The surprising result, published in the Journal of Personality and Social Psychology, was that 'unconscious' thinkers made the better decisions.

Timothy Wilson and colleagues from the University of Virginia's psychology department conducted another experiment. Participants were presented with five posters and asked to choose one to take home. A little later, they were telephoned and asked how satisfied they were with their choice — a measure of whether they had made the right decision from a subjective point of view. Some participants had picked their poster straight away, whereas others were asked to analyse carefully the pros and cons of each poster. It turned out that people who had analysed were less satisfied with their choice than people who had not applied logic. Paradoxically, it seems that those who had consciously weighed up the various attributes had made relatively poor decisions.

The conclusion that has to be drawn from current research suggests the somewhat counter-intuitive idea that the more complex a problem is, the less likely it becomes that conscious thought can contribute much. If a dilemma is particularly difficult, a lot of information has to be taken into account and it appears that conscious thought is not good at this. The message is that when it comes to intricate problems with many variables, you should let the unconscious deal with it.

Using dreaming is one way of doing this. Dreams are the part of sleep most strongly correlated with rapid eye movement (REM) and have been associated with enhanced creativity and novel solutions. The latest research suggests that, if you want to enhance unconscious problem-solving, you should try to think about your problems immediately after dreaming. In a recent experiment, psychiatrist Matthew Walker and colleagues from the Laboratory of Neurophysiology at Harvard Medical School woke up half of their experimental subjects immediately after REM sleep, and the other half just after sleep with no dreams, and then asked them to solve crossword puzzles. REM awakenings provided a 32 per cent advantage in the number of puzzles solved, compared with non-REM awakenings.

But you don't have to be asleep to use the unconscious mind. When you are not thinking of anything in particular, which is why daydreams are so useful in the quest for creativity. Daniel Goleman, the famous psychologist who proposed the theory of 'emotional intelligence', urges us to be more aware of, and discount, a key obstacle that the conscious mind imposes on the unconscious: that of self-censorship. This is the voice that whispers to you, 'they'll think I'm foolish' or 'that will never work', keeping you imprisoned within the boundaries of what is deemed acceptable. Howard Gardner, a professor of cognition and education at Harvard University, suggests that we free ourselves from the straitjacket of always doing things the same way. In seeking to go beyond the routine and conventional, you will gain confidence in trusting your unconscious, he says.