Plants, like almost all living organisms, have an internal communication system to respond to external stimuli. Whether they are exposed to sunlight, pollutants, nutrients or pests, plants react with a tell-tale electrical signal.
Now, the EU-funded project PLEASED (PLants Employed As SEnsing Devices) is attempting to understand these signals. And if it succeeds, plants could take on a new role as biosensors.
According to project co-ordinator, Professor Andrea Vitaletti of the University of Rome, plants used as biosensors can be multifunctional. "If you have an artificial device, measuring some parameter like temperature or humidity, it will probably be more accurate than the plant," he says. "But the plant needs to measure a large number of parameters simultaneously in order to survive. So if we could read the signals of the plant we would be able to measure many parameters at the same time."
What the project is attempting to achieve is to classify the different signals plants produce in order to determine what kind of stimulus has been applied. For example, if you know which electrical pattern is typically produced by a sunflower when it is suffering from drought, then you could keep looking for that pattern in sunflowers. The plant will, in effect, be 'telling' you when it wants some water through specific electrical signals.
The challenge, however, is to differentiate between different electrical signals, which might occur simultaneously. At the moment, the project team intends to conduct multiple experiments to recognise the different stimuli. "It is going to take lot of work before we can use the plants practically as biosensors," says Professor Vitaletti.
The proposal is to integrate electronic devices within plants such that they become a kind of cyborg, or plant-borg, as Professor Vitaletti describes them. Ideally, these will be very small devices, the size of paperclips or even smaller, that will be inserted into the plant. These will monitor the signals generated by the plant in its natural environment, analyse them, and combine them with the signals of other plants nearby to produce an analysis of the plants' environment in real time.
So, why we should use plants as botanical sensors? For one, they could be used for monitoring environmental pollution. A practical application currently exercising the minds of the project team is to use plants as certification devices for organic farming.
By observing the signals generated by the plants, it should be possible to determine whether or not the farmer has used adequate chemicals. "If you want to find out the same thing with artificial devices, you would need quite a number of them," says Professor Vitaletti.
The project is due for completion in May 2014. By then the project team hopes to have created the beginning of an open source data set of species of plants, specific stimuli and the corresponding electrical signals.
"What I hope is that the scientific community will continue to increase the size and the quality of this data set," says Professor Vitaletti. "Ultimately, it should be something like the Avatar movie: plants and people in close communication about the world they live in. Fantasy, science fiction, yes, but that’s the popular version of our idea."
Les Hunt
Editor