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Growing crops without soil may sound like a contradiction, but for the research team "Eplants" (Electronic Plants) at Linköping University, Sweden, led by Associate Professor Eleni Stavrinidou, it is not only possible, but also groundbreaking.
The team has developed an innovative "bio-electronic soil" (E-Soil) that boosts the growth of barley crops by 50% when their roots receive electrical stimulation through it. This prototype is an electronically conductive substrate designed specifically for hydroponic crops.
Stavrinidou explains that "the global population is growing and climate change clearly shows that we cannot meet the planet's nutritional needs with existing agricultural methods alone. With hydroponics, we can grow food in urban environments under very controlled conditions."
We spoke with the Cypriot physicist, who studied at Aristotle University of Thessaloniki and Ecole Nationale Supérieure des Mines de Saint Étienne in France and specialized in nanotechnology and bioelectronics. She currently teaches and conducts research at Linköping University on the application of bioelectronics to plants.
According to the study published in Proceedings of the National Academy of Sciences, E-Soil is made of organic materials mixed with a conductive polymer called PEDOT, which is used in common objects such as sensors and OLED displays.
The researchers examined the effect of electricity on barley plants for 15 days before harvesting and found that applying a low voltage from E-Soil electrically stimulated their roots, leading to a 50% increase in biomass compared to non-stimulated plants.
The researchers also observed that nitrogen, one of the main nutrients involved in plant growth, was processed more efficiently by the plant through stimulation. "However, despite this finding, we still do not fully understand how stimulation affects nutrient processing," she added. She said that this is what future studies will focus on.
Stavrinidou also said that "bio-electronic soil" is environmentally friendly, as it is derived from cellulose and the conductive polymer, and works at low voltage, making it a safe alternative to previous methods that required high voltage and non-biodegradable materials.
E-Soil consumes low energy and reduces resource consumption. The study also suggests that this technique could reduce the use of fertilizers in agriculture.
Falling into the fly trap
Bioelectronic technology enables advanced research on how plants respond to their environment and stress. Ms. Stavrinidou's work has led to discoveries about the electrical signaling that triggers the closure of the trap of the carnivorous plant.
Plants, like humans, produce electrical signals in response to touch and stress, even though they lack a nervous system. Unlike animals that can move, plants have to cope with stressors such as wounds from herbivores or attacks on their roots.
"Today, there is a great need to grow more resilient plants to environmental challenges, to be able to grow food and keep forests healthy in the future.
That's why it's important to understand how plants respond to stress, and I think this new technology can help with that," she says. She explains that in some plants, electrical signals are linked to rapid movements.
The researchers use the carnivorous plant Venus Flytrap as a model for rapid electrical signaling in plants. The natural trap of this plant has small sensory hairs on the inner side that can close with a simple touch.
The insects that get trapped are digested by an enzyme and their nutrients are absorbed by the plant. But to close the trap, the hairs need to be touched twice within about 30 seconds. By not closing quickly every time a hair is stimulated by other causes, the plant saves energy.
Electrical signaling in living organisms is based on the voltage difference between the internal and external environments of cells due to the movement of electrically charged atoms. When a signal is triggered by a sensory hair, for example, ions flow very quickly through the cell membrane, and this rapid change in voltage causes an impulse to spread.
In their study, published in Science Advances, the researchers demonstrate a multi-electrode array technology used to study the generation and propagation of the electrical signal in a Venus Flytrap.
The newly developed measuring device consists of a very thin electrode film, as thin as food plastic wrap, that follows the shape of the outside of the plant's pods. The researchers stimulated a sensory hair and used about 30 electrodes to measure the signal in the plant's lobe and filmed its movements to correlate them with the closure of the trap.
"We can now say with certainty that the electrical signal comes from the sensory hairs of the plant, but also that it spreads mainly radially, without any clear direction," concludes Dr Eleni Stavrinidou.
There is also Cyprus!
Eleni Stavrinidou's brother stated in his personal account, "The creation of artificial soil for crops without soil may sound like a contradiction, but for the research team 'Eplants' (Electronic Plants) at Linköping University, Sweden, led by Associate Professor Eleni Stavrinidou, it is not only a reality, but also a world news!"
