Sunflower 'optical illusion' could inspire smarter farming and new technologies
Baku, November 4, AZERTAC
Sunflower seedlings can experience something resembling an optical illusion, turning toward a weaker light source even when two much stronger lights are shining on them, Israeli researchers have discovered, revealing how plants process information about their surroundings without a brain or nervous system, TPS-IL reported.
The findings offer new insight into how living organisms process complex information without a centralized control system. They could eventually help improve agricultural lighting and shed light on how cells and bacteria sense their environments and coordinate responses.
Researchers at Tel Aviv University found that plants combine signals from light receptors distributed along their stems. When light arrives from several directions, interactions between these signals can produce surprising growth responses.
In one experiment, researchers positioned two equally strong lights opposite each other and placed a third, weaker source at a right angle. Rather than growing toward either of the stronger lights, sunflower seedlings bent toward the weaker one, as the signals generated by the opposing sources counterbalanced each other.
Unlike animals, which typically rely on specialized sensory organs and a central nervous system, plants gather information through receptors distributed across their bodies. Light-sensitive receptors in the outer layer of the stem detect illumination locally and convert it into biological signals that collectively influence the direction of growth.
When Light Signals Collide
The researchers exposed sunflower seedlings to blue light from different directions and at varying intensities, documenting their movements for more than 20 hours. The plants generally bent toward the stronger of two opposing light sources, but their responses were not proportional to the difference in brightness.
A light source twice as intense as another did not produce a biological signal twice as strong. This nonlinear response means plants do not simply add up incoming light. Instead, they combine signals that have already been processed by their receptors, producing a response that can differ from what the physical distribution of light alone would suggest.
In a study published in the peer-reviewed journal Proceedings of the National Academy of Sciences, the researchers describe this process as responding to the “vectorial sum of transduced signals” rather than the physical sum of the incoming light stimuli.
The findings could eventually help improve artificial lighting systems in greenhouses and indoor farms. Understanding how plants respond to light arriving from different directions could help growers arrange illumination to encourage desired growth patterns while using energy more efficiently.
The research could also have applications beyond agriculture. It may inspire decentralized sensing technologies that process information through multiple small sensors rather than a central controller. In addition, it could help scientists better understand how cells and bacteria detect and respond to changes in their surroundings.
The researchers’ mathematical model predicts another surprising consequence: the plant’s light-processing system may produce an effect resembling an optical illusion. Because the system responds nonlinearly to incoming light, the direction it effectively registers as brightest can differ slightly from the direction receiving the most illumination.
This does not mean plants see images or consciously misinterpret their surroundings. Rather, it describes a distortion in how their sensory system translates light into a growth response. The predicted effect was too small to measure directly in the experiments because of natural fluctuations in plant movement.
“What is fascinating is that plants can integrate complex information about their environment without a brain or central processing system,” said Prof. Yasmine Meroz, one of the study’s authors.
“The computation emerges from the way light is sensed and processed locally across the stem,” she said, adding that the principle could extend to cells, bacteria and other living systems that rely on distributed sensing.
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