Light doesn’t just help plants grow, it also strengthens their internal structure by tightening the connection between tissues. This added rigidity can actually slow growth, revealing a hidden balance between strength and expansion.
Light is widely recognized as a key factor in plant growth, but scientists are still uncovering the details of how it works. Researchers at Osaka Metropolitan University have now identified a previously unknown process that helps explain how light influences plant development.
Light Increases Adhesion Between Plant Tissues
The study, led by Professor Kouichi Soga from the Graduate School of Science, focused on young pea stems. The team developed a specialized technique to measure how strongly the epidermal (the outermost layer) is connected to the inner tissues. Their experiments showed a clear difference depending on whether the plants were grown in light or darkness.
Plants exposed to light had significantly stronger adhesion between these layers compared to those grown in the dark.
“Compared with plants grown in the dark, the epidermal and inner tissues of plants grown in the light are more tightly bound together,” Professor Soga said. “This phenomenon has never been reported before, making it a particularly interesting finding.”
p-Coumaric Acid Strengthens Plant Cell Walls
To investigate the cause of this effect, the researchers examined the plant cells using a fluorescence microscope. They observed that stems grown in light produced signals indicating higher levels of a phenolic acid known as p-coumaric acid.
This compound plays a role in reinforcing plant cell walls, which helps increase the strength of the connection between tissues.
“This provided strong evidence that the accumulation of p-coumaric acid was a key factor in strengthening the adhesion between the epidermal and the inner tissues,” said Yuma Shimizu, a graduate student and first author of the study.
Stronger Adhesion Can Limit Plant Growth
The findings reveal that this increased adhesion has a direct impact on growth. While stronger connections improve structural integrity, they also make it harder for the inner tissues to expand.
As a result, overall stem growth is reduced. This suggests that light not only supports plant development but can also restrict it by tightening internal structures.
Implications for Plant Growth and Crop Resilience
The researchers believe this mechanism could be part of a broader pattern in how plants regulate growth. By continuing to measure adhesion under different conditions, they aim to determine whether this process applies widely across plant species.
“By measuring the adhesion between the epidermal and the inner tissues as stem growth changes in response to various factors, we expect to determine whether growth regulation mediated by changes in adhesion is a universal mechanism,” Professor Soga concluded. “These findings could be highly significant for plant cultivation. If we can control adhesion, it may be possible to breed plants with improved tolerance to environmental stress.”
The findings were published in Physiologia Plantarum.
Reference: “White Light Enhances Adhesive Strength Between Epidermal and Inner Tissues of Pea Epicotyls via Accumulation of Cell Wall-Bound p-Coumaric Acid” by Yuma Shimizu, Kazuyuki Wakabayashi, Kensuke Miyamoto and Kouichi Soga, 25 January 2026, Physiologia Plantarum.
DOI: 10.1111/ppl.70755
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