Researchers at INRAE have discovered that trees use opposing, muscle-like wood forces and an internal sense of body position to straighten their stems, challenging long-held assumptions about plant biomechanics. Science Daily reported that the findings reveal how plants coordinate growth through a newly identified sensorimotor loop, building on foundational work published in 2012.
How Scientists Isolated Trees’ Hidden Sense
Plants rely on multiple environmental cues to direct their upward reach, including gravity, sunlight, and the physical shape of their own stems. To study how trees monitor their posture independently, researchers designed an experimental system that removed external directional signals entirely. Young poplar trees were placed on a horizontal platform that rotated continuously around its axis. This apparatus sat inside a sphere illuminated equally from every direction.
The rotation neutralized consistent gravitational pull, while the omnidirectional lighting eliminated visual cues about vertical growth. By stripping away these environmental references, the team could observe how trees respond exclusively to their internal sense of shape, known as proprioception. Bruno Moulia, INRAE research director, explained that the work uncovers a genuine sensorimotor loop operating within woody plant tissues.
The Muscle-Like Wood That Helps Trees Straighten Themselves
The experiment began with young poplar trees positioned horizontally, causing their stems to curve upward over time. This initial bending relies on tension wood, a specialized tissue that generates pulling forces as it develops along the upper side of a stem, functioning similarly to a contracting muscle.
After ten days of natural curvature, researchers placed the curved trees into the rotating experimental apparatus. Over the following weeks, the stems slowly straightened out. Examination of the wood revealed that the original tension wood stopped developing once rotation began. Simultaneously, identical tension wood formed on the exact opposite side of the stem, acting as an opposing muscle to push the trunk back into alignment.
A Surprising Discovery About How Trees Control Their Shape
Before this study, published in Science and detailed by Science Daily alongside Europesays, scientists believed tension wood formed exclusively on the upper side of leaning stems. This asymmetric growth is commonly observed near the bases of trees on steep mountain slopes, where trunks must curve sharply to stay upright.
The new findings demonstrate that tension wood has a far more versatile role. It can develop on opposing sides of a stem and generate forces in multiple directions, mirroring the opposing muscle groups animals use to control movement and posture. Félix Hartman, INRAE research engineer, emphasized that revealing these capabilities required prolonged interdisciplinary collaboration.
Why This Discovery Matters for Forests and Agriculture
The ability to correct posture after severe environmental disturbances such as storms and landslides is vital for forest resilience, a trait that will likely become more critical as climate change increases extreme weather. In agriculture and forestry, understanding proprioception could allow scientists to select plant varieties that grow straighter and produce higher-quality timber by minimizing internal mechanical stress.
For crop production, the same mechanisms relate to lodging, a persistent agricultural problem where cereal plants collapse near the end of the season and reduce harvest yields. Controlling tension-wood formation helps researchers target these structural vulnerabilities.
Answers to Common Questions About Tree Proprioception
What is plant proprioception?
Proprioception is an internal awareness of body position and posture. While once thought unique to the animal kingdom, INRAE researchers demonstrated in 2012 that plants also possess this internal sense to monitor and adjust their shape.
How does tension wood work?
Tension wood is a specialized plant tissue capable of generating active pulling forces as it develops. Researchers found that this wood can form on opposing sides of a stem to push or pull a tree back into a straight vertical position.
What were the practical implications noted by INRAE?
According to INRAE research director Bruno Moulia, poorly coordinated tension wood creates excessive internal stress that degrades timber quality. Controlling these cellular processes could help forestry experts cultivate trees that remain straight and relaxed regardless of environmental stress.