Trees use a 'muscle' to correct their posture—a newly discovered role for tension wood

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A research team from INRAE and the University Clermont Auvergne has shown that trees are capable of correcting a curvature they detect in their stems through a specific biological process. In the study, young trees with bent stems were placed in an experimental set-up that prevented them from sensing their orientation relative to light and gravity.

The only sense remaining to the trees was the perception of their own curvature. Under these conditions, the scientists observed the formation of a particular type of wood, known as tension wood, which acts like a muscle to correct the curvature of the stem, allowing it to realign within a few weeks. Published in New Phytologist, the findings show how plants—under natural conditions—finely perceive their own shape and combine this information with signals relating to their orientation to adjust their posture.

This ability plays an important role in their resilience when faced with extreme events such as storms or landslides. Proprioception is the sense through which living organisms perceive the position of their body parts, and it was long believed to be specific to animals. In 2012, a research team involving INRAE demonstrated that plants also possess this ability.

This enables them to control their posture and remain as straight as possible. However, the biological mechanism governed by this proprioception remained unknown. Plants orient their growth in response to factors they perceive, including gravity, the direction of incoming light and their own shape, that is, proprioception.

To investigate proprioception on its own, all other sensory inputs must be eliminated. To remove the sense of gravity and the influence of light direction in trees, the scientists placed the specimens under study in a specially designed experimental setup: a horizontal platform rotating around its own axis inside a sphere flooded with light coming simultaneously from all directions. The researchers first placed young poplar trees in a horizontal position.

Over time, the trees curved upward, bringing their tops back to a vertical orientation. This movement is driven by a particular type of wood: tension wood. It acts like a muscle that, by contracting, exerts a pulling force on the upper side of the stem, causing it to bend upward.