Trees possess internal ‘muscle’ system to correct growth, study finds

Researchers have long known that plants respond to gravity and sunlight, but the biological processes enabling them to translate shape information into physical movement remained elusive. To isolate this internal sense, the team created a unique experimental setup. Young poplar trees were placed on a rotating platform within a sphere, eliminating directional cues from gravity and light.

During the experiment, the trees initially curved upwards as they grew. This curvature is driven by a specialized wood type called tension wood, which generates pulling forces. Initially, tension wood formed on the upper side of the stems, pulling them upwards. However, once the experimental apparatus was activated, the development of this tension wood ceased, and identical wood began forming on the opposite side of the stems.

This opposing tension wood effectively acted as a counteracting force, gradually straightening the stems. The team’s analysis revealed that this process involves a complex cellular-level regulation of tension wood formation. Previously, it was believed tension wood only formed on the upper side of stems to facilitate upward growth, particularly in trees on slopes.

This new research demonstrates a more versatile role for tension wood, enabling trees to generate forces in different directions, much like opposing muscle groups in animals. This discovery underscores a sophisticated system for coordinating growth, combining external environmental signals with an internal awareness of shape.

Understanding this mechanism is increasingly vital as climate change increases the frequency of extreme weather events that can damage trees. The findings also hold practical implications for forestry and agriculture. Identifying plants with enhanced proprioception could lead to the selection of straighter, more resilient tree varieties and improved wood quality. Furthermore, this knowledge could help develop cereal crops less prone to lodging, a common problem that reduces crop yields.

“What we have uncovered is a genuine sensorimotor loop operating in the woody parts of trees!” said Bruno Moulia, INRAE research director. “Poor coordination in the successive activation of tension wood results in excessive internal tension, which can affect wood quality.”

Félix Hartman, INRAE research engineer, emphasized the collaborative nature of the work: “Revealing the remarkable capabilities of trees requires a great deal of ingenuity. In this project, we achieved it by bringing together researchers from different disciplines.”,