Trees Use Muscle-Like Wood to Correct Their Growth, Researchers Find

Trees do more than passively grow toward the light. Research from France’s National Research Institute for Agriculture, Food and Environment (INRAE) and the University Clermont Auvergne indicates that young poplars can actively correct their posture using specialized wood that functions somewhat like opposing muscles. The researchers began by placing young poplar trees horizontally. The plants curved upward toward the light, as expected. The team then moved the curved trees onto a rotating horizontal platform inside a sphere illuminated from every direction. This arrangement was designed to remove gravity’s influence as a factor in the trees’ vertical growth. Even without that directional gravitational cue, the poplars gradually pushed back against their horizontal position. Over time, they moved toward a more upright form, suggesting that the trees were not simply responding to their surroundings but were also regulating their own shape. Closer examination pointed to tension wood, a particular type of wood produced on one side of the stem. According to the researchers, this tissue creates a push-pull effect that directs the stem’s growth. After beginning on one side, the process switches to the other, allowing the two sides to work against each other and help straighten the tree. The researchers describe this as a sensorimotor loop operating in the woody parts of trees. The mechanism is distinct from the role of cell turgidity, which is already known to influence plant form, and appears to require significant energy. Bruno Moulia, an INRAE research director, said the findings could inform research focused on wood quality and on producing straighter trees. Poor coordination in the successive production of tension wood, he said, can create excessive internal tension in the tree and affect the resulting wood. The work also adds to an evolving picture of plant behavior. Plants are already known to adjust growth in response to light and to cope with challenges including salinity, limited nutrients and pathogens. The study, published in New Phytologist, indicates that some trees have a more active role in shaping their structure than previously recognized.