Trees Have Their Own Version of Muscles, Study Finds

Nearly 15 years ago, scientists found that plants had a biological mechanism controlling their form that was once thought to exist only in animals. Now researchers from the same institution have shown how it works. Researchers from France's National Research Institute for Agriculture, Food and Environment (INRAE) and the University Clermont Auvergne have demonstrated that some trees use a version of a muscle to shape themselves as they grow.

To study this, the team placed young poplar trees horizontally, which caused them to curve upward toward the light. The curved trees were then set on a rotating platform inside a sphere lit from every direction, removing the influence of gravity on their growth. Over time, the trees pushed back against their horizontal positioning and gradually moved toward a vertical position as they grew.

On closer inspection, the researchers found the plants produced a specific kind of wood, which they call tension wood, on one side of the stem. This wood uses a push-pull motion to direct how the stem grows, acting like a muscle that drives growth upward. The tension wood eventually switches to the other side of the stem, so the two sides work like opposing muscles, similar to those seen in many animals.

"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. These findings therefore reshape more applied research aimed at improving wood quality and at obtaining trees that are as straight and as relaxed as possible, whatever life throws at them."

"Revealing the remarkable capabilities of trees requires a great deal of ingenuity," said Félix Hartmann, INRAE research engineer. "In this project, we achieved it by bringing together researchers from different disciplines, with complementary skills and perspectives." The research was published in the journal New Phytologist.