Bent Trees With No Sense of Up Straightened Themselves

A young poplar with a curved stem, rotating inside a sphere lit from every direction at once, had no means of telling which way is up. It straightened regardless, in a matter of weeks, by growing a kind of wood that pulls.

Researchers at the University Clermont Auvergne and INRAE were after proprioception, the sense by which an organism tracks the position of its own parts. It was long assumed to belong to animals alone, until a 2012 study showed that plants have it too. The biological machinery it controls stayed unknown.

So the team laid young poplars on their sides. The trees bent skyward by forming tension wood along the top of the stem, a tissue that contracts and hauls the stem toward it, much as a muscle would. After about 10 days, the curved trees were moved onto a horizontal platform spinning on its axis inside the sphere. That removed any cue from gravity or from the direction of light and left the trees only their own bend to sense.

The tension wood on top stopped forming once the device was running. A wood matching it in every anatomical respect grew along the opposite face of the stem, where it appears to work as an opposing muscle, pulling the stem back to straight.

Until this study, tension wood was understood to grow only along a stem's top and only to bend it upward. The team says the ability contributes to how well trees hold up when storms or landslides shift them out of position. Bruno Moulia, an INRAE research director, said the applied aim is trees that grow straight and stay relaxed.

The poplars had weeks in a sphere with no up. For the record, nobody told them to sit up straight.

Read the full story at INRAE, September 2, 2026

Hot Take: The funding line names the French National Centre for Space Studies. A tree that corrects its posture without gravity's advice is apparently of professional interest where gravity is scarce.