Nearly 15 years ago, scientists found that plants had a biological mechanism that controls their morphology – or, in simpler terms, their form – thought to have only been something seen in animals. Now, researchers from the same institution have uncovered how it works. It's basically a tree's version of a muscle.
Researchers from France's National Research Institute for Agriculture, Food and Environment (INRAE) and the University Clermont Auvergne have demonstrated that plant growth and survival are more complex than previously realized.
While already known to have strategies to optimize light exposure and have a myriad ways for dealing with salinity, nutrient-poor soil and pathogens, scientists have now shown that some species use their version of a muscle to shape themselves, revealing that it isn't just a natural part of growth but a strategic and energy-intense mechanism to give them the best chance of survival.
To isolate this sense, the team designed an experiment with young poplars. First, young trees were placed horizontally, causing them to curve upward toward the light. The curved trees were then placed on a horizontal rotating platform inside a sphere lit up from every direction. The main idea was to eliminate the role gravity – a key factor in vertical growth – plays.
What they found was that, over time, the young trees pushed back against their horizontal positioning, gradually moving toward a vertical position as they grew, appearing to self-correct and develop a kind of "posture" in its form.
On closer inspection, the researchers found that the plants were able to produce a specific kind of wood – which the team calls tension wood – on one side of the stem that uses a push-pull motion to direct the way the stem grows. Essentially, it acts like a muscle that drives growth upward.
"What we have uncovered is a genuine sensorimotor loop operating in the woody parts of trees," says 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.”
We recently covered how narwhals possess the only straight tusks in the animal kingdom. It turns out these particular trees have a similar process involving chemistry and biomechanics that drives their straightness. While that tension wood on one stem side begins the process, it eventually switches sides, essentially working to straighten the poplar plants' structure.
Basically, the two sides of the tree's stem worked like opposing muscles – the kind we see in many animals – and something that has nothing to do with plant cell turgidity that we know plays an important role in the morphology of flora.
“Revealing the remarkable capabilities of trees requires a great deal of ingenuity," adds Félix Hartmann, INRAE research engineer. "In this project, we achieved it by bringing together researchers from different disciplines, with complementary skills and perspectives. This requires time and perseverance, but these interdisciplinary discoveries show that the effort is worthwhile.”
So, why should we care, when nature is commonly viewed through an economic-value lens? Well, this study shows that learning about proprioception could help us get rid of "plant blindness" – which ultimately benefits us, too.
And it shows that you don't need to be a scientist to bring about change. As this 2025 study revealed, people who put their photos on iNaturalist contributed to at least a dozen new species being identified. Much like our understanding of plants, the value of citizen scientists is undervalued and so desperately needed.
The research was published in the journal New Phytologist.
Source: INRAE via EurekAlert
