Trees appear to use tension wood to straighten their stems

Trees may have a built-in way to sense and correct their own posture, according to research from INRAE and the University Clermont Auvergne reported by Phys.org. The study focused on tension wood, a specialized form of wood known to develop in certain parts of a leaning stem. Researchers found evidence that it can act in opposing directions—much like an internal muscle system—helping a tree both change its angle and straighten itself. To isolate the trees’ ability to sense their own shape, the scientists used young poplar trees and a specialized rotating platform inside a sphere illuminated equally from all directions. This arrangement removed the usual directional cues from gravity and light. The remaining information available to the trees was the curvature of their stems. The researchers first placed the young trees horizontally. Over time, their stems curved upward, bringing the tops back toward a vertical position. This movement was associated with tension wood forming along the upper side of the stem, where it generated a pulling force that caused the upward bend. After roughly 10 days, the partly curved trees were placed in the experimental device. Over the next several weeks, their stems gradually straightened. Examination of the newly formed wood showed that the earlier tension-wood production on the upper side had stopped. Instead, similar wood developed on the opposite side of the stem. According to the research team, this opposite formation appears to produce a counteracting force, progressively bringing the stem back toward a straight shape. The finding adds a newly described role to tension wood, which had generally been associated with upward bending, including in trees growing on mountain slopes. The study builds on earlier work showing that plants possess proprioception—the ability to perceive the position or shape of their own bodies—a capacity once thought to belong only to animals. The researchers say trees combine this internal information with environmental signals such as gravity and light to regulate their posture. The findings, published in New Phytologist, may also matter for forestry and crop research. The team said that understanding how trees coordinate tension wood could help efforts to improve wood quality and select plants that remain upright, including crops vulnerable to lodging. Poor coordination in the process can create excessive internal tension in wood, according to the report.