As shown in the movie below, pinecones close when wet, and open again when they dry. But pinecone scales are made up of dead cells, which means their movements must be a mechanical response to getting wet. These scientists used a variety of imaging techniques, including X-ray tomography, to figure out how pinecones open and close in response to water. They found that pinecones direct water that lands on the outside "bract" scales towards the inner scales which respond and cause the cone to close before the whole pinecone gets soaked. This ensures the pinecones release seeds on dry days, giving the next generation the best shot at a wide dispersal. Treegonometree in action!
Journey of water in pine cones
"Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system."