Pine cones open when dry and close when wet. In this way, pine seeds are released only under advantageous conditions, namely when it is dry and the seeds can be carried far by wind. Opening and closing is of particular interest to researchers because the actuation is passive, that is, it does not consume metabolic energy. This is why the pine cone has already served as a model for biomimetic flap systems that react to moisture and are used, for example, in building envelopes to regulate the climate. https://www.sciencedaily.com/releases/2022/05/220531122100.htm
