Guttation

Day 344: Why do some fungi sweat? The phenomenon is most often seen in polypores (shelf fungi), but occurs in a few other species as well. In vascular plants, guttation happens when root pressure and high humidity combine. In fungi, it's not as well understood. Some studies suggest that the fungus is ridding itself of excess moisture which otherwise might cause it to rot. Others have shown by chemical analysis of the exudate that it may contain bioactive compounds, some of which could be harmful to the fungus, and by "sweating," it is expelling them. Conversely, it is also known that fungi may also reabsorb beneficial nutrients held in guttation droplets. The best time to observe guttation in plants or fungi is on a high-humidity morning following a cool night, and now that the Pacific Northwest has returned to its autumn weather pattern, you should have plenty of opportunities to find fungus sweating in the forest.