Why do mushrooms weep?

Erast Parmasto1 2 & Andrus Voitk contact with colder surfaces, accounting corticioid and many bracket fungi, as for frost on clothing and hair during well as some stipitate hydnoids, but subzero weather. The amount of frost relatively uncommon among gilled ll life is energy dependent. Most increases if we increase our metabolic fungi and boletes, excepting a few Suilli. large multicellular organisms rate by physical activity (Figure 1). Differences in handling excess water by break down their food into Carbon dioxide and water are genetically different fungi should not be simpleA sugars, which are used to release metabolic products for many fungi surprising, because chemical reactions the energy required for life. This is the as well, which several exude invisibly directing physiological pathways are catabolic part of metabolism. Its other from their surface. During periods of genetically programmed. An interesting end products, if following an oxidative rapid growth, metabolism speeds up. example of this might be provided by pathway, are carbon dioxide and water. In those periods some mushrooms the familiar Fomitopsis pinicola. In We breathe out not only carbon dioxide, form visible drops on their surface. Estonia it is common for this polypore to but also a large amount of water as a weep weakly acid water during growth gas into the atmosphere. This is why (Figure 2). In Newfoundland guttation we can see our breath on cold days: the by growing F. pinicola is uncommon. warm water vapor condenses on contact Breeding studies suggest that F. pinicola with the colder outside air, and becomes is a species complex of at least three visible as a cloud of small water droplets. morphologically similar species, one in On really cold days these droplets freeze Europe and two in North America. Is it into solid ice when they come into possible that the genetic programming for guttation is present in the European species, but not in that found in Newfoundland? Guttation may provide macroscopic means to differentiate some cryptic species.

Figure 2. Rapidly growing very young fruitbody of the European Fomitopsis pinicola, showing copious water droplets; Kesselaid Forest, Estonia. Photo: Kristiina Veltmander. Guttation is characteristic for this species in northern Europe, but not in Newfoundland. Figure 3. Actively growing This is called guttation, a term used with red droplets; in botany to describe the process by Gros Morne National Park, which plants excrete excess water through drops from their leaves. For Newfoundland and Labrador, Figure 1. Water from breath, settling some mushrooms this is so common Canada. The light color and soft as ice crystals on clothing and hair that it is a reliable identification feature, texture of the fruitbody indicates after skiing for two hours at -47°C; while for others it is virtually unknown. that it is actively growing. Inuvik, NWT, Canada. Guttation is common among several Continued on page 16. FUNGI Volume 3:4 Fall 2010 15 Figure 4. Actively growing Hydnellum multiceps; Gros Morne National Park, Newfoundland and Labrador, Canada. Again, the light color and soft texture of the fruitbody indicate that it is growing rapidly.

Hydnellum peckii is well known for 4). Most guttating mushrooms produce Just as we make frost when exhaling its droplets (Figure 3). These are usually clear droplets, often more viscid than water vapor in subzero air, rapidly colored red by terphenylquinone (or water, suggesting that they also excrete metabolizing mushrooms that have a derivative), a pigment produced by this other chemicals. Thus, under the right developed during periods of winter of mushrooms. Under favorable conditions Stereum sanguinolentum thaw can also form ice under certain temperature and humidity, red droplets forms copious clear droplets (title temperature fluctuations. As the air can also be seen in other members of banner); although it contains red latex, cools after sunset, metabolism slows the genus during active growth (Figure the pigment is not exuded with guttation. down. The mushroom’s surface cools

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16 FUNGI Volume 3:4 Fall 2010 little evaporation, and as the temperature andas little evaporation, there is aircools, as saturation increases athaw during humidity high is and Because surface. contact this cooler with might condense to liquidwatervapor on continues inthe core, exuded water core metabolism its before andifsome underside and a 20% rim of the upper surface. ofthe upper anda20%rim underside oficeand Labrador, covering Notethin sheet Canada. Humber Village, morning; February early Newfoundland Figure 5.Young onan photographed americana Auricularia QuarterPageFungiMag 11/3/108:54AMPage3 T H C I T S I R M A S U R U G M O O R H S U M R E H C A E T o E C O L O G I S T · E N T O M O L O G I S T · or 18” der posters: der Proceeds benefit Sam Ristich Archive Fund Archive Ristich Sam benefit Proceeds X 24” · $25 $25 · 24” · R O T N E M D E M A R F N U www .samristich.com · · · TURALIST S I L A R U AT N A R O VAT I T O M $ has not been confirmed confirmed notbeen has relationship acausal albeit well is known, growth rapidphenomenon with ofthis the association droplet formation, but for may many reasons be 115

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· T S I N O I T A V R E S N O C R E H P A R G O T O H P been done.There been has guttation fungal investigation of ice (Figure 5). toenough melt the the air warmed thebefore sunhas the morning, early in documented be can This freezes. the water freezing, below drops Very little Labrador, Canada Humber Village, and Newfoundland Tartu,Sciences, Estonia.) University Estonian ofLife Sciences, andEnvironmental of Agricultural explanation, tested. inviting to be rate offers a felicitous andplausible metabolic the water to anincreased Inthe interim, ascribing unanswered. ofthe considered titlequestion must be scientifically. the Without such studies, 2 1 Foray &Labrador, Newfoundland ofMycology,Department Institute FUNGI Volume 3:4Fall 2010

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