Read It and Weep: Fungal Guttation

by Jan Thornhill

Young Red-Belted Polypore (Fomitopsis pinicola) with guttation drops

Some fungi are prone to exhibiting a curious phenomenon—they exude beads of moisture, called guttation. In several polypores, such as Fomitopsis pinicola, the liquid produced can look so much like tears that you'd swear the fungus was weeping. Or maybe sweating. Other species produce pigmented drops that can look like milk, or tar, or even blood.

Guttation is more well-known in some vascular plants. During the night, when the plant's transpiration system is shut down, pressure from excess moisture in the roots can force beads of sap out of special structures on leaf edges. 

Guttation droplets on strawberry leaves (Noah Erhardt/Wikipedia)

In fungi, the guttation mechanism is not so well understood. In many species, however, it's so often observed, particularly during times of rapid growth when temperature and humidity are favourable, that these beads of liquid can be a reliable macroscopic characteristic. Hydnellum peckii, for instance, so frequently "bleeds" pigmented drops in its early stages of growth that it's been given gruesome nicknames, including "Bleeding Tooth Fungus" and "Devil's Tooth." Coincidentally, a 1965 study found a compound in the fruiting body of  H. peckii that has anticoagulant properties similar to those of heparin, too much of which can make one bleed to death internally.   

Bleeding Tooth Fungus (Hydnellum peckii) produces red-pigmented 
guttation droplets during periods of rapid growth. (Lisa Neighbour)

A couple of years ago, I came across a crop of Inonotus glomeratus on a maple log. I'd found this amazing polypore a few times, once right after it had showered itself, and everything else around it, with millions of sulphur-yellow spores. The one I'd found, though, was very young, and instead of spewing spores, it was weeping globules of "tar" in copious enough amounts that shiny black pools were accumulating on the forest floor. Unlike most guttation drops, which are watery, these exudations were thick and sticky and stained my finger and thumb a deep auburn brown. And kind of glued them together. Oddly, though this unusual guttation has been noted by others, there seems to be no mention of it in the literature. I. glomeratus is so unusual in so many ways, I ended up writing a whole post about it.

Fast-growing Inonotus glomeratus produces tarry guttation.

This Inonotus glomeratus continued to drip its viscous black exudate
even after it began releasing its yellow spores.

The guttation drops on this Inonotus glomeratus were so thick that the fungus grew
around them, producing a pitted appearance after rain washed them away.

Polypores and Hydnoids are not the only fungi to produce guttation. In moist conditions, young Suillus americanus stipes can be heavy with yellow-tinted drops. Guttation is also common enough in the uncommon Rhodotus palmatus that this characteristic is often included in descriptions. 

Chicken Fat Suillus (Suillus americanus) 

Wrinkled peach (Rhodotus palmatus) 

Guttation can happen in incredibly small ways, too. During the Toronto Bioblitz a few years ago, we found some Lachnum subvirgineum that, despite what seemed like dry conditions, were covered in minute guttation droplets, as were most other Lachnum I've since come across. 

The largest of these Lachnum subvirgineum was less than .5 mm. in 

diameter, which makes the guttation droplets impressively small.

Another minute character is so characteristically bejewelled in guttation droplets, it's named for it: Pilobolus crystallinus, which is one of the "Cannon" or "Hat Thrower" fungi found on herbivore dung.

Dung-loving Pilobilus crystallinus, is named for its sparkling
guttation droplets. (See my post about this remarkable,
tiny fungus, also called Hat Thrower, or Cannon Fungus)

Though little is known about guttation in wild fruiting bodies of fungi, it's a common phenomenon of fungal mycelia and hyphae in the lab, and a number of studies have been done to determine what the exudates contain. Penicillin has been found in the guttation droplets produced by Penicillium species in similar concentrations to that found in the culture broth, while gliotoxin, which has immunosuppressive qualities, has been found in guttation droplets of Aspergillus fumigatus. Do these fungi use guttation droplets as reservoirs for metabolic byproducts, or do they simply use them for water storage? 

Or have different species evolved to produce guttation droplets for different purposes? The edible bolete, Suillus bovinus, for instance, has been shown in the lab to reabsorb nutrients from its guttation droplets, while leaving behind less useful byproducts, such as oxalic acid. So perhaps guttation has evolved as an efficient method of expelling waste for some fungi. 

Is that what's going on with Inonotus glomeratus? Is that viscous, black ooze just a collection of rejected metabolic byproducts? If anyone would like to analyze it and has the means, I have some dehydrated exudate that I'd love to send you!  

Even some slime moulds, like this immature Stemonitis 
flavogenita, produce guttation droplets. (Ulrike Kullik) 

Pink-pored Fomitopsis rosea are even prettier when 

decorated with shimmering beads of moisture. I think the 
pattern on rim was made by the "teeth" of a grazing slug.

Tree Bacon (Punctularia strigosozonata) "bleeds" rust-tinted droplets.

Early nubbins of an unidentified polypore exude milky drops.

This Red-belted Polypore (Fomitopsis pinicola) produced guttation 
droplets for three months one summer. When it finally stopped, 
trompe l'oeil teardrop-shaped indentations were left behind.

Wet weather makes Xylaria hypoxylon produce beads of moisture.

This large Pleurotus dryinus was weeping copiously
despite there having been no rain  for a week.

Many parasitic Hypomyces, such as this H. chrysospermus, are prolific weepers. 

Inonotus dryadeus is a lumpy polypore known for its ample
 production of amber guttation droplets. (Wikipedia)

The Jack-o-lantern Mushroom (Omphalotus illudens) not only
glows in the dark, it also produces orange-staining guttation.

The Resinous Polypore, (Ischnoderma resinosum), is also named
for the droplets it produces when very young.

The reddish-rimmed gills of this group of Mycena
leaiana produced tiny white droplets. 

Even the hairy asexual form of Postia ptychogaster produces guttation.

Selected References:

Erast Parmasto, Andrus Voitk, (2010). Why Do Mushrooms Weep? Fungi, Vol. 3:4

Hutwimmer, S., Wang, H., Strasser, H., Burgstaller, W. (2010) Formation of exudate droplets by Metarhizium anisopliae and the presence of destruxins.Mycologia, Vol. 102 no. 1, 1-10

Gerhard Saueracker. On the Exudates of Polypore Fungi. Fungimap Newsletter 48, Jan. 2013

(NB: This is a slightly edited repost from my other blog: Weird & Wonderful Wild Mushrooms

Bioblitzing: A New Outdoor Entertainment

by Jan Thornhill

A bit more than a month ago my friend Tony invited me to help with the fungi portion of the 2014 Ontario Bioblitz.

"Bioblitz?" I said. "What the heck is a Bioblitz?"

When documenting fungi for a Bioblitz, you document all fungi, like this
Rhytism americanum, a tar spot that attacks native maples. 

A Bioblitz, it turns out, is a pretty cool event. It's an intense 24-hour study of a specific area's flora and fauna during which professional biologists lead teams that document all the living things they can find. It's essentially an exercise that highlights biodiversity. Though ornithologists and entomologists worked through the night looking for owls and moths and other nocturnal critters, since I was working with the fungi team, led by Jean-Marc Moncalvo, Senior Curator of Mycology at the Royal Ontario Museum, and fungi don't move around a lot, we didn't have to forgo sleep and focussed on collecting samples when they were visible—during daylight hours.

A fresh specimen of Gloeoporus dichrous. During the Bioblitz,
we only found a dried up one from the previous fall.

Bioblitzes are a perfect introduction to citizen science, since the public is usually encouraged to help. This year's May 25 event was focussed on the Humber River Watershed. There were lots of activities, including guided walks with professional biologists, batbox-making workshops, and field-sketching workshops. But the main event was documenting species, and the main event was wonderfully successful. From the 24-hour period, a total of 1,563 species have been identified so far, including 109 arachnids, 121 birds, 27 fish, 500 insects, 100 non-insect invertebrates, 18 reptiles, 94 lichens, 21 mammals, 78 mosses, 450 plants, and 45 fungi.

That's a millimetre rule behind these fuzz-covered Lasiosphaeria ovina.

The fungi numbers were low—we only found about half the number of species documented on each of the first two Ontario Bioblitzes in 2012 and 2013, but we have an excuse: May 25 is never a prime fungi-finding time, on top of which there'd been almost no rain for two weeks.

The honey locusts growing in our Bioblitz fungi-hunting area were treacherous! 

Undeterred, Tony and I explored a scrubby woods not far from the McMichael Gallery parking lot. It was so dry that, at first glance, it looked as if we weren't going to find anything at all other than a few gnarly, desiccated, insect-ravaged tree-growing fungi from the previous fall (they still counted, though!). But once we got down on our hands and knees, (and wiped off the blood from being stabbed by the wicked thorns of honey locust trees), and started turning over fallen branches, we found a few interesting specimens. Admittedly most of these were tiny interesting specimens, but they included some exquisite, snow white, mini stemmed cups bejewelled with dew, and a quite beautiful parasitic rust fungus (featured in my fungi blog post, here), as well as a single, charismatic, and delectable, morel. 

We had to use a microscope to nail down the identity 
of these half-millimeter beauties, Lachnum subvirgineum.

It was fun. It's always fun looking for fungi. It's like a treasure hunt. So I was delighted to get an invitation to attend another Bioblitz. This one is at the Alderville First Nation Black Oak Savanna, located southeast of Rice Lake. The savanna is very special place, Canada's easternmost prairie habitat and one of the most endangered plant communities in Ontario, where the primary goal is to restore land that has previously been used for agriculture by planting and nurturing native tall-grass prairie species.  

Because there are a number of species at risk at the Alderville Black Oak Savanna site, this Bioblitz is not geared towards the public's participation in the same way that the much larger Ontario Bioblitz is, but if you'd like to visit the site you can book a tour by calling 905-352-1008. They also have programs and resources for schools, as well as an annual eco-friendly "Prairie Day," which, this year, is on Saturday, September 10. 

*You can read about a few interesting things we found during the Alderville Bioblitz on my Weird & Wonderful Wild Mushrooms blog.