A tangential line of interest for me is the occurrence of some parasitic fungi on my aquatic plants. These organisms have evolved into a highly sophisticated relationship to their hosts, wanting to be supplied with all ingredients required for their own existence and propagation, but not to an extent that kills all potential hosts. So there is a delicate balance in play here. In our Covid-19 impacted times it bears in mind that the entire biosphere handles a myriad of such balancing acts between parasite and host. The C-19 virus is just one species with a transient impact span within the individual host. The fungi on aquatics typically are stenophagous, i.e. only occurring on a few related host plants. Thus they can be of assistance in determining host ID, or even used for biological control of their host(s).
Oh well. This summer I had smut fungi of the genus Doassansia on my short list as this genus specialises on aquatic plants. Of the 3-4 species likely to be found in Norway, D. sagittariae apparently is the most ubiquitous. It parasitises only Sagittaria spp. and in my country, only Arrowhead S. sagittifolia, which has a limited distribution within Norway. Fortunately I'm located at the "epicentre" of its distribution. So I battled against blood-thirsty midgets, mosquito, horseflies, and sundry other environmental pests in order to collect my smut fungi samples the last few days.
The Arrowhead Smut infests the foliage, either aerial leaves or floating leaves, to make circular discoloured leaf spots. Within the centre of the spots one can with the naked eye just barely recognise darker patches which are light brown spore balls with hundreds of smut spores enveloped by sterile hyphae. The spore balls being embedded into the plant tissue presents a challenge if you wish to photograph them, as the overlaying tissue of course smears everything. You can see them, but there is no detail at all, just a shaded outline.
People knowing me know I am fond of challenges, so here is what I did: First, insert a leaf with smut infestations into boiling water for 30 secs. This will stop any photosynthetic activity. Then, using a water bath, boil the leaf in 70% IPA (I reserve ethanol for private consumption so isopropyl alcohol has to do) for 5 minutes, rinse in hot then cold water 3 times, soak in 5% sodium hypochlorite for 10 minutes, rinse 3 times using hot water, dry sample and examine whether it stills smells of bleach, if so repeat rinsing until there is no foul odour. Finally add Acridine Orange dye in 2% acetate and let it stand overnight. Next day, rinse in water until no colour dye leaks out, then boil in 70% IPA for 3 minutes, rinse 3 times in water. The sample should now be almost colourless but with an orange hue to it.
Using a Convoy UV LED torch (365nm) for illumination, the spore balls now had a beautiful UV-induced (UVIVF) fluorescence and showed a lot of detail. Even the individual spores of the outer cortex layer were immediately visible. The spore balls are up 50-80 um in diametre, thus thinner than a Nordic hair and the individual spores are approx. 8-9 um.
Camera: Z7, Mitutoyo 10x objective, Convoy UV-LED 365. The scale bar of the cropped image shown below is 1mm.