Pd/UV Spot Tests
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February 3, 2019 at 11:01 pm #31206
Mark Have you tried this one?
Taking a break from DIY, just before it was dark, I had quick look around a local New Forest wood, French’s Wood, which is part of the Shave Wood complex, an exceptionally richen rich old growth Beech – Oak pasture woodland. One suppressed Oak had a bit sheet of what looked like slightly wrong
Denderographa decolorans( Schismatomma decolorans), so was potentially Syncesia myrticolasorediate morph ( Enterographa sorediata), which has protocetraric acid. To test this I put some Pd spot tests on the thallus but nothing much happened. As it was freezing and Pd is slow in these conditions I wandered off for a bit and then came back and yes a rather pale and patchy orange reaction so certainly not Denderographa decolorans. A patchy variable reaction is typical of Syncesia myrticolasorediate morph, so was probably that. I then thought to shine the UV touch on it; the areas with the reaction shone out brightly with UV fluorescence, the same colour as the reaction. Nearby a convenient near by sterile Cladoniasomething or other gave a typical strong Pd + orange-red spot test (fumarprotocetraric acid), which also shone out with UV fluorescence, again the same colour as the spot test reaction. Similarly some of the ubiqetous Snippocia nivea( Schismatomma niveum) gave a strong Pd yellow reaction (psoromic acid), which was, you guessed it, had bright yellow fluorescence. Both these Pd reactions were quite rapid, so the slow first reaction was probably due to low levels of the acid in the thallus as much as the cold. Not sure any of this is diagnostic, but rather like the K/UV atranorin test (bright yellow fluorescence) looks to be useful in confirming a reaction has occurred when the acid is present at low levels in the thallus.
Some pictures below
All the best
Neil
February 4, 2019 at 10:02 am #41793Hi Neil, Many thanks for these observations. I haven’t got far with investigating Pd/UV reactions except to notice, as you have done, that sometimes a bright fluorescence is seen. This is not the Pd fluorescing (in case anybody wondered) because Pd on an inert, non-fluorescent surface gives a weak mauve fluorescence. I have noticed a Pd/UV+ yellow-orange fluorescence with Pertusaria amara so presumably that was due to the presence of protocetraric acid.
Even if the subtleties of different Pd/UV+ colours are not diagnostic, this could still be very useful (as you suggest) to detect whether any reaction has taken place. I sometimes find it difficult to judge on these Trentepohlia-containing crusts, whether I am looking at a weak Pd+ reaction, or the dull orange of the photobiont showing through, or just the staining from some slightly discoloured Pd solution.
Even if this phenomenon merely shows presence or absence of a Pd reaction, that would be very useful. Chaenotheca stemonea?
Andre Aptroot provided a trial for the K/UV test with some blind specimens that he had previously analysed by tlc. Unfortunately the results were not a perfect match. This is a bit frustrating/interesting/puzzling but I still think that X/UV has value.
Mark
February 4, 2019 at 9:53 pm #41794Mark Yes Andre said he had sent you a test at the BLS field meeting at Painshill, I hope the complications can be worked out! I was able to use a positive K/UV test to confirm some sterile
Lecanographa lynceamaterial on an old Oak there. I would have called it that anyway, but the strong K/UV mauve fluorescence ruled out Lecanographa amylacea, I hope. I have also just got a negative K/UV test from a scrap of apparent sterile Lecanographaspecies I collected from an old Oak in Mark Ash Wood on the Wessex Lichen Group visit a couple of years ago. It is an easily accessed tree, so I will get some more soon and recheck this too. I tried the Pd/UV test on some more
Syncesia myrticolasorediate morph on the underside of an old Oak in dark, miserable and very humid conditions in Shave Wood this lunch time. One patch was apparently full charged with protocetraric acid and gave a good strong orange-red reaction, which was obvious (and fluoresced orange-red) but a second bit of the same thallus had a week and yellowish Pd reaction and was difficult to see with the damp conditions, but was easily confirmed by the yellow-orange UV fluorescence. So yes the Pd/UV looks good for amplification of week tests. Also tested serval non Pd reacting lichens, which did nothing with this test. I was interesting to see the amount of dew precipitation on the lichens on the dry over hanging side of the tree,
Sporodophoron cretaceum( Schismatomma cretaceum) in particular was holding on to great globs of dew; in the majority of its habitats it probably gets most of its water by the precipitation of dew. Admiring this, I was pleasant surprised to spot some of the short stalked pinhead Chaenothecopsis retinensparasitising the Sporodophoron cretaceum; second New Forest record, sixth modern British site, seventh modern world record and eighth record ever (I think). Anyway my strike rate for this has gone from once every 10 years to about once every 6 months (some pictures from the first Forest record attached, worth looking out for as black hemispheres poking out of Sporodophoron cretaceum). All the best
Neil
February 5, 2019 at 8:46 am #41795On the subject of UV tests, I have been asked by several people about effective eye protection. The cheap glasses I bought didn’t work. Do you have make and model of the ones you use handy? Thanks,
Mark
February 5, 2019 at 9:20 am #41796Yes the Convoy S2+ torches we use now are dangerously powerful, and require safety glasses Buy from a reputable source, such as a DIY supper store; 100% UV protection safety glasses are about £4.50 in B&Q. Test the glasses with your UV light by holding a piece of white paper or your finger nail where your eyes would be and turn on the torch. It will be obvious if the glasses work! See pictures. You can also do this check in the shop, the cheapest glasses in B& Q where not even in packaging
I use these industrial safety glasses in the lab, but use a pair of 100% UV protection swimming googles in the field as they fold down easily into a pocket.
Also in the field your finger nail is a good reference subject to test your battery power, do not look into the light!
Neil
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