Sporangia

Looking for unopened sporangia – (these are the structures that contain spores and can be found on ferns and other plants) – I found them at the end of my holiday in a tropical country. The climate there allows development of sporangi allthrough the year. Ferns were abundant over there, and I was able to find many different variants. Back home it was fun to observe them with a fluorescence microscope (Lomo, type Lumam R1) utilizing ultraviolet excitation.

I noticed many differences in size, colour of radiated light, size of sori and how populated on the leafs. For example, the sporangi in photo 6 were exclusively covering the outer edge of the soft finger shaped leafs.

To make a start with photo 1 to 3: these show a not yet identified plant with long flat yucca-ish leafs. The sporangia were on the backside in a square pattern.

Photo 1 and 2 with (approximately) 7x objective and respectively the green and blue filter block. (merged from 2 stacks) Photo 3 the same but with 9x objective. The remaining pictures were also taken with the 9x. Photo 4 and 5 are from one of the ferns, you can see some sporangia cracked open. Photo 6 and 7 are from above mentioned sample, with radiation colour more purple and blue.

The next challenge was to work with higher magnification. Lomo manufactured a standard set of M27 epi objectives with 9x, 21x, 40x and 95x magnification. Besides that there’s the “old” set of M27 epi objectives that are longer and haven’t got the magnification engraved, but the Na and the focal length. Because somehow the 21x objective did not provide the expected detail, I switched over to the F 8,2 / Na 0,37 objective. Based on the Na the expected magnification would be 18x, when compared with a calibration slide it appears to be 22,5x. In my opinion this worked out better than the 21x objective, see below photo 8

Next, I’ve kept a couple of interesting samples in FAA (Formalin-Alcohol-Acetic Acid), with the idea to keep the preserved for years. Unfortunately by killing in fixative the sporangi opening reflex (activated by light) was not eliminated; after removing the item from the fixative the spores kept on popping up as they did. The only remedy was to reduce the excitation by using a thicker excitation filter. Furthermore I added 2 other filters. This combined with higher iso value and longer shutter speed. This setup was used for photo 9.

Photo 10 shows a “garden fern” growing as street decoration. The sori of this one are like crusts that crack open from one end when the sporangi need to be released. As you see, also these were empty, however interesting autofluorescence.

For the last photo (11) I’ve tested my 95x/1,0 (oil immersion) objective with spores. Fortunately the spore in the picture did not move around in the drop of oil. UV excitation and green filter block. It’s the first picture I’ve taken with that objective!