Sporangia and autofluorescence

by Walter Machielsen

February 6, 2024

 WSporangia 1 alter Machielsen ©

Sporangia 1

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 all through 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.

Sporangia 2  Walter Machielsen ©

Sporangia 2

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.

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 as previously mentioned, radiation colour more purple and blue. Excitation for all was ultraviolet.

Sporangia 3 Walter Machielsen ©

Sporangia 3

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.

 Sporangia 4 Walter Machielsen ©

Sporangia 4

 WSporangia 5 Walter Machielsen ©

Sporangia 5

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. This was better than the 21x objective, see below picture

 Sporangia 6  Walter Machielsen ©

Sporangia 6

Sporangia 7

Sporangia 7

 Sporangia 8 Walter Machielsen ©

Sporangia 8


Sporangia 9   Walter Machielsen ©

Sporangia 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!

Sporangia 10  Walter Machielsen ©

Sporangia 10

 WSporangia 11 alter Machielsen ©

Sporangia 11



Authors Biography & Contact Information

Portrait of Walter Machielsen

Walter Machielsen is a photographer from Rotterdam in the Netherlands. Microscopy has many different aspects, including a connection with nature photography.





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Email at: walterdmachielsen@gmail.com
Web site: www.waltermachielsen.nl