No post last week because my wife Laura and I had spent the week before in Rome. I considered blogging about our sightseeing, we did visit the Botanical Gardens—well worth a tourist’s digression, but I felt that travel-gazing is not quite the spirit of Lab Fab. Also, I was flat-out tired: visiting Rome features kilometers and kilometers of walking around. 

Back in the lab this this past week, I encountered a mysterious reticulum (Fig. 1). The image is taken through a microscope with phase-contrast optics and 10-x magnification. Sorry, there is no scale bar; I estimate the width of the image to be about half a millimeter so the strands are ~10 to 30 µm wide. Also sorry that I did not focus properly, taking a picture was an afterthought, I didn’t have my spectacles, and I was in a hurry. Still the reticulum is unmistakable. 

I found this anastomosing network on the surface of the agar medium on which I grow plants. Before I left for Rome, I had dutifully plated seeds, put the plates in the fridge, and asked a colleague, the indefatigable Andrew Plackett, to move them into the growth chamber (or cabinet in the local lingo) while I was away so I would have plants upon my return. Two things were pressing: First, having been evicted from good old Cabinet C, the unit I had determined way back last autumn to give good growth, I needed to check results in the new cabinet (E). Second, I am getting close to being able to try things on the multiphoton microscope and I wanted to have plants for that, just in case. I had two plates for testing root growth rate, prepared so that the roots would grow on the agar surface; I had two other plates in preparation for the fancy pants microscope, prepared with roots growing inside agar, the latter supplemented with the cellulose stain, Calcofluor white. 

Returning home, I discovered a third thing: While I was away, the University was subjected to plug testing. Every plug in every room, both laboratory and office, must be inspected and proved to be sound. The office I am sharing with a professor who lives in Dorset (sic) and comes in rarely has obsolete computer gear piled up in dusty stacks: all of it was hauled out and tested. In the lab, they shoved aside the microscope and external IR light source that I have set up for imaging root growth. This meant, it needed to be realigned. I am trying hard to restrain myself from venting about this University-wide exercise in futility—and failing!

OK, fine. On Friday, when it was evident, sigh, that there was to be no testing of the multiphoton, I used the plates with roots inside the agar to realign the microscope. Those are the kind I will be imaging anyway on that ‘scope. Happily, things popped back into alignment without much fuss. But there, sort of shadowing the roots, was some vague texture. Difficult to discern but it moved with the plate so it was not part of the optics. I took the plate to a nearby microscope that has phase-contrast optics, good for imaging transparent, weakly scattering structures. And hey presto! the mysterious reticulum (Fig. 1). 

Both plates were so embellished. As far as I could tell, looking here and there across the surface of these large (10 cm x 10 cm) plates, the reticulum appeared similar. I added some water to the surface and a coverslip but the reticulum appeared unaffected. There were neither foci of origin nor regions of diminution. This makes me think the phenomenon is physical, not biological. I wondered whether to blame the process I used to add Calcofluor to the plates. 

Yesterday (yes, Saturday) I went into the lab to finish the experiment for testing the growth rate in the cabinet; I had wanted to let them grow for one more day. This used the pates with plants growing on top of the agar. I checked the surface: The mysterious reticulum was present in all its glory. This rules out the Calcofluor. Also, these plates and those with the Calcofluor were made at different times and with different batches of medium, making unlikely some piece of weirdness while mixing up the ingredients. 

So what is this stuff? My favorite (well, only!) explanation is that, in manufacture of the plates, some kind of coating remained on the surface. When I add the hot agar, the leftover film could have risen to the surface and broken up into a reticulum, driven by its surface tension along with some kind of interfacial jiggery pokery. Can this dog hunt? or even walk? I have no idea. But I need to get rid of this reticulum because it will interfere with imaging and I think that the roots are growing too slowly, tho that could just be down to Cabinet E.