Today we were working with Amanda (http://www.ucd.ie/plantpalaeo/porter.html), who is researching changes in CO2 levels in the Carboniferous-Permian glaciations. This meant lots of chat about stomata, the tiny pores generally found on the underside of the leaves that are used for gas exchange. She outlined for us how observations made from modern plants can tell us a lot about a similar plant fossil, in terms of the number of stomata present. In general, high concentrations of CO2 lead to low numbers of stomata and in reverse, low levels of CO2 will lead to increased numbers of stomata, as they need to compensate. In the time frames discussed, millions of years ago, we got onto the topic of the dinosaurs and anything else that lived in that time; if levels of CO2 were relatively high, how on earth was anything in the animal kingdom able to survive? What was their secret to living in an atmosphere that we could not thrive in today? I have found it impossible during my time here to completely separate plant biology from all other sciences, once you start into a debate on how living things adapted and survived. More evidence for my students, everything IS connected!
With the theory discussed, we headed for the lab where Amanda showed us a basic method for counting stomata which would be perfect for the classroom with simple resources (clear nail polish and Sellotape).
The clear nail polish was painted in a thin layer over the back of the leaf and left to dry. This layer was then removed with a strip of Sellotape and placed on the slide, then viewed under the microscope. We were shown how to use a computer programme that placed a counting box (for lack of a technical term here on my part!) on sections of the leaf, where we counted the tiny pores. This was really useful for us as teachers as got to make some great slides and images to show in class on the topic.
As wonderful as these were, we went one step up from our usual microscope that we are used to having in school labs and used the fluorescence microscope to produce this image below – highlight of my day!
I am forever changing the image on the desktop on my laptop to something wonderful and pretty like this, and now I can say, I made this image myself! It even strikes me that introducing the topic of stomata to a Leaving Cert group with a picture like this (with me standing just to the left of the screen and giving a class long presentation at how proud I am that I produced this myself!) will surely make it more appealing than merely discussing the small amount of information that they need to know for the course.
Today we also discussed the importance of isotopes when measuring the amount of CO2 in the atmosphere. Plants have a more efficient relationship with carbon-12 (as it is lighter) than carbon-13. This was something that was fairly new to me and of interest from a chemistry point of view – there is much more than identifying leaf shapes and examining fossils needed before we can predict past atmospheres.
With this in mind, we got to crushing some samples of ginkgo leaves to be sent off for isotope analysis in a mass spectrometer.
Today was an enjoyable day in the lab with a very patient Amanda helping us through some of the trickier steps of using a microscope I will unashamedly admit I am very envious of! And did I mention, did you see what I made today!?