By: Ashley Waletski and Katelyn Gianni
We have just started our second-semester RISEbio project! We are still observing the impacts of drought stress on Quercus (oak) saplings, but this time, using some new metrics, and a different species, Q. agrifolia. We learned an exciting new lab technique to use in our experiment – finding proline concentrations in leaves. Proline is an osmolyte produced by plants when they are under stress (like drought, which we are studying). Proline in freeze-dried and pulverized leaf tissue reacts to ninhydrin, a chemical we add, forming a red hue; the deeper red, the more proline present. This red color can be quantified using spectrophotometry, after which we can plot points on a graph in relation to known proline values, to figure out exactly how much proline was in that leaf. Here (in Fig. 1) you can see test tubes of leaves we sampled, in a container of liquid nitrogen, being prepared to be freeze-dried. We haven’t quantified proline quite yet for the experiment with our own Q. agrifolia specimens, but we spent time last week preparing leaves to do so (Fig 2).
Another new metric we learned and examined between our mesic and xeric groups this week was leaf dry matter content (LDMC), which is a measure of how much of a leaf’s mass is water weight, and how much the actual leaf tissue. LDMC is calculated as the ratio between the mass of a freshly picked leaf and the mass of that same leaf when dry. To find this, we plucked one leaf per sapling, weighed and recorded each leaf’s mass, dried the leaves out in a drying oven, then weighed them again to find that dry mass. Additionally, separate from LDMC but using this same data, we found how much weight in the fresh leaves was due to water content. Fascinatingly, this averaged 39.9% for mesic and 40.5% for xeric (that’s a lot of water!).
Also during this past week, we submitted proposals for institutional undergraduate research grants – this semester, in addition to and inspired by our RISEBio work together, the two of us decided to start separate independent study projects. These individual research projects will build our research skills even more, especially through reading lots of primary literature, which will strengthen the work we do in RISEbio too.
It’s been a great start to the semester with lots of new experiences for us! Whether it be designing this experiment, learning lab skills like proline quantification, learning more functional traits like LDMC, or exploring even more research, everything has been so exciting.
