Are measurements of plant gas exchange accurate?

My project aimed to examine how leaks in the Li-Cor (machine that measures plant gas exchange) chamber affect measurements of photosynthesis. This is important because measurements taken by the Li-Cor are frequently used in models to draw conclusions about how the plant’s biochemistry is working and to make predictions about growth and plant productivity, from the leaf level to the global scale. If the measurements put into the models aren’t accurate, model outputs and any conclusions about what the plant is doing may also be inaccurate. Therefore, my summer project aimed to determine what the leak function looked like graphically, how this leak can be corrected for, and whether having a leak significantly affects model outputs.

To look at this, my supervisor and I took various measurements with the Li-Cor, including with and without plants, and with dead leaf material, to separate structural leaf properties from its biochemical properties. We then plotted the measurements, fitted equations to what we had observed (to be able to quantify the effect of the leak), and then corrected live plant measurements of carbon assimilation. Our results demonstrated that the shape of the leak function is quadratic, with its exact shape differing depending on how the measurements were taken. Results suggested that the nature of the function is due to CO2 absorption in the tubing of the Li-Cor. Our results also indicated that leak correction is important in accurately estimating model parameters, as there was a distinct difference between corrected and uncorrected data estimations.

I really enjoyed the entire summer scholarship experience, but one of the highlights was being mentored by my supervisor. I find that I learn a lot better one-on-one, and there were so many opportunities for this to occur. I got to ask a lot of questions and have aspects of my project, the lab’s work, and important background concepts explained to me. I also loved living on campus and getting to explore Canberra with the other summer students.

First published in the 2017/2018 edition of the Summer Scholars eportfolio.