Drought Experiment with Q. buckleyi

9 April 2024

By Ash Waletski and Katelyn Gianni

As the spring semester comes to a close, we have mainly been working on our longest and most detailed experiment so far. Since our last update, we planned and designed an experiment focused on the chronic effects of drought. We chose to work with Quercus buckleyi, the Texas red oak, because it is a close relative to Quercus rubra, the very common Northern red oak that is native to Minnesota (there’s actually a few of these on our campus!). We figured our findings would be more transferable to local ecosystems if we chose an oak species genetically similar to those found nearby.

We want to see if Q. buckleyi saplings that have already acclimated to low water availability, like drought, would have differences in their abilities to uptake water once drought periods are over. We designed our experiment with three groups of five Q. buckleyi saplings each, to control for as many variables as possible (Figure 1). The original states of each group have been maintained for three years in the biology department’s greenhouse, and we changed watering conditions and moved saplings around accordingly about four weeks ago (Figure 2). We had some difficulty moving the saplings that have been grown under well-watered conditions though– they kept getting stuck because of their well-developed roots.

Figure 1. Visual guide for the groups and treatments used.

Every Wednesday since then, we have been looking at the volumetric moisture content left in the saplings’ soil, with the long-term goal of seeing how saplings’ water uptake has been affected. We have been taking and recording percent moisture in each sapling’s soil using a soil moisture sensor (Figure 3). Later this week, we will be diving into another way to see how the saplings have been affected by release from drought– finding specific leaf area, which is the ratio of leaf area to leaf dry mass.

Scientifically, there is a well-documented relationship between a plant’s specific leaf area and the amount of photosynthesis that’s going on inside it; essentially, the denser the leaf, the less photosynthesis it’s able to do. Photosynthesis requires water, so if our experimental group of saplings have different specific leaf areas to either control group, it could be indicative of a change in water uptake. It’s been absolutely fascinating diving into the primary literature behind these processes and learning all about what’s going on inside our little oak saplings. Time and data will tell!

Figure 2. Katelyn rearranging hoses to change watering conditions.

            In the meantime, before we start calculating specific leaf area and between the days that we measure soil moisture, we have been practicing statistical analysis and wrapping up our previous seed germination experiment. Overall, this drought experiment so far has been going quite well and has been a great learning experience. It’s especially been exciting learning new lab techniques. As we mentioned earlier, moving forward our next steps are to calculate specific leaf area, then perform statistical analysis with those values and also with our full soil moisture data. We are very excited to present our future findings to our entire RISEbio team!

Figure 3. Ash measuring soil moisture content using a soil moisture sensor.

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