Be Leaf in Yourself

March 26, 2024

By Harper Gillespie & Kayleigh Cottrell

The past month has been consumed with experiments and observations. To start, we planted the seeds that had been germinating into a tray in the greenhouse. We have also begun our own experiment that we recently proposed. Last week, we also conducted a seed viability test to determine if the provided seeds are viable to grow.

Figure 1. Harper adding soil into cells to plant our seeds into.

At the beginning of the semester, we had the opportunity to use seeds and their germination codes to understand their growth. Foxglove beardtongue (Penstemon digitalis) and switchgrass (Panicum virgatum) seeds were chosen and 25 of each were placed into a coffee filter and a Ziploc bag. We used four Ziploc bags, two of which were foxglove and two were switchgrass. From each species, we chose one bag to add mycorrhizal inoculant and water to see if it impacted growth or germination. We hypothesized that the mycorrhizal inoculant would increase the growth of the seeds due to the properties it holds. Mycorrhizal inoculant is used to help the return of mycorrhizal fungi and works well on nutrient-poor soils. After adding water to both, they were placed into the fridge for approximately six weeks. A few weeks ago, the seeds were removed from the fridge and added to the window in a greenhouse bay to enhance their growth. After just a week we noticed sprouts coming from both species. We then added potting soil to a tray of cells and placed the sprouts into them. After continuously doing the process of identifying sprouts and then planting them we only have a few seeds that have not sprouted. We water the seeds and observe their growth twice a week. Presently, the switchgrass has grown the fastest and the tallest, likely due to its germination code (it needs no extra help to grow). The foxglove has been increasingly growing successfully.

Figure 2. Kayleigh observing stomata openings within one of the oak species.

We have also had the opportunity to create our experiment to do for the rest of the semester. We decided to research oak species to determine if they have a memory of prior drought stress. To do so, four oak species were chosen that were from wet (hydric) and dry (xeric) environments. Q. laevis and Q. virginiana have a native range in wet environments while Q. ellipsoidalis and Q. lobata are from dry environments. We will take the oaks out of drought and water them every day instead of every three days. The stomata within each species will be observed. Stomata are microscopic openings found in leaves that are responsible for gas and water exchange and can be closed or opened depending on their environments (Fig. 2). As a result, stomatal peels will be taken before and after the watering treatment is changed. Stomatal peels are taken to observe the stomata in living plants by putting nail polish on a section underneath the leaf and peeling it off. The peels are then put under a microscope for observation. Five stomatal widths on each peel will be averaged from each species. We hypothesize that the oak species will remember prior drought stress. If they remember the prior drought stress, then the stomata of the well-watered oaks will remain closed to hold in their water. The collected stomatal data will be added to a Microsoft Excel sheet. We will then compare and analyze the data to reject or accept our hypothesis.

For the viability experiment, we were provided with cup plant (Silphium perfoliatum) seeds. To test the viability of seeds, we did a Tetrazolium Test (or TZ test). We began by shaving the outer coating off the seed with a razor blade to reveal the inside portion of the seed that we tested. After, the cut seeds were placed in a petri dish on filter paper, and we poured TZ solution over the seeds, so the filter paper was fully saturated. Our petri dish specifically was placed in the fridge because our lab is days apart, to slow the reaction time. The TZ solution will stain the live tissues red, and the dead tissues will have no color change. We will find out soon if the cup plant seeds are still viable.

The growth of foxglove and switchgrass is fascinating to observe. We wonder if the mycorrhizal treatment will show a difference within the next few weeks. In addition, we are excited to begin our experiment and observe the impacts of going from drought to well-watered on stomata.

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