Investigating the Impacts of Drought on Turfgrass (Festuca arundinacea) Chlorophyll-a Fluorescence Emission

When photons from sunlight are absorbed by plants, they can take paths of photosynthesis, fluorescence, or energy dissipation. Instruments to quantify fluorescence have expanded in scale to allow measurements from satellites and flux towers using Solar-Induced Chlorophyll Fluorescence (SIF). Studies have found a positive correlation between SIF and gross primary productivity (GPP; representative of photosynthesis), suggesting SIF is a proxy for GPP. This conclusion encourages the use of SIF to inform decisions about carbon budgets and responding to climate change. Studies of fluorescence on the single-leaf scale have revealed that SIF measurements do not account for all variables nor is there an understanding of the impact of environmental factors, such as drought, on these measurements. In this project, tall fescue turfgrass was placed in one of four differing drought severities for 19 days. Leaf-level measurements of photosynthesis and pulse-amplitude modulated fluorescence were made, demonstrating stomatal closure and inhibition of photosynthesis. This physiological change caused greater photon allocation to energy dissipation. Changes in greenness and the utilization of photoprotective mechanisms such as senescence and anthocyanin accumulation were observed. This study has provided an understanding of the temporal, physiological, and visible impacts of drought on turfgrass to inform interpretations of SIF in future experiments. Caution is crucial in utilizing SIF as a proxy for GPP before further research into the impact of drought on SIF is completed.