Examining the Ability of Remote Sensing to Characterize Turfgrass Stress Physiology

Remote sensing of solar induced chlorophyll fluorescence (SIF) is a valuable tool in understanding the global carbon cycle. While SIF is highly correlated with photosynthesis at the ecosystem scale, the role that remote sensing of SIF can play at smaller scales is still unclear. The goal of my research was to investigate the ability of SIF to detect changes in pigmentation, photosynthesis, and energy partitioning at the grass canopy and leaf level in response to water stress and abscisic acid (ABA) hormone treatments. Both treatments immediately inhibited photosynthesis by limiting gas exchange through stomatal closure, but SIF declined gradually. Recovery of photosynthesis after alleviation of water stress was not reflected in remote measurements of SIF. I found that senescence in the tips of grasses had been driving changes in remote measurements, which affected remote measurements even when measured leaf-level gas exchange in the lower living tissue recovered. This heterogeneous senescence pattern contextualizes the disconnect between SIF and photosynthesis in stressed turfgrass.