Data from: Photochemical and non-photochemical chlorophyll fluorescence dynamics in reproductive structures of semi-arid rangeland perennial bunchgrasses

These data were collected in a field study at the USDA-ARS Northern Great Basin Experimental Range, Oregon, USA, aimed at assessing the photochemical efficiency and ability of florets and flag leaves of two important sagebrush steppe bunchgrasses -- Crested wheatgrass (<i>Agropyron cristatum</i>), and Bluebunch wheatgrass (<i>Pseudoroegneria spicata</i>) -- to dissipate excess light energy over the 2025 plant reproductive period. Chlorophyll fluorescence measurements were made on flag leaves and distal and basal florets at night to determine dark-adapted baseline (Fo) and maximum fluorescence yields (Fm) and to calculate maximum photosystem II quantum efficiency (Fv/Fm = (Fm-Fo)/Fm). The same florets were then measured again the following morning when exposed to full incident ambient photosynthetic photon flux densities to determine light-adapted steady state fluorescence (Fs), maximum fluorescence yields (Fm') and light-adapted photosystem II quantum efficiency (PhiPSII = (Fm'-Fs)/Fs). Fs, Fm and Fm’ were used to estimate the quantum yield of non-photochemical energy loss (NPQ) in PS II that is physiologically regulated (PhiNPQ = (Fs/Fm’)-(Fs/Fm)) and unregulated (PhiNO = Fs/Fm). Data was collected five times over the entire reproductive cycle (pre-anthesis, anthesis, and post-anthesis), with concurrent average daily volumetric soil moisture at 10 cm soil depth (Vsm) from six Vsm observations made daily.