Data for: Direct and indirect effects of floral defoliation on photochemical and non-photochemical chlorophyll fluorescence dynamics of a semiarid bunchgrass

These data were collected in an experimental field study at the USDA-ARS Northern Great Basin Experimental Range, OR, USA, aimed at assessing the effects of floral defoliation on the ability of crested wheatgrass (Agropyron cristatum) florets to dissipate excess light energy over the 2025 plant reproductive period. Basal florets were clipped by 30-50% ca. 3 cm from the distal end of the seed-head, and the chlorophyll fluorescence responses of clipped basal florets and unclipped florets distal to these were compared to those at the same locations on unclipped control seed heads. Chlorophyll fluorescence measurements were made 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 over two days within each of three reproductive phenological periods (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.

本数据集采集自美国俄勒冈州美国农业部农业研究局（USDA-ARS）北大盆地试验牧场开展的田间试验研究，旨在评估2025年植物生殖生长期内，花器官去叶对冰草（Agropyron cristatum）小花耗散过剩光能能力的影响。研究人员在距小穗远端约3厘米处，将基部小花剪去30%~50%的组织，随后对比剪去基部小花及其远端未处理小花的叶绿素荧光（chlorophyll fluorescence）响应，与未做处理的对照小穗相同位置处小花的荧光响应。夜间开展叶绿素荧光测定，以获取暗适应基线荧光（Fo）与最大荧光产量（Fm），并计算光系统II（photosystem II）的最大量子效率（Fv/Fm = (Fm-Fo)/Fm）。次日清晨，当这些小花暴露于自然环境下的全入射光合光子通量密度（photosynthetic photon flux densities）时，再次对同一批小花进行测定，以获取光适应稳态荧光（Fs）、光适应最大荧光产量（Fm'）以及光适应下光系统II的量子效率（PhiPSII = (Fm'-Fs)/Fs）。利用Fs、Fm与Fm'可分别估算光系统II中受生理调控（PhiNPQ = (Fs/Fm')-(Fs/Fm)）与不受调控（PhiNO = Fs/Fm）的非光化学能量损失（non-photochemical energy loss）量子产额。数据采集于三个生殖物候期（开花前期、开花期、开花后期）内的每个时期的两个日间，同步通过每日6次10厘米土层体积含水量（Vsm）观测获取日均该土层体积含水量。