Understanding how plants interact with their environment is a fundamental goal of plant ecophysiology. As global change progresses, we often draw upon concepts, models and tools in plant ecophysiology to predict how plants will respond to warming temperatures, altered nutrient levels, extreme climate events, drought, novel ecological interactions, and other changing conditions. Many of the concepts and models in plant ecophysiology derive from short term measurements (minutes to hours) at small spatial scales (plant organs or small plants) with low temporal frequency. However, testing hypotheses about physiological mechanisms across hierarchies of space (e.g. in leaves, in whole plants, in canopies and in ecosystems) and time (e.g. phenological responses) remains challenging. For example, in photosynthesis research, measurements of gas exchange, pulse-amplitude modulated fluorescence, leaf traits and chemistry are valuable, but focus on leaves and are difficult to apply at large spatial scales at higher frequency. Eddy covariance observations enable estimations of productivity at the ecosystem scale semi-continuously, but it remains difficult to measure productivity for whole trees and canopies. Multiscale assessments of physiological processes such as photosynthesis would help us understand which processes emerge as important at which scale, and ultimately improve our predictions of how plants will respond to global change. Advances in satellite remote sensing now enable estimations of solar-induced fluorescence—a physical flux linked to the machinery of the light reactions of photosynthesis. Observations of solar-induced fluorescence (SIF) are rapidly becoming available at multiple spatial and temporal scales. For example, SIF in forest canopies can be surveyed with imaging spectroscopy, ecosystems can be monitored with SIF time series across seasons, and SIF for the entire globe can be observed from satellites. Other optical measurements of leaves, such as laser and hyperspectral spectroscopy, have been linked to leaf traits, nutrient levels, canopy structure, leaf chemistry and age. Taking advantage of innovations in both manual and remote sensing technologies to study plant ecophysiology across scales will require conceptual advances including understanding the role of canopy structure and function in re-absorption of SIF, the variation in quenching processes within crowns and canopies, and reflectance of high-spectral wavelength. There are also methodological challenges such best practices in characterizing spectrometers. To bridge scales in ecophysiology with spectroscopy, we need to build bridges between plant ecophysiologists, remote sensing scientists, and those working at their intersection. To this end, this session will bring together scientists with specific expertise ranging from the xanthophyll cycle to canopy structure.