Remote Sensing acquires optical data across space and time. We then want to interpret the data in terms of spatial and temporal variation in plant functional or biochemical traits. In a recent paper (Atherton et al. 2017, see publications) we investigated the background spatial variation in key optical properties/traits like the photochemical reflectance index or the shape and intensity of the leaf chlorophyll fluorescence spectra and  the factors that control it. We found that both the light environment within plant canopies and the species generate background spatial variability in the above optical traits which needs consideration when interpreting remotely sensed data.