Linking spectral signals with novel photosynthetic parameters from the leaf to the canopy

In recent years, airborne spectroradiometers have become sensitive enough to detect subtle increases and decreases in the depth of oxygen absorption lines caused by fluorescence emission from chlorophylls in plants. This fluorescence emission, termed solar induced fluorescence (SIF), is thought to contain information about photosynthesis, which could be utilised in both precision agriculture and dynamic global vegetation models to potentially help mitigate the threat to food security posed by anthropogenic climate change and a growing human population. This PhD thesis is concerned with understanding the photosynthetic information in SIF at spatial scales ranging from the leaf to the canopy. To do this, a novel technique for remotely measuring photosynthesis, known as Light Induced Fluorescence Transients (LIFT), was coupled with a spectroradiometer, allowing for simultaneous measurements of SIF and photosynthesis. Given the novelty of the LIFT instrument for terrestrial photosynthetic measurements, I first provide a detailed overview of the LIFT instrument calibration and operation, and establish nomenclature for LIFT measurements and data processing. The LIFT instrument was then utilized in three field campaigns supported by laboratory measurements of leaf optical properties and pigments. The aims of these three field campaigns was to: 1) characterise LIFT for use in the field, 2) examine the relationship between photosynthesis and SIF on the leaf-level, and 3) understand the relationship between SIF and photosynthesis at different spatial scales...