Background
Millions of years of evolution have produced extraordinary adaptations and solutions for plants to face the naturally excessive solar energy which commonly cannot be fully utilized by the light harvesting apparatus of leaves. To find a balance between the harvesting of and the protection against the solar radiation conditions, all plants employ flexible thermal or non-photochemical energy dissipation mechanisms. Yet, inherent capacities for these flexible dissipation mechanisms differ between plant species and can undergo daily and seasonal variations due to the occurrence of physiological strains. The optimized balance between the photochemical and non-photochemical energy pathways of absorbed radiation is a very dynamic concept which remains physically poorly understood. Deriving these energy components and assessing them in a global context would greatly advance our knowledge on the basic energy functioning of vegetation, making room for possible improvements in food production and a better understanding of required capacities and mechanisms plants employ to cope with distinct climatic conditions.
State-of-the-art remote sensing tools to quantify the dynamics of the light reactions
Due to emerging high spectral resolution, remote sensing techniques and ongoing developments to retrieve the spectrally resolved vegetation fluorescence spectrum from several scales, the light reactions of photosynthesis are receiving a boost of attention for the monitoring of the Earth's carbon balance. Sensor-retrieved vegetation fluorescence (from leaf, tower, airborne or satellite scale) originating from the excited antenna chlorophyll a molecule has become a new quantitative biophysical vegetation parameter retrievable from space using global imaging techniques.
Laboratory spectroscopy to unravel the optics of photosynthesis
The methodological basis of the PHOTOFLUX project lies in the design of high-precision spectroscopy protocols for leaf and canopy targets to detect and exploit the dynamic regulation of light harvesting and regulated heat dissipation. Carefully designed laboratory spectroscopy protocols executed under controlled (light, temperature, nutrient, irrigation) conditions in a climate-chamber environment (a LEO group facility) will be performed to measure time series of dynamic features under diverse physiological states.
Reflectance and fluorescence signal processing: from the leaf to the global scale
Although the relationship between solar-induced fluorescence and photosynthesis or gross primary productivity may have been shown as linearly related from global satellite imaging derived from pixels at very large spatial scales, the quantitative link between the fluorescence emission and the actual carbon sequestration currently remains biased due to the many effects. The PHOTOFLUX project focusses on further signal processing of reflectance and fluorescence to establish and refine the link between the optical signals and actual photosynthesis.
