Stress Effects on Leaf and Canopy Reflectance and Crop Productivity.

Plant responses to water stress include various photoprotective mechanisms, which modify CO2 uptake, net energy exchange and gross primary productivity (GPP). Field studies, conducted over 13 years, on irrigated continuous corn, irrigated corn/soybean rotation, and rainfed corn/soybean rotation (at the Mead, NE Ameriflux sites) have revealed relationships between integrated GPP and grain yield.  Changes in canopy reflectance due to the invocation of photoprotective mechanisms provide an opportunity to relate stress conditions to the resulting carbon fluxes. Recent field work also highlights the influence of photoprotective mechanisms on commonly-used remote sensing indices  used to estimate canopy biophysical parameters.