Detecting temperature and water stress in plants with Thermal Infrared Spectroscopy : abstract + powerpoint

Stress in plants generates changes in leaves from decreasing water content to changes in the microstructure and the internal composition of the leave, and changes in the structure of the whole community. Although physiological changes such as water content, relocalization of micro molecules, and macro structural changes such as smaller leaves and canopies are known, the effect of these changes on the thermal properties of plants, and the spectral detection by remote sensors has not been demonstrated yet. This research shows the results of a series of laboratory experiments with an FTIR system (Bruker Vertex70) as a proxy for the remote detection of plant stress in a deciduous
and an evergreen species (European beech Fagus sylvatica and Rhododendron Rhododendron sp.) in the Thermal Infrared (TIR). Four groups of fifteen plants each were separated and treated with cold and warm temperatures (±10°C and 20°C), and poor and well watered conditions. Five leaves of each plant were measured with the FTIR at the beginning and re-measured three months later. These preliminary results show that plants exposed to water and temperature stress have different thermal spectra compared to plants with optimal growing conditions for several sections of the thermal Infrared. Plants under limited water regime showed lower emissivity in regions related to water content (4-6um), but also at longer wavelengths probably associated with adaptations leaf structural traits. Furthermore the evergreen plants (Rhododendron sp.) showed less effect to water stress compared to the deciduous plants (Fagus sp.), suggesting that Rhododendron sp. has more intrinsic resilience to extreme growing conditions.