Abstract
The objective of this research was to experimentally determine whether signs of water deficit stress in plants can be detected from changes in the absorbance spectra based on the relationships between absorbance spectra and physiological parameters. Absorbance of tomato leaves in the near-infrared (NIR) wavelengths (1100 nm to 2500 nm) was measured simultaneously with photosynthesis and stomatal conductance during water stress. To observe small changes in absorbance which arise from water stress, a leaf in non-stressed conditions was used as a reference for the absorbance measurements. In general, under the effects of water stress, peaks formed in the absorbance spectra at water absorbance bands near 1 440 nm and 1 940 nm, and absorbance decreased near 1 600 nm forming a valley. Although the relationship between the changes in absorbance and physiological parameters varied depending on the individual plants tested, consistent overall trends were observed, demonstrating there is potential to nondestructively detect changes in plant condition resulting from water stress by measuring NIR absorbance.
