Spectral reflectance of Lemna gibba fronds exposed to ethylene glycol

Spectroradiometry was used to quantify changes in duckweed frond reflectance that occurred throughout the 400–850 nm spectrum under various ethylene glycol (EG) concentrations and exposure times. The threshold concentration of EG at which a reflectance change could be detected was between 35 and 40 mM ( P≤0.01), approximately, the same as by visual observation. EG-induced changes in frond reflectance were maximal at concentrations of 50 mM or greater. Reflectance changes were detectable within 24 h of exposure to 100 mM EG, 2–3 days prior to changes in frond appearance. Thus, spectroradiometry of duckweed may serve as a rapid and sensitive technique for detection of ecosystem exposure to EG and perhaps other stress agents.