Thermal imaging of soybean response to drought stress: the effect of Ascophyllum nodosum seaweed extract

Previous experiments have demonstrated positive effect of Acadian (R) extract of Ascophyllum nodosum on plant stress-resistance, however the mode of action is not fully understood. The aim of this study was to understand the physiological effect of Acadian (R) seaweed extract on the plant response to drought stress. Leaf temperature and leaf angle were measured as early-stage indicators of plant stress with thermal imaging "in situ" over a 5-day stress-recovery trial. The early stress-response of control became visible on the third day as a rapid wilting of leaves, accompanied with the asymptotic increase of leaf temperature on 4-5 degrees C to the thermal equilibrium with ambient air temperature. At the same time Acadian (R) treated plants still maintained turgor, accompanied with the linear increase in leaf temperature, which indicated better control of stomatal closure. Re-watering on the fifth day showed better survival of treated plants compared to control. This study demonstrated the ability of Acadian (R) seaweed extract to improve resistance of soybean plants to water stress.