Fluorescence Imaging as a Non-Invasive Technology to Monitor the Performance of Glyphosate Adjuvants and Formulations

Fluorescence can be used to measure and visualize the activity of herbicides that inhibit the photosynthesis. Glyphosate, although not acting primarily on the photosystems, appears to increase fluorescence of plants. We investigated whether fluorescence technology is a useful tool to both quantify and image of the performance of different adjuvants for glyphosate. A red laser beam providing equipment is used to scan black nightshade plants at a low and high light intensity. A cooled, integrating 16 bit CCD camera is used to record the fluorescence during the low level (Fo) and high level scan (Fm). The relative increase of fluorescence expressed as [(Fm¿Fo)/Fm] 100 % is calculated and color images are produced. Glyphosate was applied at two suboptimal application rates of 16.9 and 33.8 g ae/ha at 200 L/ha. Both the influence of glyphosate rate and the influence of added adjuvants were obvious. The fluorescence data 30 h after treatment demonstrated that the adjuvants HM9121-A and HM9110 performed better than AMS, HM9541-A, HM9910, or HM2005-B. This observation was consistent over the next three observations (54, 78, and 102 h). The fluorescence data after 72 h correlated (R2=0.82; logarithmic regression) with the fresh weight reduction caused by the glyphosate treatments. The adjuvants HM 9121-A and HM9110 performed the best and the adjuvant HM9541-A had little effect on glyphosate performance. Both imaging and fresh weight data indicate that HM 9121-A performs somewhat better than HM911