Fluorescence imaging for rapid monitoring of translocation behaviour of systemic markers in snap beans for automated crop/weed discrimination

Investigating the translocation behaviour of fluorescent markers is significant for the effective application of the markers in weed and crop differentiation. Snap bean was used as a model plant to study the systemic movement of Rhodamine B (Rh-B) in specialty crops for weed control. A fluorescence imaging system was developed to monitor the uptake and translocation of Rh-B from dyed snap bean seeds to bean plants. Bean samples were dyed using different concentrations of Rh-B solutions. As the concentration of Rh-B applied to the seeds increased, the fluorescent signal of the marker was at first enhanced, then weakened. After germination, this marker was observed from the stems of bean seedlings at stages of first leaf to multiple leaves over time. The fluorescence response on the hypocotyl was stronger than that on the epicotyl, while there was limited translocation observed in plant roots and leaves based on this fluorescence imaging system. The fluorescence peak at 590 nm, measured by a spectrometer (350-1050 nm), exhibited the greatest contrast between untreated and treated plant samples. The proposed crop signalling approach based on Rh-B emission was able to classify snap bean plants from different weeds (e.g. burning nettle, groundsel, and barley). The results demonstrate that fluorescence imaging technology is a rapid and effective approach to studying the real-time translocation behaviour of a signalling marker in a crop system. Based on the unique fluorescence property, visualisation of the marker in vivo specialty crops grown from Rh-B treated seeds provides potential for their successful application in early season weed discrimination. (C) 2019 IAgrE. Published by Elsevier Ltd. All rights reserved.