Fig. 2.

SL stability in sample matrices. The relative recovery of GR24 (a) and [²H₆]-5-DS (b), measured after 8 h in contact with sterilized/non-sterilized water, sand wash and sorghum root exudate at 4 °C (blue bars) and 20 °C (yellow bars). Samples were analyzed in three replicates and error bars represent the standard deviation of the mean (± SD). The UHPLC–MS/MS chromatogram shows the comparison of peak areas assigned to endogenous compounds in non-sterilized and sterilized sorghum root exudates, kept at 4 °C (blue line) and 20 °C (black line), respectively