Simultaneous efflux and uptake of metabolites by roots of wheat

Some metabolites (e.g. amino acids) present in root exudates can be taken up by roots, but we do not know if this ability extends to the broader suite of metabolites found in exudates. The aim of this study was to examine the ability of wheat (Triticum aestivum L.) to efflux and take up a broad suite of small metabolites. Four-week-old plants were placed into an uptake solution that contained a broad suite of C-13-labelled metabolites. Uptake was estimated from the decrease in concentration of the C-13 isotopologue in the solution; and from the appearance of C-13 isotopologues within roots. Efflux was estimated from appearance of C-12 isotopologues in solution. When wheat plants were placed in C-13-metabolite solutions the concentration of U-C-13 isotopologues of 37 metabolites decreased - as would be expected if plants were taking up the U-C-13 metabolites. After 4 h immersion in C-13 metabolite solution, roots contained detectable amounts of U-C-13 isotopologues of 55 metabolites. U-C-13 isotopologues of organic acids were not detected within roots. These findings indicate that wheat can take up a broad suite of N-containing metabolites and some sugars, but there was no evidence for uptake of organic acids.