USE OF THE ENRICHED STABLE ISOTOPE³⁴S TO STUDY SULPHUR UPTAKE AND DISTRIBUTION IN WHEAT

Elemental sulfur (S) highly enriched in the stable isotope 34S (90 atom %) was converted quantitatively to sulfate and used as a tracer to investigate S uptake and distribution in wheat (Triticum aestivum L. cv. Axona). The 34S label was fed to wheat for 24 h at different growth stages in hydroponic culture. The 34S abundance in plant samples was determined using a continuous flow elemental analyzer coupled with an isotope ratio mass spectrometer. The unlabeled plant tissues showed very similar S isotope composition to the S source used in the nutrient solution, whereas labeled plants contained 0.43–18.88 atom % excess 34S over the background. Total amounts of the 34S label in the whole plants did not differ significantly between those harvested immediately after the labeling period and those harvested at anthesis. Stems and roots were the main contributors of the 34S label to ears up to the anthesis stage. This study shows that highly enriched 34S can be reliably used in plant nutrition studies.