Use of the enriched stable isotope S-34 to study sulphur uptake and distribution in wheat

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