Competition for S-containing amino acids between rhizosphere microorganisms and plant roots: the role of cysteine in plant S acquisition

Abstract Plant S deficiency is common, but the role of S-containing amino acids such as cysteine in plant uptake unknown. We applied 14 C-, 35 S-, 13 and 15 N-labelled to wheat oilseed rape rhizospheres traced plants’ elemental uptake. Both plants absorbed 0.37–0.81% intact after 6 h with no further increase 24 h. They 1.6–11.5% 12.3–7.6% N from utilised SO 4 2? their main source (75.5–86.4%). Added naturally occurring cysteine-S contributed 5.6 1.1% total by rape, respectively. Cysteine inorganic derived 24.5 13.6% for respectively, Oilseed ~10-fold more than did wheat. The highest absorption free should be organic-rich soil patches. Soil microorganisms rapidly decomposed (t 1/2 = 1.37 h), roots mineralised S. After min, 11.7–14.3% S-cysteine was retained microbial biomass, while 30.2–36.7% released, suggesting that rapid immobilisation occurs addition. Plants acquire via unidirectional soil-to-root nutrient flow, an important plants.