Sulfur starvation reduces phytosiderophores release by iron-deficient barley plants

The aim of the present study was to examine the effect of sulfur (S) Supply on the response to iron (Fe) deficiency in graminaceous plants. Barley seedlings (Hordeuni vulgare L. cv. Europa) were cultured hydroponically for 10 days at three S levels (0, 60 and 1200 mu mol L-1 sulfate) with (+Fe) or without (-Fe) 100 mu mol L-1 Fe-III-ethylene diamine tetracetic acid. Lowering S supply resulted in a sharp decrease in the release of phytosiderophores by Fe-deficient barley plants. Furthermore, uptake of Fe-59 from (Fe-59)-hydroxide decreased by approximately 30% when S availability was lowered; Fe deficiency caused a sharp increase in Fe-59 uptake that was as high as the level of S supply. The results support the view that S availability can influence either the release of phytosiderophores or the ability to take up Fe from an external solution.