Grassland species are more efficient in acquisition of S from the atmosphere when pedospheric S availability decreases

Abstract

Plants can absorb Sulfur (S) either through roots as sulfate or via leaves in a gas form such as SO2 or H2S. This study aims to examine whether the most efficient competitors for root uptake of sulfate among grassland species are also those with the greatest ability for foliar uptake and to test whether all species can increase their ability to use atmospheric S when available sulfate decreases. Six grassland species were grown together in a non-S-enriched-atmosphere for 60 days with two levels of sulfate concentrations. Sulfate was 34S-enriched to distinguish root uptake of sulfate and foliar uptake of gaseous S. Grasses were more competitive for sulfate uptake and more efficient at producing biomass for the same amount of S in comparison to the non-fixing forb and the legumes. All species studied were able to increase their ability to use atmospheric sources of S when sulfate availability decreased. The percentage of S derived from the atmosphere was strongly related to sulfate concentration in leaves. Grasses were more efficient for root sulfate uptake but forbs seemed more efficient for foliar uptake. Sulfate in plant tissues could play a key role in regulation between the foliar and root S uptake.