Effects of Low-Level Aqueous Hydrogen Sulfide and Other Sulfur Species on Lettuce (Lactuca sativa) Seed Germination

Low concentrations of aqueous hydrogen sulfide (H2S) can stimulate growth of some crops. However, it is not clear whether H2S provides crops with only sulfur and whether other sulfur compounds have similar beneficial effects. Therefore, impacts of solutions of sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), sodium sulfide (Na2S), ferrous sulfide (FeS), and H2S at 0.01-1mM were assessed on 5-day lettuce seed germination. Results showed that 0.01mM H2S solution significantly increased lettuce shoot elongation by 40 percent (to 43.6mm from 31.0mm in the control), whereas 0.1mM increased elongation by 24 percent to 38.5mm. Only a slight 10 percent increase was observed in 0.1mM Na2SO4, suggesting that ameliorative impact of H2S on plant growth was not a result of providing sulfur nutrient. Other sulfur solutions, however, inhibited lettuce germination and elongation to varying extents, hinting that H2S might work as a signal molecule in regulating plant cellular activities.