Effects of Different Sulfur Compounds on the Distribution Characteristics of Subcellular Lead Content in <i>Arabis alpina</i> L. var. <i>parviflora</i> Franch under Lead Stress

Sulfur plays a vital role in the phytoremediation of lead-contaminated soil. The effects of different sulfur forms (S Na₂S, and Na₂SO₄) on lead (Pb) absorption in hyperaccumulator <i>Arabis alpina</i> L. var. <i>parviflora</i> Franch were studied in a soil pot experiment. The subcellular sulfur and lead enrichment characteristics in <i>A. alpina</i> were studied by adding sulfur in different forms and concentrations (0, 75, and 150 mg·kg⁻¹) to Pb-contaminated soil. The results show that the root and shoot biomass increased by 1.94 times under Na₂S and Na₂SO₄ treatment, and the root–shoot ratio of <i>A. alpina</i> increased 1.62 times under the three forms of sulfur treatments, compared with the control. Sulfur content in cell walls and soluble fractions of the root and shoot of <i>A. alpina</i> significantly increased 3.35~5.75 times and decreased 5.85 and 9.28 times in the organelles under 150 mg·kg⁻¹ Na₂SO₄ treatment. Meanwhile, Pb content in the root and shoot cell walls of <i>A. alpina</i> significantly increased by 3.54 and 2.75 times, respectively. Pb content in the shoot soluble fraction increased by 3.46 times, while it significantly reduced by 3.78 times in the shoot organelle. Pb content in the root organelle and soluble fraction decreased by 2.72 and 2.46 times. Different forms and concentrations of sulfur had no regularity in the effect of Pb and sulfur content in the subcellular components of <i>A. alpina</i>, but the bioconcentration and translocation factors of <i>A. alpina</i> increased compared with the control. Under different concentrations of Na₂SO₄, there was a significant positive correlation between the contents of sulfur and Pb in the subcellular components of the root of <i>A. alpina</i> (<i>p</i> < 0.05). These results indicate that sulfur application can enhance the Pb resistance of <i>A. alpina</i> by strengthening the cell wall fixation and vacuolar compartmentalization.