Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Str. 2, 24118, Kiel, Germany.
College of Life Sciences, Yan'an University, Yan'an, 716000, Shaanxi, China.
Environ Sci Pollut Res Int. 2018 Nov;25(33):33794-33805. doi: 10.1007/s11356-018-3266-6. Epub 2018 Oct 2.
Sulfur deficiency and cadmium (Cd) pollution are two ubiquitous constraints affecting plant growth in agricultural soils. However, facing the situation of sulfur deficiency, whether surplus sulfate supply can affect Cd toxicity in plants is still unclear. Therefore, in the present study, experiments with deficient, sufficient, and excess sulfate levels under Cd stress were conducted in faba bean plants hydroponically. We found that sulfate supply significantly increased biomass of Cd-stressed plants when compared with deficient sulfate treatment. Intriguingly, sulfate application also increased Cd concentrations in leaves. Based on increased Cd concentrations without retarding plant growth, we conclude that sulfate supply enhances Cd tolerance in faba bean plants. Sulfate application increased CdSO proportion in the growth medium which is partially related to the increase of Cd in plants because the diffusion of CdSO is faster than Cd in plants. Further study on Cd localization showed that this heavy metal was prone to accumulate in the epidermis of leaves as affected by sulfate which might contribute to enhancement of Cd tolerance. Oxidative stress induced by Cd toxicity was alleviated by surplus sulfate supply compared with deficient sulfate. Although capacities of total antioxidants were increased by sulfate in Cd-stressed plants, phenolic compounds as one kind of important antioxidants were unchanged, suggesting that sulfate has no effect on phenolic compounds for scavenging ROS under Cd stress. Taken together, sulfate accelerates Cd accumulation in the epidermis of leaves in faba bean giving rise to higher Cd tolerance.
硫缺乏和镉（Cd）污染是影响农业土壤中植物生长的两个普遍存在的限制因素。然而，在面临硫缺乏的情况下，过量的硫酸盐供应是否会影响植物的 Cd 毒性尚不清楚。因此，本研究在水培条件下对蚕豆植物进行了缺硫、充足和过量硫酸盐水平下的 Cd 胁迫实验。我们发现，与缺硫处理相比，硫酸盐供应显著增加了 Cd 胁迫下植物的生物量。有趣的是，硫酸盐的应用也增加了叶片中的 Cd 浓度。基于在不减缓植物生长的情况下增加 Cd 浓度，我们得出结论，硫酸盐供应增强了蚕豆植物对 Cd 的耐受性。硫酸盐的应用增加了生长介质中 CdSO 的比例，这与植物中 Cd 的增加部分相关，因为 CdSO 的扩散速度快于植物中的 Cd。进一步对 Cd 定位的研究表明，这种重金属容易在叶片表皮中积累，这受到硫酸盐的影响，这可能有助于增强 Cd 耐受性。与缺硫相比，过量的硫酸盐供应缓解了 Cd 毒性引起的氧化应激。尽管硫酸盐在 Cd 胁迫下增加了植物的总抗氧化能力，但酚类化合物作为一种重要的抗氧化剂没有变化，这表明硫酸盐对酚类化合物在 Cd 胁迫下清除 ROS 没有影响。综上所述，硫酸盐加速了 Cd 在蚕豆叶片表皮中的积累，从而提高了 Cd 的耐受性。
