National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China.
National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China.
Ecotoxicol Environ Saf. 2020 Sep 1;200:110746. doi: 10.1016/j.ecoenv.2020.110746. Epub 2020 May 22.
Cadmium (Cd) pollution is a worldwide concern due to its biotoxicity. Because Cd and Fe are closely associated during plant photosynthesis, this study aims at investigating the mechanism governing Cd toxicity during photosynthetic primary reaction in rice by adjusting Fe concentration. The results show that moderate Fe concentration (1.0 g kg) added to soil can increase the stomatal conductance (Gs) and SPAD value by stimulating the stomatal opening and chlorophyll synthesis. Moderate Fe concentration can also improve the maximum fluorescence (Fm) and the maximal photochemical efficiency (Fv/Fm) to keep the high reaction center activity and electronic transfer efficiency in photosystems I and II. Thus, moderate Fe can eliminate Cd-induced decrease in Gs, intercellular CO concentration (Ci) and net photosynthetic rate (Pn) as well as the disorder of antioxidative system under Cd concentration of 2.0 mg kg in the soil. When its application is increased to 2.0 g kg, Fe can notably decrease Pn, and result in remarkable decrease in the biomass of shoots and grains. Decrease in Pn can be mainly attributed to high Fe concentration which can greatly destroy chloroplast structure and, meanwhile, inhibit the electron transfer between acceptor and donator in photosynthetic chain especially from quinone A (Q) to quinone B (Q). Unlike the situation under moderate Fe concentration, the high Fe application cannot mitigate the Cd-induced decrease in photosynthetic index. Our results indicate that the moderate Fe application is necessary to promote rice performance and production and, in the meantime, to inhibit Cd toxicity in the extensively polluted soils.
镉（Cd）污染是一个全球性的问题，因为它具有生物毒性。由于 Cd 和 Fe 在植物光合作用过程中密切相关，因此本研究旨在通过调节 Fe 浓度来研究光合作用原初反应过程中 Cd 毒性的调控机制。结果表明，适量的 Fe 浓度（1.0 g kg）添加到土壤中，可以通过刺激气孔开放和叶绿素合成来增加气孔导度（Gs）和 SPAD 值。适量的 Fe 浓度还可以提高最大荧光（Fm）和最大光化学效率（Fv/Fm），以保持光系统 I 和 II 中的高反应中心活性和电子传递效率。因此，适量的 Fe 可以消除 Cd 引起的气孔导度（Gs）、胞间 CO2 浓度（Ci）和净光合速率（Pn）下降，以及土壤中 2.0 mg kg Cd 浓度下抗氧化系统的紊乱。当应用量增加到 2.0 g kg 时，Fe 可以显著降低 Pn，导致地上部和籽粒生物量显著减少。Pn 的降低主要归因于高 Fe 浓度，它会极大地破坏叶绿体结构，同时抑制光合作用链中电子从受体到供体的传递，特别是从醌 A（Q）到醌 B（Q）。与适量 Fe 浓度下的情况不同，高 Fe 应用不能减轻 Cd 引起的光合指标下降。我们的结果表明，适量的 Fe 应用对于促进水稻的性能和产量是必要的，同时也可以抑制受污染土壤中 Cd 的毒性。
