施锰微肥对镉污染土壤中玉米生长及镉吸收分配的影响

为定量研究锰(Mn)对镉(Cd)污染土壤的修复效果,以低(5 mg·kg~(-1))和高(10 mg·kg~(-1))Cd污染棕壤为供试土壤,通过盆栽培养试验,研究施加不同浓度的MnSO4(20、200、2 000 mg·kg~(-1))对土壤Cd形态、玉米生长和体内Cd吸收、Cd亚细胞分布的影响。结果表明:施Mn可以显著改变土壤中Cd的赋存形态,与对照(未施加Mn)相比,土壤可交换态Cd含量降低了4.75%～30.81%,且随着Cd浓度的增加,可交换态Cd降低比例逐渐增大。适量的Mn(20、200 mg·kg~(-1))可以促进玉米根系的生长,提高玉米各部位生物量,增产11.42%～17.51%,但过量的Mn(2 000 mg·kg~(-1))则会对玉米产生一定的毒害作用,导致减产。Mn降低了土壤中Cd的生物有效性,从而抑制玉米对Cd的吸收,籽粒Cd含量在低Cd污染土壤中降低了46.15%～53.85%,在高Cd污染土壤中降低了38.37%～52.33%。同时Mn增加了细胞壁对Cd的沉积和液泡区隔化作用,促进Cd在根部的固持,从而降低其向地上部转运。研究表明,Mn的施加对低Cd污染土壤的钝化效果优于高Cd污染土壤,适量的Mn更有助于玉米的生长发育以及降低玉米体内的Cd含量。

Effects of manganese application on the growth, cadmium uptake and cadmium distribution of maize in cadmium contaminated soil

To quantitatively analyze the remediation effect of manganese(Mn) on cadmium(Cd) contaminated soil, the effects of different concentrations of Mn(20, 200, 2 000 mg·kg^-1) on Cd fractions in the soil, maize growth, Cd uptake by maize, and Cd subcellular distribution were studied by a pot experiment in low(5 mg·kg^-1) and high(10 mg·kg^-1) Cd contaminated brown soil. The results showed that:Mn application significantly changed the Cd fractions in the soil. Compared with the control, the concentration of exchangeable Cd decreased by 4.75%~30.81%, and the decreasing proportion of exchangeable Cd increased with increasing Cd concentration. Moderate Mn (20, 200 mg·kg^-1) promoted the growth of maize roots, enhanced the biomass of all plant parts, and increased the yield by 11.42%~17.51%. However, excessive Mn(2 000 mg·kg^-1) had a toxic effect on maize, resulting in yield reduction. The bioavailability of Cd in the soil was decreased by Mn application, and Cd uptake by maize was also inhibited. The Cd content in the grain in low and high Cd contaminated soil decreased by 46.15%~53.85% and 38.37%~52.33%, respectively. Meanwhile, Mn increased the Cd deposition in the cell wall and vacuolar compartmentation, promoted the fixation of Cd in the root, and reduced the transport of Cd to the shoot. In general, the passivation effect of Mn on low Cd contaminated soil is better than that in the high Cd contaminated soil, and an appropriate Mn application is more conducive to enhancing the growth and development of maize and reducing the Cd uptake.