| The pollution abatement of soil cadmium (Cd) has become an urgent problem on the global scale. At present, fertilizer and other agronomic measures has improved repair plant growth rate, biomass accumulation and absorption of heavy metals, it has been regarded as one of the most effective means of improve the efficiency of the plant repair (super accumulation of plant). Therefore, the impact of Cd in soil nitrogen by selecting the appropriate form or fertilization methods suitable-transportation and transmission plant systems in the food chain should be deemed as a most important measures of Cd pollution abatement. Indeed, through the pot experiment, this article will studies nitrogen forms (ammonium [(NH4)2SO4], nitrate [NaNO3], nitrate-ammonium [NH4NO3]) based on growth, reactive oxygen and nitrogen metabolism and absorbed the impact of the accumulation of cadmium to provide reference frame for further development and utilization of Cd hyperaccumulator Solanum nigrum, as well as meaningfulness of promoting Cd contaminated soil phytoremediation successful application and popularization.This study shows that different concentrations of Cd stress [0,10,20,40,80,160 mg·kg-1 dry soil] on the growth of S. nigrum seedlings have significantly affected the role.1) The lower concentrations of Cd treatment (≤40mg·kg-1) to promote the growth of seedlings of S. nigrum (leaf traits, root length, plant height and basal diameter) and the accumulation and distribution of biomass; whereas, when the soil Cd stress concentration greater than 40 mg·kg-1 seedlings, and the grown S. nigrum was significantly inhibited.2) Low concentration of Cd stress treatment (10mg·kg-1) leaf chlorophyll a (Chli.a), chlorophyll b (Chl.b) and total chlorophyll (Chl. [a+b]) content; however, with the stress concentration increased levels increase first down trend, and the Chl. A/b ratio changes with increasing stress concentration varies.3) In addition to the stem of phosphorus (P) accumulation of external factors, S. nigrum seedling roots, stems, leaves and fruits of nitrogen (N), P, potassium (K) accumulated volume with increasing concentrations of Cd stress first and then decreased, while higher concentrations of Cd (> 40 mg·kg-1) is gradually reduced.4) With the increasing concentration of Cd stress, root, stem, leaf and fruit Cd accumulation in S. nigrum seedlings gradually increased, and the accumulation of Cd in the order:leaf> stem> root> fruit.5) With the increasing concentration of soil Cd stress, malondialdehyde (MDA) content and catalase (CAT) and superoxide dismutase (SOD) activity increased, but the peroxidase (POD) activity was increased first and then decreased.Exogenous additional different N forms [ammonium [(NH4)2SO4], nitrate [NaN03] and nitrate-ammonium [NH4NO3], it can alleviate the 40 mg·kg-1 soil Cd stress the toxic effects to some extent. 1) The exogenous additional different N forms can significantly improve the aboveground biomass of S. nigrum seedlings and Chl.a, Chl.b and Chl. [a+b] content (in addition to different concentrations of nitrate [NaNO3] for Chl. b no significant effect on the content of outside); and ammonium [(NH4)2SO4] for aboveground biomass yield better than nitrate [NaNO3] or nitrate-ammonium [NH4NO3].2) Compared with 40 mg·kg-1 Cd stress, leaves hydrogen peroxide (H2O2) and MDA levels were significantly lower in the treated under different N forms.3) Cd stress treatment with different concentrations of nitrate [NaNO3] significantly reduced leaf CAT and POD, SOD activity increased first and then decreased. Lower concentrations of nitrate [NaNO3] dealt with under reduced glutathione (GSH) content with the increase of its concentration gradually increased, indicating that GSH plays an important role in regulating resistance to Cd etc.. Meanwhile, CAT activity increased with the additional ammonium [(NH4)2SO4] concentrations, and then decreased; POD activity gradually increased, SOD activity and vice versa. POD with the low nitrate concentrations, ammonium [NH4NO3] add which play a leading role.4) Cd stress significantly reduced seedling nitro reductase (NR) and glutamine synthetase (GS) activity was significantly increased glutamate dehydrogenase (GDH) activity; with nitrate [NaNO3] concentration, NR, GS and GDH activity first and then decreased. With the added ammonium [(NH4)2SO4] concentration increases, NR activity increased gradually to stabilize after the first lift GS activity, and GDH activity decreased to stabilize. With the added nitrate-ammonium [NH4NO3] concentration increased, NR and GS activity increased gradually to a stable, relieve the inhibition caused by Cd stress suffered by GOGAT activity; while GDH activity was no significant difference during treatment.The results of this study show that different forms of S. nigrum N Cd accumulation promote seedling order:[NH4+-N]> [NO3--N]. Therefore, from the point of view of phytoremediation, Cd contaminated soil application of the right amount of ammonium [(NH4)2SO4] can improve Hyperaccumulator S. nigrum biomass accumulation in aboveground and mitigation Cd cadmium stress on reactive oxygen species (ROS) nitrogen metabolism and toxic effects, so it has an important applied value under the environmental engineering practice. |
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