Regulatory mechanisms of nitrogen (N) on cadmium (Cd) uptake and accumulation in plants: A review.

Cadmium (Cd) is a heavy metal that is toxic to plants and animals. Nitrogen (N), the most significant macro-nutrient and a common input for crop production, is often excessively applied than plants' demands by farmers to obtain more economic benefits. Understanding the regulatory mechanisms of N that control Cd uptake, translocation, and accumulation may enable the development of solutions regarding Cd pollution in the trophic chain, a major and global threat to agricultural sustainability and human health. In this review, we clarified that an increased amount of N, regardless of its form, enhances Cd uptake, translocation, and accumulation in plants, and nitrate promotes Cd uptake more than any other N form. We also described that N fertilizer alters the Cd exchange capacity and the bio-available Cd content in soil; regulates nitric oxide induced divalent cation gene expression of Nramp1, HMA2, and IRT1; and changes cell wall isolation, chelation capacity, and oxidative resistance to regulate Cd accumulation in plants. By revealing the integrated interaction effects between Cd accumulation and N fertiliser use, we propose new challenges to investigate the functions and mechanisms of N in Cd-contaminated croplands and develop suitable N-fertilisation protocols to practically reduce food health risks in agricultural food production.

Dihydrochalcones and Diterpenoids from Pteris ensiformis and Their Bioactivities.

Two new dihydrochalcone enantiomers (+)-1 and (-)-1, along with eight known compounds 3-10, were obtained from Pteris ensiformis. The planar structures were determined on the basis of extensive 1D and 2DNMR and HRESIMS. The resolution of (+)-1 and (-)-1 was achieved by chiral HPLC analysis. The absolute configurations of (+)-1 and (-)-1 were established by the bulkiness rule using Rh2(O2CCF3)4-induced circular dichroism (ICD) method. Compounds (+)-1, (-)-1, 8, 9 and 10 exhibited the inhibitory assay of NO production in mouse macrophages stimulated by LPS, with IC50 values of 2.0, 2.5, 8.0, 9.5 and 5.6 µM, respectively. Otherwise, compound 10 showed moderate cytotoxic activity against HCT-116, HepG-2 and BGC-823 cell lines with IC50 values of 3.0, 10.5 and 6.3 µM, respectively.

Using iron fertilizer to control Cd accumulation in rice plants: a new promising technology.

Effects of two kinds of iron fertilizer, FeSO4 and EDTA.Na2Fe were studied on cadmium accumulation in rice plants with two rice genotypes, Zhongzao 22 and Zhongjiazao 02, with soil culture systems. The results showed that application of iron fertilizers could hardly make adverse effects on plant growth and rice grain yield. Soil application of EDTA.Na2Fe significantly reduced the Cd accumulation in rice roots, shoots and rice grain. Cd concentration in white rice of both rice genotypes in the treatment of soil application of EDTA.Na2Fe was much lower than 0.2 mg/kg, the maximal Cd permission concentration in cereal crop foods in State standard. However, soil application of FeSO4 or foliar application of FeSO4 or EDTA.Na2Fe resulted in the significant increase of Cd accumulation in rice plants including rice grain compared with the control. The results also showed iron fertilizers increased the concentration of iron, copper and manganese element in rice grain and also affected zinc concentration in plants. It may be a new promising way to regulate Cd accumulation in rice grain in rice production through soil application of EDTA.Na2Fe fertilizers to maintain higher content of available iron and ferrous iron in soils.