Chromium Differentially Affects Hydrogen Peroxide Distribution in Primary and Adventitious Roots of Arabidopsis thaliana L.

The post-embryonic growth of the Arabidopsis thaliana root system can be modified by different types of stress,such as sublethal concentrations of metals,which may induce the production of reactive oxygen species(ROS).In this study,the effects of different concentrations of potassium chromate(K_(2)CrO_(4))on the distribution and relative quantity of hydrogen peroxide(H_(2)O_(2))were determined in primary and adventitious roots in A.thaliana HyPer line seedlings.This line has a biosensor that specifically reports H_(2)O_(2) levels within tissues as fluorescence.Primary root growth was inhibited at 100μM Cr(VI);in contrast,adventitious root formation was induced over the main root growth axis.These structures proliferated from 100-160μM Cr(VI),and much higher concentrations(180-200μM)of K_(2)CrO_(4) were required to affect their growth.The H_(2)O_(2) distributions were observed in the columella and lateral root cap of primary roots of plants grown in medium lacking dichromate,but following the development of toxicity symptoms,H_(2)O_(2) changed its distribution to the meristem and differentiation zones.Conversely,adventitious roots had comparable H_(2)O_(2) distribution patterns in untreated plants and those exposed to Cr(VI)supplementation.Thus,differential H_(2)O_(2) distribution correlates with the resistance of adventitious roots,but not primary roots,to dichromate and underlies cell reorganization at the apex to support growth.

Advances in deciphering salt tolerance mechanism in maize

Maize(Zea mays L.)is a global cereal crop whose demand is projected to double by 2050.Along with worsening of farmland salinization,salt stress has become a major environmental threat to the sustainability of maize production worldwide.Accordingly,there is an urgent need to decipher salt-tolerant mechanisms and facilitate the breeding of salt-tolerant maize.As salt tolerance is a complex trait regulated by multiple genes,and maize germplasm varies widely in salt tolerance,efforts have been devoted to the identification and application of quantitative-trait loci(QTL)for salt tolerance.QTL associated with ion regulation,osmotic tolerance,and other aspects of salt tolerance have been discovered using genomewide association studies(GWAS),linkage mapping,and omics-based approaches.This review highlights recent advances in the molecular-level understanding of salt stress response in maize,in particular in(a)the discovery of salt-tolerance QTL,(b)the mechanisms of salt tolerance,(c)the development of salttolerant maize cultivars,and(d)current challenges and future prospects.

Sunlight-driven reduction of silver ion to silver nanoparticle by organic matter mitigates the acute toxicity of silver to Daphnia magna

Due to the unique antibacterial activities, silver nanoparticles（AgNPs） have been extensively used in commercial products. Anthropogenic activities have released considerable AgNPs as well as highly toxic silver ion（Ag^＋） into the aquatic environment.Our recent study revealed that ubiquitous natural organic matter（NOM） could reduce Ag^＋to Ag NP under natural sunlight. However, the toxic effect of this process is not well understood. In this work, we prepared mixture solution of Ag^＋and AgNPs with varied Ag^＋% through the sunlight-driven reduction of Ag^＋by NOM and investigated the acute toxicity of the solutions on Daphnia magna. Formation of AgNPs was demonstrated and characterized by comprehensive techniques and the fraction of unconverted Ag^＋was determined by ultrafiltration-inductively coupled plasma mass spectrometry determination. The formation of AgNPs enhanced significantly with the increasing of solution p H and cumulative photosynthetically active radiation of sunlight. The toxicity of the resulting solution was further investigated by using freshwater crustacean D. magna as a model and an 8 hr-median lethal concentration（LC50） demonstrated that the reduction of Ag^＋by NOM to AgNPs significantly mitigated the acute toxicity of silver. These results highlight the importance of sunlight and NOM in the fate, transformation and toxicity of Ag^＋and AgNPs,and further indicate that the acute toxicity of AgNPs should be mainly ascribed to the dissolved Ag^＋from AgNPs.

Synthesis of new superabsorbent poly(NIPAAm/AA/N-allylisatin)nanohydrogel for effective removal of As(Ⅴ) and Cd(Ⅱ) toxic metal ions

The present studies highlight the effective removal of As（V） and Cd（II） from aqueous solutions by superabsorbent poly （NIPAAm/AA/N-allylisatin） nanohydrogel. Batch removal studies were performed as a function of treatment time, initial metal ion concentration, pH, and adsorbent dose. TEM micrographs confirm the particle size distribution in the range between 5 nm and 10 rim. The simple and metal ions adsorbed nanohydrogels were characterized by FF-IR, TGA, and EDX analysis. Finally, the equilibrium removal efficiency of the nanohydrogel was analyzed according to the Langmuir and Freundlich adsorption isotherm models which showed the removal of As（V） and Cd（II） metal ions fitted to Freundlich and Langmuir isotherms, respectively. Removal efficiency order of the metal ions is As（V） 〉 Cd（II）.