Phytolacca acinosa Roxb. with Arthrobacter echigonensis MN1405 enhances heavy metal phytoremediation

Constructed wetlands and hyperaccumulators for the removal of heavy metal and metalloids: A review

Water pollutions of heavy metal and metalloids (HMMs), typically including As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn, are becoming a severe environmental problem to be controlled. Constructed wetlands (CWs) have been intensively investigated and applied for the removal of HMMs. By analyzing a mass of data from the existing literatures, this review found that the HMM removals in CWs varied from 12.35 % to 91.01 %, depending upon the HMM species and CW conditions. Nonetheless, 88.50 % of the influent HMMs were eventually immobilized in the CW sediments, while the common wetland plants are inefficient (i.e., accounting for 4.64 %) to uptake and accumulate the HMMs. It was also found that the concentrations of certain HMMs in the CW sediments have already exceeded up to 100 % of various environmental standards, indicating the urgency of introducing HMM hyperaccumulators in the systems. Through comparison, both the aboveground and belowground HMM accumulating capacities of reported hyperaccumulators were higher by magnitudes than common wetland plants. Following this, the efficacies and mechanisms of candidate hyperaccumulators were provided for the various scenarios of HMM control in CWs. Further, the selection principals, culture methods, and harvest strategies of hyperaccumulator in CWs were discussed. Finally, several perspectives were suggested for the future research. Overall, this review provided guiding information for the utilization of hyperaccumulators in CWs, which can improve the efficiency and sustainability of HMM removal in the CW systems.

The Roles of Plant-Growth-Promoting Rhizobacteria (PGPR)-Based Biostimulants for Agricultural Production Systems

The application of biostimulants has been proven to be an advantageous tool and an appropriate form of management towards the effective use of natural resources, food security, and the beneficial effects on plant growth and yield. Plant-growth-promoting rhizobacteria (PGPR) are microbes connected with plant roots that can increase plant growth by different methods such as producing plant hormones and molecules to improve plant growth or providing increased mineral nutrition. They can colonize all ecological niches of roots to all stages of crop development, and they can affect plant growth and development directly by modulating plant hormone levels and enhancing nutrient acquisition such as of potassium, phosphorus, nitrogen, and essential minerals, or indirectly via reducing the inhibitory impacts of different pathogens in the forms of biocontrol parameters. Many plant-associated species such as Pseudomonas, Acinetobacter, Streptomyces, Serratia, Arthrobacter, and Rhodococcus can increase plant growth by improving plant disease resistance, synthesizing growth-stimulating plant hormones, and suppressing pathogenic microorganisms. The application of biostimulants is both an environmentally friendly practice and a promising method that can enhance the sustainability of horticultural and agricultural production systems as well as promote the quantity and quality of foods. They can also reduce the global dependence on hazardous agricultural chemicals. Science Direct, Google Scholar, Springer Link, CAB Direct, Scopus, Springer Link, Taylor and Francis, Web of Science, and Wiley Online Library were checked, and the search was conducted on all manuscript sections in accordance with the terms Acinetobacter, Arthrobacter, Enterobacter, Ochrobactrum, Pseudomonas, Rhodococcus, Serratia, Streptomyces, Biostimulants, Plant growth promoting rhizobactera, and Stenotrophomonas. The aim of this manuscript is to survey the effects of plant-growth-promoting rhizobacteria by presenting case studies and successful paradigms in various agricultural and horticultural crops.

Interaction of Fe-Mn plaque and Arthrobacter echigonensis MN1405 and uptake and translocation of Cd by Phytolacca acinosa Roxb

In this study, hydroponic experiments were conducted to investigate the role of Fe-Mn plaque and Arthrobacter echigonensis MN1405 under different solution Cd levels (0, 2 and 50 mg L^-1) on Cd uptake and translocation by Phytolacca acinosa Roxb. (P. acinosa). Results showed Cd accumulated by P.acinosa without plaque were mostly distributed in root surface, indicating that an exclusion strategy for Cd tolerance. The formation of Fe-Mn plaque could contribute to the increase in the Cd tolerance of P.acinosa, promotion of the growth, increase in the enhancement of Cd translocation. Among all the treatments, Fe-Mn plaque treatments inoculated with MN1405 accumulated the maximum DCB-Cd (46.61 ± 6.36 g kg^-1) and had the highest value of TF_aeria (2.14 ± 0.01) at 50 mg L^-1 and 2 mg L^-1 solution for Cd, respectively, demonstrating the greatest capacity to accumulate and translocate Cd. The uptake of Cd by P. acinosa in plaque treatments may result in the increase of soluble sugar and decrease of soluble protein synthesized from roots which involved in Cd detoxification and thus diminished the negative effects of Cd to some extent.