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Phytohormones, including auxin, abscisic acid, gibberellic acid, ethylene, cytokinin, brassinosteroids, salicylic acid, and jasmonic acid, provide beneficial effects for plants against metal(loid) toxicity. However, their mechanisms in alleviating metal(loid) toxicity in plants have not been fully understood. Here, we summarize phytohormone-mediated detoxification mechanisms of metal(loid)s in plants, including As, Cd, Cr, Hg, and Pb. First, we discussed the functions of phytohormones on plant growth and nutrient uptake, and the effects of metal(loid)s on plant growth and hormone contents. We then discussed the underlying mechanisms of selected phytohormones in alleviating metal(loid) toxicity in plants. Those phytohormones protect plants against metal(loid) toxicity mainly by enhancing plant growth, increasing antioxidant capacity, promoting cell wall synthesis and nutrient uptake, and decreasing metal(loid) accumulation. This review highlights the beneficial roles of phytohormones in reducing plant metal(loid) uptake and in enhancing crop yields, which helps to improve crop production and food safety. [ABSTRACT FROM AUTHOR]

The beneficial effects of selenium on As uptake and plant growth in As-hyperaccumulator Pteris vittata are known, but the associated mechanisms remain unclear. Here, we investigated the effects of selenate on arsenic accumulation by P. vittata under two arsenate levels. P. vittata plants were exposed to 13 (As 13) or 133 µM (As 133) arsenate and 5 µM selenate in 0.2-strength Hoagland solution. After 14 d of growth, plant biomass, Se and As content, As speciation, and malondialdehyde (MDA), glutathione reductase (GR), glutathione peroxidase (GPX), and glutathione (GSH and GSSG) levels were determined. The results show that selenate promoted P. vittata growth and increased As concentrations in the roots and fronds by 256% from 97 to 346 mg kg−1 and 142% from 213 to 514 mg kg−1 under As 13 treatment, and by 166% from 500 to 1332 mg kg−1 and 534% from 777 to 4928 mg kg−1 under As 133 treatment. In addition, selenate increased the glutathione content in P. vittata roots and fronds by 75–86% under As 13 treatment and 44–45% under As 133 treatment. Selenate also increased the GPX activity by 161–173%, and GR activity by 72–79% in P. vittata under As 13 and As 133 treatments. The HPLC-ICP-MS analysis indicated that selenate increased both AsIII and AsV levels in P. vittata , with AsIII/AsV ratio being lower in the roots and higher in the fronds, i.e., more AsIII was being translocated to the fronds. Taken together, our results suggest that, via GPX-GR mediated enhancement of GSH-GSSG cycle, selenate effectively increases plant growth and As uptake in P. vittata by improving AsV reduction in the roots and AsIII translocation from the roots to the fronds. [Display omitted] ● Effects of selenate on As uptake and plant growth by P. vittata were investigated. ● Selenate increased P. vittata biomass after 2-wk growth under hydroponics. ● Selenate increased the As concentrations in P. vittata roots and fronds. ● Selenate enhanced AsV reduction, with elevated AsIII being in the fronds. ● Selenate enhanced GR and GPX activities and glutathione levels in P. vittata. [ABSTRACT FROM AUTHOR]

It is known that selenium (Se) enhances plant growth and arsenic (As) accumulation in As-hyperaccumulator Pteris vittata, but the associated mechanisms are unclear. In this study, P. vittata was exposed to 50 μM arsenate (AsV) under hydroponics plus 25 or 50 μM foliar selenate. After 3-weeks of growth, the plant biomass, As and Se contents, As speciation, malondialdehyde (MDA) and glutathione (GSH and GSSG) levels, and important genes related to As-metabolism in P. vittata were determined. Foliar-Se increased plant biomass by 17 − 30 %, possibly due to 9.1 − 19 % reduction in MDA content compared to the As control. Further, foliar-Se enhanced the As contents by 1.9–3.5 folds and increased arsenite (AsIII) contents by 64 − 136 % in the fronds. The increased AsV reduction to AsIII was attributed to 60 − 131 % increase in glutathione peroxidase activity, which mediates GSH oxidation to GSSG (8.8 −29 % increase) in the fronds. Further, foliar-Se increased the expression of AsIII antiporters PvACR3;1–3;3 by 1.6 − 2.1 folds but had no impact on phosphate transporters PvPht1 or arsenate reductases PvHAC1/2. Our results indicate that foliar-Se effectively enhances plant growth and arsenic accumulation by promoting the GSH-GSSG cycle and upregulating gene expression of AsIII antiporters, which are responsible for AsIII translocation from the roots to fronds and AsIII sequestration into the fronds. The data indicate that foliar-Se can effectively improve phytoremediation efficiency of P. vittata in As-contaminated soils. [Display omitted] • Foliar-Se promoted plant growth by 17 − 30 % via decreasing MDA in the fronds. • Foliar-Se enhanced the As accumulation by 1.9–3.5 folds in the fronds. • Foliar-Se increased the glutathione oxidation from GSH to GSSG in the fronds. • Foliar-Se upregulated PvACR3;1-3;3 by 2-fold for As translocation & sequestration. [ABSTRACT FROM AUTHOR]

This paper presents a modified domain decomposition method for the numerical solution of discrete Hamilton-Jacobi-Bellman equations arising from a class of optimal control problems using diffusion models. A convergence theorem is established. Numerical results indicate the effectiveness and accuracy of the method. [ABSTRACT FROM AUTHOR]

In contaminated soils, arsenic (As) often co-exists with copper (Cu). However, its effects on As accumulation and the related mechanisms in As-hyperaccumulator Pteris vittata remain unclear. In this study, P. vittata plants were exposed to 50 µM As and/or 50 µM Cu under hydroponics to investigate the effects of Cu on plant growth and As accumulation, as well as gene expression related to arsenic uptake (P transporters), reduction (arsenate reductases), and translocation and sequestration (arsenite antiporters). After 14 d of growth and compared to the As treatment, the As concentration in P. vittata fronds increased by 1.4-times from 793 to 1131 mg·kg−1 and its biomass increased by 1.2-fold from 18.0 to 21.1 g·plant−1 in the As+Cu treatment. Copper-enhanced As accumulation was probably due to upregulated gene expressions related to As-metabolisms including As uptake (1.9-fold in P transporter PvPht1;3), translocation (2.1–2.4 fold in arsenite antiporters PvACR3/3;2) and sequestration (1.5–2.0 fold in arsenite antiporters PvACR3;1/3;3). Our results suggest that moderate amount of Cu can help to increase the As accumulation efficiency in P. vittata , which has implication in its application in phytoremedation in As and Cu co-contaminated soils. [Display omitted] • 50 µM Cu enhanced plant growth and As accumulation in P. vittata. • P. vittata maintains a normal Cu level in fronds by concentrating most Cu in roots. • Cu promoted AsV uptake by upregulating P transporter PvPht1;3. • Cu upregulated AsIII antiporters PvACR3-3;3 for As translocation and sequestration. [ABSTRACT FROM AUTHOR]