A Low Level of NaCl Stimulates Plant Growth by Improving Carbon and Sulfur Assimilation in Arabidopsis thaliana

High-salinity stress represses plant growth by inhibiting various metabolic processes. In contrast to the well-studied mechanisms mediating tolerance to high levels of salt, the effects of low levels of salts have not been well studied. In this study, we examined the growth of Arabidopsis thaliana plants under different NaCl concentrations. Interestingly, both shoot and root biomass increased in the presence of 5 mM NaCl, whereas more than 10 mM NaCl decreased plant biomass. To clarify the biological mechanism by which a low level of NaCl stimulated plant growth, we analyzed element accumulation in plants grown under different NaCl concentrations. In addition to the Na and Cl contents, C, S, Zn, and Cu contents were increased under 5 mM NaCl in shoots; this was not observed at higher NaCl concentrations. Adverse effects of high salinity, such as decreased levels of nitrate, phosphate, sulfate, and some cations, did not occur in the presence of 5 mM NaCl. An increase in C was possibly attributed to increased photosynthesis supported by Cl, Zn, and Cu, which also increased in shoots after NaCl application. Salt stress-responsive gene expression was enhanced under 20 mM NaCl but not at lower doses. Among the S metabolites analyzed, cysteine (Cys) was increased by 5 mM NaCl, suggesting that S assimilation was promoted by this dose of NaCl. These results indicate the usefulness of NaCl for plant growth stimulation.

Assessment of the Macro- and Microelement Composition of Fly Ash from 50-Year-Old Ash Dumps in the Middle Urals (Russia)

The paper considers the macro- and micro- element composition of two ash dumps in the Middle Urals, where meadow and forest communities have been spontaneously forming for 50 years, as well as the effect of the plants on the changing composition of the ash. Higher contents of Cu, Co, Sn, Ga, and Yb were found in the deep ash layers of both dumps, while in the upper 20-cm layer, the trace element composition depended on the influence of different plant communities. Higher contents of Sr, Cr, Ni, Sn, and Co were revealed under meadows, and Ba, Zr, and La were found under the forest. The levels of element accumulation in the aboveground and underground parts of dominant plants were revealed. Increased content of Be, Ce, Ga, La, Sc, Y, and Yb was detected in areas where meadow plants were dominant and Zn and Ba in forest areas. The toxic elements Cd and Pb were highly accumulated in both communities, whereas Co was found only in meadows. The studied materials can serve as a base to assess the feasibility of processing and/or utilizing fly ash from ash dumps in the Middle Urals and similar ash dumps in other regions situated in the southern taiga.

Element Contents in Three Commercially Important Edible Mollusks Harvested off the Southwestern Coast of Crimea (Black Sea) and Assessment of Human Health Risks from Their Consumption

Mollusks are a prospective food for the world’s growing population, but the contents of toxic and essential trace elements in them have not been studied comprehensively. In this work, using inductively coupled plasma mass spectrometry, the contents of 72 elements in soft tissues of the edible mollusks Mytilus galloprovincialis, Rapana venosa, and Crassostrea gigas from the coastal area of the southwestern Crimea were estimated and compared with the maximum permissible levels. Element accumulation similarities were observed in the two bivalve species. Cluster analysis applied to the non-normalized contents allowed finding an optimal number of non-overlapping element clusters: 1 group of macroelements, 1–2 groups of trace elements, and 1–2 groups of ultratrace elements. As an outcome of this analysis, the element accumulation universality index was introduced, which demonstrated the accumulation universality decrease in the order: mussel > sea snail > oyster. An original approach to estimating the mollusk consumption rate was proposed to assess human health risks. Two possible consumption scenarios were identified for Crimean residents. From the expected consumption of all species in both scenarios, there are no health risks, but they are not excluded, within the 95% probability, from high consumption of mussels and sea snails in the pessimistic scenario.