The purpose of the present study is to investigate the role of hydrogen sulfide (H2S), in improving resistance to common bean salt stress. Method shows that common bean seeds were soaked in water and in two concentrations of sodium hydrosulfide (50 and 100 µM) for 8 h. After 25 days from sowing, the pots were irrigated with water and with two concentrations of NaCl (75 and 150 mM) until the end of the experiment. Results revealed that H2S relieved salt stress by decreasing growth inhibition and photosynthetic characteristics, and increasing osmolyte contents (proline and glycine betaine). Furthermore, H2S reduced oxidative damage by lowering lipid peroxidation, electrolyte leakage, and reactive oxygen species production such as hydrogen peroxide, hydroxyl radicals, and superoxide anion by increasing non-enzymatic antioxidants such as ascorbic acid and glutathione, as well as enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), and nitrate reductase (NR). Meanwhile, salt stress and H2S application increased the endogenous level of H2S, which was accompanied by an increase in nitric oxide concentration. H2S, in particular, maintained sodium (Na+) and potassium (K+) homeostasis in the presence of excess NaCl. In general, H2S effectively reduced oxidative stress in common bean plants by increasing relative expression levels of copper-zinc superoxide dismutase (Cu-ZnSOD), CAT, and glutathione S-transferase (GST). Applying H2S to common bean plants could protect them from salinity stress by maintaining the Na+/K+ balance, boosting endogenous H2S and nitric oxide levels, and preventing oxidative damage by increasing antioxidant activity.

Purpose This research studies the alleviation potential of N- or/and P- deprived Coccomyxa chodatii SAG 216–2 extracts as biostimulants on mercury stress (10 and 30 mg L−1) of wheat seedlings. Materials The study includes the interactive effect of mercury and biostimulants on growth, reactive nitrogen and oxygen species, membrane stability, and antioxidant activity in wheat seedlings. Results The imposed toxic effects of Hg-stress on the studied parameters were to a great extent less noticeable under different algal extracts, and the magnitude of augmentation was P-deprived extract > P-&N-deprived extract > N-deprived extract > Normal algal extract. Higher Hg-tolerance modulated by algal extracts, especially P-deprived extract, was associated with high antioxidant capacity and ferric reducing power. These activities could instigate the antioxidant system (enzymatic and non-enzymatic) under Hg-stress. Furthermore, the algal extracts broadly alleviated wheat chelating mechanism deterioration by Hg-stress via enhancing phytochelatins, reduced glutathione, and metallothioneins. Thus, the applied algal extracts retarded Hg accumulation in wheat tissues exposed to Hg stress. In addition, the nitrosative stress induced by Hg-stress in terms of high nitric oxide content was minimized by various algal extracts. All these regulations by algal extracts are reflected in high membrane stability as denoted by the reduction of lipid peroxidation, lipoxygenase, and methylglyoxal as a sign of reducing oxidative damage and reactive oxygen species (ROS). Conclusion Thus, we recommended using the macronutrient-deprived algal extracts of Coccomyxa chodatii SAG 216–2 as potential biostimulants of wheat growth under Hg-stress and may be under other stresses.

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Short-and long-terms stimulatory impacts of calcium oxide nanoparticles (CaONPs) on the growth, photosynthesis and antioxidant enzymes of Chlorella sp.

In this work, tuning oxygen tension was targeted to improve hydrogen evolution. To achieve such target, various consortia of the chlorophyte Coccomyxa chodatii with a newly isolated photosynthetic purple non-sulfur bacterium (PNSB) strain Rhodobium gokarnense were set up, sulfur replete/deprived, malate/acetate fed, bicarbonate/sulfur added at dim/high light. C. chodatii and R. gokarnense are newly introduced to biohydrogen studies for the first time. Dim light was applied to avoid the inhibitory drawbacks of photosynthetic oxygen evolution, values of hydrogen are comparable with high light or even more and thus economically feasible to eliminate the costs of artificial illumination. Particularly, the consortium of 2n− (n = 1.9 × 105 cell/ml, sulfur deprived) demonstrated its perfection for the target, i.e., the highest possible cumulative hydrogen. This consortium exhibited negative photosynthesis, i.e., oxygen uptake in the light. Most hydrogen in consortia is from bacterial origin, although algae evolved much more hydrogen than bacteria on per cell basis, but for only one day (the second 24 h), as kinetics revealed. The higher hydrogen in unibacterial culture or consortia results from higher bacterial cell density (20 times). Consortia evolved more hydrogen than their respective separate cultures, further enhanced when bicarbonate and sulfur were supplemented at higher light. The share of algae relatively increased as bicarbonate or sulfur were added at higher light intensity, i.e., PSII activity partially recovered, resulting in a transient autotrophic hydrogen evolution. The addition of acetic acid in mixture with malic acid significantly enhanced the cumulative hydrogen levels, mostly decreased cellular ascorbic acid indicating less oxidative stress and relief of PSII, relative to malic acid alone. Starch, however, decreased, indicating the specificity of acetic acid. Exudates (reducing sugars, amino acids, and soluble proteins) were detected, indicating mutual utilization. Yet, hydrogen evolution is limited; tuning PSII activity remains a target for sustainable hydrogen production.

The extensive use of nanoparticles (NPs) in diverse applications causes their localization to aquatic habitats, affecting the metabolic products of primary producers in aquatic ecosystems, such as algae. Synthesized calcium oxide nanoparticles (CaO NPs) are of the scarcely studied NPs. Thus, the current work proposed that the exposure to CaO NPs may instigate metabolic pathway to be higher than that of normally growing algae, and positively stimulate algal biomass. In this respect, this research was undertaken to study the exposure effect of CaO NPs (0, 20, 40, 60, 80, and 100 µg mL −1 ) on the growth, photosynthesis, respiration, oxidative stress, antioxidants, and lipid production of the microalga Coccomyxa chodatii SAG 216-2. The results showed that the algal growth concomitant with chlorophyll content, photosynthesis, and calcium content increased in response to CaO NPs. The contents of biomolecules such as proteins, amino acids, and carbohydrates were also promoted by CaO NPs with variant degrees. Furthermore, lipid production was enhanced by the applied nanoparticles. CaO NPs induced the accumulation of hydrogen peroxide, while lipid peroxidation was reduced, revealing no oxidative behavior of the applied nanoparticles on alga. Also, CaO NPs have a triggering effect on the antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase. The results recommended the importance of the level of 60 µg mL −1 CaO NPs on lipid production (with increasing percentage of 65% compared to control) and the highest dry matter acquisition of C. chodatii. This study recommended the feasibility of an integrated treatment strategy of CaO NPs in augmenting biomass, metabolic up-regulations, and lipid accumulation in C. chodatii.