Taurine (TAU) has recently been found to have an impactful role in regulating plant responses under abiotic stresses. This study presented the comparative effects of TAU seed priming and foliar spray application on chickpea plants exposed to hexavalent chromium. Taurine priming and foliar applications (1.6 and 2.4 mM) notably modulated morpho-physiological and biochemical responses of plants under Cr(VI) stress. Plants subjected to 25 mg kg-1 soil Cr in the form of potassium dichromate (K2Cr2O7) displayed a significant reduction in growth, chlorophyll, and uptake of essential nutrients (N, K, P, and Ca). Cr(VI) toxicity also resulted in a notable increase in osmolyte accumulation, lipid peroxidation, relative membrane permeability, ROS generation, antioxidant enzyme activities, antioxidant compounds, endogenous Cr levels, and aerial Cr translocation. Taurine abridged lipoxygenase activity to diminish lipid peroxidation owing to the overproduction of ROS initiated by a higher Cr content. The acquisition and assimilation of essential nutrients were augmented by the TAU-related decrease in leaf and root Cr levels. Consequently, TAU enhanced growth by mitigating oxidative damage, reducing Cr content in the aerial parts, and reinforcing the activities of antioxidant enzymes. Compared to foliar spray, TAU seed priming has demonstrated superior efficacy in mitigating Cr phytotoxicity in plants.

The development of microbial chassis strains with high rare earth element (REE) tolerance is critical for the advancement of new metal biomining and bioprocessing technologies. In this study, we present a mechanistic understanding of how hyperacidophilic bioleaching organism Acidithiobacillus ferrooxidans resists REE-mediated damage at concentrations of REEs as high as 100 mM, while mesophilic Escherichia coli BL21 is significantly inhibited by far lower concentrations of REEs (IC50 between similar to 5 mu M and similar to 140 mu M depending on the element). Using light microscopy to document physiological changes and fluorescent probes to quantify membrane quality, we prove that cell surface interactions explain REE toxicity and demonstrate its reversibility through the addition of chelators. Removal of the A. ferrooxidans outer membrane and cell wall confers REE sensitivity comparable to that of E. coli, corroborating the importance of the outer membrane surface. To conclude, we present a model of differential REE sensitivity in the two strains tested, with implications for industrial metal bioprocessing. IMPORTANCE Demand for rare earth elements (REEs), a technologically critical group of metals, is rapidly increasing (US Geological Survey, 2024. Mineral commodity summaries. Reston, VA). To expand the supply chain without creating environmentally hazardous conditions, there is growing interest in the application of bioprocessing and bioextraction techniques to REE mining and separation. While REE toxicity has been demonstrated in Escherichia coli and other mesophilic neutrophiles, the effect of REEs on organisms currently used in metal bioleaching has been less studied. We present physiological evidence suggesting that REEs damage the outer membrane of E. coli, resulting in growth inhibition that is reversible by chelation. In contrast, Acidithiobacillus ferrooxidans tolerates saturating REE concentrations without apparent inhibition. This study fills gaps in the rapidly expanding body of literature surrounding REE's impact on microbial physiology. Furthermore, A. ferrooxidans resistance to REEs at saturating concentrations (50-100 mM at pH 1.6) is unprecedented in the literature and demonstrates the potential utility of this organism in REE biotechnology.

The use of nanoparticles has emerged as a popular amendment and promising approach to enhance plant resilience to environmental stressors, including salinity. Salinity stress is a critical issue in global agriculture, requiring strategies such as salt-tolerant crop varieties, soil amendments, and nanotechnology-based solutions to mitigate its effects. Therefore, this paper explores the role of plant-based titanium dioxide nanoparticles (nTiO2) in mitigating the effects of salinity stress on soybean phenotypic variation, water content, non-enzymatic antioxidants, malondialdehyde (MDA) and mineral contents. Both 0 and 30 ppm nTiO2 treatments were applied to the soybean plants, along with six salt concentrations (0, 25, 50, 100, 150, and 200 mM NaCl) and the combined effect of nTiO2 and salinity. Salinity decreased water content, chlorophyll and carotenoids which results in a significant decrement in the total fresh and dry weights. Treatment of control and NaCl treated plants by nTiO2 showed improvements in the vegetative growth of soybean plants by increasing its chlorophyll, water content and carbohydrates. Additionally, nTiO2 application boosted the accumulation of non-enzymatic antioxidants, contributing to reduced oxidative damage (less MDA). Notably, it also mitigated Na+ accumulation while promoting K+ and Mg++ uptake in both leaves and roots, essential for maintaining ion homeostasis and metabolic function. These results suggest that nTiO2 has the potential to improve salinity tolerance in soybean by maintaining proper ion balance and reducing MDA level, offering a promising strategy for crop management in saline-prone areas.

Global climate change accelerates the challenges of agricultural drought spells, which are alarming for food security and can trigger food scarcity. Therefore, improving soil-water retention capability and crop drought resilience is becoming more important for sustainable agriculture. This study investigates the individual and combined effects of biochar and potassium on soil water retention, crop drought resilience, and related physio-biochemical mechanisms over a 50-day growth period in potted plants. Pine needle biochar (350 g/10 Kg of soil) was used during the soil preparation stage while potassium sulfate (100 mg/L) was applied as a foliar spray at the development (10 days) and vegetative stages (45 days) under three drought stress conditions: control (100% FC), mild (75% FC) and severe (40% FC). The results revealed that the combined application of biochar and potassium significantly increased morphological, physiological, and biochemical attributes of maize plants under drought stress, improving shoot fresh weight by 11%, 6%, and 5%, root fresh weight by 19%, 19%, and 23%, shoot length by 17%, 16%, and 19%, and root length by 21%, 30%, and 29% under control, mild, and severe drought stress conditions, respectively. Similarly, relative water contents (RWC) increased by 12%, 16%, and 20%, water potential (Psi) increased by 26%, 22%, and 24%, osmotic potential (Psi s) increased by 100%, 59%, and 30%, and turgor potential (Psi p) increased by 28%, 35%, and 51% under combined treatment compared to control, mild, and severe drought stress. Additionally, biochar application with potassium foliar spray also improved membrane stability and integrity, cell wall loosening, membrane lipid peroxidation, and protein denaturing by decreasing electrolytic leakage by 35%, 28%, and 43%, proline by 30%, 27%, and 22%, hydrogen peroxidase by 47%, 45%, and 41%, and malondialdehyde contents by 24%, 20%, and 28% through activation of enzymatic (CAT, POD, SOD) and non-enzymatic (TSS, AsA, GSH) antioxidants. Furthermore, nutrient uptake was enhanced, with N increasing by 47%, 19%, and 45%, P by 64%, 82%, and 52%, and K by 24%, 42%, and 35% in shoots compared to normal, mild, and severe drought stress. These improvements mitigated cell dehydration, reduced transpiration inefficiency and delayed senescence, and ultimately supporting plant growth under drought stress. In conclusion, integrating biochar with potassium application effectively improves soil-water retention, alleviates oxidative stress and enhances drought tolerance in maize plants. This strategy can play a crucial role in sustainable agriculture by mitigating the adverse effects of drought stress and improving food security in drought-prone regions.

Salinity is a major abiotic stress that negatively affects agricultural land, significantly reducing crop yields. It alters the fundamental structure of the soil, causing a decrease in porosity, reduced aeration, and impaired water movement. Piriformospora indica, multifaceted fungi can enhance plant tolerance under abiotic stress conditions. The present study examined the effects of Piriformospora indica on the growth of Solanum melongena L. under saline conditions in a greenhouse, assessing parameters such as proline accumulation, lipid peroxidation, chlorophyll content, stomatal behavior, antioxidant activity, and phenotypic traits under salt stress Results of the present study showed significant improvement in phenotypic traits of Piriformospora indica colonized plants under saline conditions. Solanum melongena L. plants treated with 200 mM NaCl had swollen, deformed guard cells and closed stomata, while colonized plants maintained normal stomatal structure and their stomata remained open. Additionally, untreated plants exhibited higher malondialdehyde levels, indicating greater lipid peroxidation, while Piriformospora indica-colonized plants showed reduced oxidative damage, increased chlorophyll content, and enhanced peroxidase activity under saline conditions. The salt tolerance mediated by Piriformospora indica likely involves lipid desaturation, activation of antioxidant enzymes to counter reactive oxygen species, enhanced metabolism, improved nutrient uptake, proline accumulation, and increased phytohormone production.

Fluoride, a highly phytotoxic and nonessential element in higher concentrations is a major concern in decreasing wheat production. In the present study, we examined the ability of silicon, a semi-essential element which helps to mitigate the detrimental effects of various environmental stresses in overcoming fluoride-mediated toxicity in wheat cultivars. The seeds of two wheat cultivars, tolerant (Raj 4120) and susceptible (Raj 4238), were grown in soil supplemented with NaF (0, 400, and 500 mg kg-1) and then supplied with silicon (0, 200, and 300 mg kg-1) as Na2SiO3 at 10th days of germination with 160 mu mol quanta m-2 s-1 of photon density, 16-h photoperiod, and 55-60% relative humidity at 25 +/- 2 degrees C. The fluoride stress led to oxidative damage in roots, as evidenced by the significant elevation in MDA and H2O2 content in both wheat cultivars and decreased major components of the suberin and cesA4 gene expression in roots, which together can negatively impact the rigidity and strength of the cell wall. Conversely, the application of silicon had a beneficial effect in both wheat cultivars with and without fluoride stress. Silicon decreased the MDA and H2O2 content levels and increased the antioxidant defence system. Interestingly, Si was able to partially reverse F stress in both the wheat cultivars by increasing suberin deposition on the endodermis and promoting secondary cell wall synthesis gene expression in roots. The present study concluded that soil application of silicon can be a useful approach in protecting wheat from fluoride toxicity.

Heavy metal pollution reduces the community of soil microorganisms, including fungi from the genus Trichoderma, which are plant growth promotors and biological control agents. Because of potential effects on crop productivity, the toxic effects of heavy metals (HMs) in Trichoderma are of interest. However, there have been few studies on the biochemical and molecular response to oxidation caused by exposure to copper (Cu), chromium (Cr), and lead (Pb) and whether this antioxidant response is species-specific. In this study, we compared the tolerance of Trichoderma asperellum and Trichoderma longibrachiatum to Cu, Pb, and Cr and evaluated the expression of genes related to the antioxidant response, including glutathione peroxidase (GPX), catalase (CAT), and cysteine synthase (CYS) as well as the activity of peroxidase and catalase. The isolates of Trichoderma were selected because we previously reported them as promotors of plant growth and agents of biological control. Our results revealed that, with exposure to the three HMs, the Trichoderma cultures formed aggregates and the culture color changed according to the metal and the Trichoderma species. The tolerance index (TI) indicated that the two Trichoderma species were tolerant of HMs (Cu > Cr > Pb). However, the TI and conidia production revealed that T. longibrachiatum was more tolerant of HMs than T. asperellum. The three HMs caused oxidative damage in both Trichoderma species, but the enzyme activity and gene expression were differentially regulated based on exposure time (72 and 144 h) to the HMs and Trichoderma species. The main changes occurred in T. asperellum; the maximum expression of the GPX gene occurred at 144 h in response to all three HMs, whereas the CAT gene was upregulated at 72 h in response to Cu but downregulated at 144 h in response to all three HMs. The CYS gene was upregulated in response to the three metals. The peroxidase activity increased with all three HMs, but the catalase activity increased with Cu and Pb at 72 h and decreased at 144 h with Pb and Cr. In T. longibrachiatum, the GPX gene was upregulated with all three HMs at 72 h, the CAT gene was upregulated only with Pb at 72 h and was downregulated at 144 h with HMs. Cr and Cu upregulated CYS gene expression, but expression did not change with Pb. The peroxidase activity increased with Cu at 144 h and with Cr at 72 h, whereas Pb decreased the enzyme activity. In contrast, catalase activity increased with the three metals at 144 h. In conclusion, T. longibrachiatum was more tolerant of Cu, Cr, and Pb than was T. asperellum, but exposure to all three HMs caused oxidative damage to both Trichoderma species. Peroxidases and catalases were activated, and the expression of the genes GPX and CYS was upregulated, whereas the CAT gene was downregulated. These findings indicate that the antioxidant response to HMs was genetically modulated in each Trichoderma species.

Antimony (Sb) is a potential threat to living organisms, but very little is known on strategies manage its toxicity in plants. This study aimed to clarify the role of Fe on alleviation Sb toxicity in a metallicolous population of Salvia spinose and its mechanisms. With regard to the toxicity of Sb in plants and the importance of Fe potential in alleviation of Sb toxicity, S. spinosa was treated with 0 and 27 mg l- 1 Sb (III or V) along with 0, 50 and 300 mu M FeEDTA in a hydroponic system. The plants exposure to iron minimized the uptake of both Sb species by Salvia roots. The limitation of H2O2 generation in response to co-application of Fe with Sb was followed by counterbalancing the antioxidant enzymes (e.g. catalase, superoxide dismutase and ascorbate peroxidase), phenols, flavonoids, lipid membrane preservation, and increase of the carbohydrates and proteins contents, which altogether improved growth in Sb-stressed plants. The Sb (III) toxicity to plants was much higher than Sb (V), but 300 mu M Fe was significantly efficient in reducing Sb damages to Salvia. Altogether, application of Fe could efficiently alleviate the physiological and morphological functions in Sb-stressed Salvia.

Biochar (BC), a charred organic material produced through pyrolysis, has emerged as a promising and an environmentally friendly agro-strategy. This study investigated its potential to mitigate the impacts of global climate change on maize cultivation, specifically focusing on temperature stress tolerance. The research examined how the source material of biochar influences key plant stress mechanisms, including antioxidant enzymes and heat shock proteins (HSPs). To achieve this objective, the study evaluated the effects of biochar derived from three distinct sources-apple orchard pruning waste (PWBC), urban waste (UWBC), and animal manure (AMBC)-on maize plants grown under controlled conditions. A completely randomized factorial design with three replications was employed. Each biochar type was applied at a rate of 4% (w/w) to the soil. The physiological responses of maize plants were assessed under normal (25 degrees C), low (4 degrees C), and high (48 degrees C) temperature conditions. Lipid peroxidation (indicator of oxidative stress), soluble protein content, activity of antioxidant enzymes, and expression levels of HSP70 and HSP90 were analyzed. The results revealed that PWBC application, compared to without BC, significantly reduced malondialdehyde (MDA) accumulation by 38% under both low- and high-temperature stress, suggesting its potential in alleviating oxidative damage. UWBC treatment, on the other hand, demonstrated a pronounced effect on protein metabolism, with soluble protein content increasing by 16% at low and 26% at high temperature. Furthermore, biochar application under temperature stress increased antioxidant enzyme activity, thereby mitigating oxidative stress, with UWBC proving to be the most effective in stimulating antioxidant responses. The expression levels of HSP70 and HSP90 were also significantly regulated by biochar application. UWBC and AMBC treatments displayed the most pronounced effects, with HSP70 expression increasing by 4.6- and 1.6-fold, and HSP90 expression by 8.2- and 45.4-fold, respectively, particularly under high-temperature stress, compared to without BC. These findings indicate that the reduction of lipid peroxidation, activation of antioxidant defense mechanisms, and regulation of HSP70 and HSP90 transcriptional and translational in maize plants under temperature stress vary based on the source material of the biochar. Long-term studies assessing plant yield and quality are recommended to validate these findings further.

Globally, the increasing demand for coal has led to a corresponding rise in the production of fly ash, a by-product of coal combustion. While fly ash has found significant applications in the construction industry due to its pozzolanic properties, its use in agriculture, particularly as a soil amendment or fertilizer, has raised environmental and health concerns. In greenhouse experiments, this study aimed to assess the effects of soils amended with fly ash (FA; 0, 5, 10, 20, 30, 40 and 50%) on Vicia faba L. (faba bean). The experiments were conducted to study the plant growth characteristics, photosynthesis variables, activity of nitrate reductase, damage indicators (reactive oxygen species, malondialdehyde, and cell viability), defense characteristics (proline and antioxidant enzyme activity) and yield parameters. Five replicates of each of the seven treatments were set up in a randomized block design. Among the FA-proportions tested, 40 and 50% caused significant decreases in plant growth characteristics, biochemical and yield attributes. Increases in reactive oxygen species (ROS) and malondialdehyde (MDA) contents corroborated these decreases in the mentioned parameters. However, in soils amended with 5% and 10% FA, plants exhibited significant (p <= 0.05) improvements in the mentioned parameters of growth, photosynthesis, stomata and cell viability, accompanied by the decreased contents of ROS and MDA, and coordinated increases in the activity of superoxide dismutase, catalase and peroxidases. Therefore, we concluded that 10% fly ash dose (lower doses) of FA might be considered an appropriate dose for faba bean cultivation in terms of safe FA utilization practices and sustainable maintenance of the biological and physicochemical health of the soil.