Hydrogen peroxide pretreatment assisted phytoremediation of sodium dodecyl sulfate by Juncus acutus L

Synergistic effects of Fe3O4-NPs and Enterobacter cloacae in alleviating mercury stress in wheat (Triticum aestivum L.): Insights into morpho-physio-biochemicals attributes

In the current industrial scenario, mercury (Hg) as a metal is of great importance but poses a major threat to the ecosystem because of its toxicity, but fewer studies have been conducted on its effects and alleviation strategies by using nanoparticles (NPs) and plant growth promoting rhizobacteria (PGPR). Taking into consideration the positive effects of iron oxide (Fe3O4)⎯NPs and Enterobacter cloacae rhizobacteria in reducing Hg toxicity in plants, the present study was conducted. A pot experiment was conducted over 60 days using wheat (Triticum aestivum L.) to investigate the effects of varying Hg levels (0, 50 and 100 mg kg⎯1) combined with different concentrations of Fe3O4-NPs (25 and 50 mg L-1) and E. cloacae (10 and 20 ppm) on various morpho-physio-biochemical responses. The research outcomes indicated that elevated levels of Hg stress in the soil significantly (P < 0.05) decreased plant growth and biomass, photosynthetic pigments, nutrients uptake and gas exchange attributes. However, Hg stress also induced oxidative stress in the plants by increasing malondialdehyde (MDA) and hydrogen peroxide (H2O2), which also induced increased compounds of various enzymatic and non-enzymatic antioxidants and also the gene expression and sugar content. Furthermore, a significant (P < 0.05) increase in proline metabolism, the ascorbate-glutathione (AsA-GSH) cycle were observed. Although, the application of Fe3O4-NPs and E. cloacae showed a significant (P < 0.05) increase in plant growth and biomass, nutrients uptake, gas exchange characteristics, enzymatic and non-enzymatic compounds, and their gene expression and also decreased oxidative stress. In addition, the application of Fe3O4-NPs and E. cloacae enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in T. aestivum seedlings. Research findings, therefore, suggest that the application of Fe3O4-NPs and E. cloacae can ameliorate Hg toxicity in T. aestivum seedlings, resulting in improved plant growth and composition under metal stress, as depicted by balanced antioxidant defense mechanism.

Enhancement of the phytoremediation performance in heavy metal-contaminated soil using a multifunctional EPS-producing bacterium Kosakonia sp. W18

The use of exopolysaccharide (EPS)-producing bacteria for the phytoremediation of heavy metal-contaminated soil is emerging as a promising approach. This study explores the potential of Kosakonia sp. W18, an EPS-producing bacterium isolated from Suaeda japonica habitat, in the phytoremediation of heavy metal-contaminated soils. Strain W18 exhibited the highest tolerance to Pb (EC50 of 231.1 mg L-1), Cu, and Cr (EC50 of 24.9 and 26.7 mg L-1), and displayed plant growth-promoting traits. The EPS extracted from W18 (107.3 mg L-1) showed 58% emulsification against chloroform, remarkable 2,2-Diphenyl-1-picrylhydrazyl (38%) and hydroxyl radical (83%) scavenging activities. Extracted EPS also exhibited a Pb-removal efficiency exceeding 79%, with an adsorption capacity for Pb of 499.2 ± 7.7 mg·g-EPS-1. In the contaminated soils with Pb (500 mg kg-1) and Cr (100 mg kg-1), W18 inoculation significantly enhanced pakchoi shoot length and biomass by 1.1-1.3 times after 20 days. The presence of pakchoi decreased bioavailable Pb and Cr concentrations in soil by 46%, which elevated to 76% for Pb and 72% for Cr post-inoculation with W18. Furthermore, W18 enhanced Pb uptake in pakchoi roots, increasing the bioconcentration factor by over 1.5 times and large macroaggregates (>2 mm) formation exceeded 75%. Overall, this study highlights Kosakonia sp. W18's multifunctional abilities to promote pakchoi growth and improve its effectiveness in phytoremediation of heavy metals in contaminated soils.

Priming agents combat copper stress in wheat (Triticum aestivum L.) under hydroponic conditions: Insights in impacts on morpho-physio-biochemical traits and health risk assessment

In recent years, the use of priming agents, such as silicon, melatonin, salicylic acid, glycine betaine, and ascorbic acid has gained significant attention for their role in mitigating abiotic stresses across various plant species. While previous research has been conducted on the individual impact of silicon, melatonin, salicylic acid, glycine betaine, and ascorbic acid in metal stress resistance among various crop species, their combined effects in the context of heavy metal stressed conditions remain underexplored. Wheat (Triticum aestivum L.) seedlings was grown under the toxic concentration of copper (Cu) i.e., 100 µM which were applied with silicon, melatonin, salicylic acid, glycine betaine, and ascorbic acid under hydroponic conditions for 21 days. The research outcomes indicated that the toxic concentration of Cu in the nutrient solution notably reduced plant growth and biomass, photosynthetic pigments, and gas exchange attributes. However, Cu stress also induced oxidative stress in the plants by increasing malondialdehyde (MDA), hydrogen peroxide (H2O2) which also induced increased compounds of various enzymatic and non-enzymatic antioxidants, health risk index (HRI) and also the gene expression and sugar content. Furthermore, a significant increase in proline metabolism, the AsA-GSH cycle, and the pigmentation of cellular components was observed. Although, the application of different priming agents, such as silicon, melatonin, salicylic acid, glycine betaine, and ascorbic acid showed a significant increase in plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds, and their gene expression and also decreased oxidative stress and HRI. In addition, the application of different priming agents enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in T. aestivum seedlings. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Innovative auxin-micronutrient based nanocomposites (IAA-Fe2O3NPs and IAA-Mn2O3NPs) shield strawberry plants from lead toxicity

Smart nanohybrid technology with potential advantages to plants has recently been developed formanaging the widespread pollution of heavy metals. Herein, we disclose a novel strategy to combat Pb stress in strawberry (Fragaria spp. cv. Fertona) through a newly designed nano-based system that conjugates indole acetic acid (IAA) with nanoparticles (NPs) of iron (Fe) and manganese (Mn) micronutrients, forming IAA-Mn2O3NPs (IAA-MnNPs) and IAA-Fe2O3NPs (IAA-FeNPs) nanocomposites and illuminates the underlying mechanisms involved. NPs were synthesized, yielding cubic Mn2O3 NPs (50 nm) and spheric Fe2O3 NPs (30-40 nm), and evidenced by various characterization techniques. The incorporation of IAA hormone to the surface of NPs was examined using FT-IR spectroscopy. Results showed that Pb harshly hindered strawberry growth and promoted stress oxidative markers, i.e., MDA and ROS byproducts. Notably, the application of IAA-MnNPs and IAA-FeNPs at 50 and 100 ppm moderated the deleterious effects of Pb toxicity in strawberry plants, as revealed by enhanced growth indices, photosynthetic traits, membrane stability, and nutrient profiles of Mn and Fe, as well as higher IAA accumulation. This is pertinent to lessen Pb accumulation and impaired Pb-induced oxidative stress. The decrease in Pb content holds to be filled in with escalating Pb-detoxification mechanisms by enhancing enzymatic antioxidants' activities such as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione S-transferases (GST), phenylalanine ammonia-lyase (PAL), nitrate reductase (NR), and attenuating polyphenol oxidase (PPO). On top of that, IAA-MnNPs and IAA-FeNPs elevated the content of non-enzymatic antioxidants, e.g., ascorbic acid and flavonoids, and enhanced the accumulation of chelating agents, i.e., proline, glutathione, and phytochelatins. We posit that the novel-engineered IAA-MnNPs and IAA-FeNPs nanohybrids present an effective approach that could fend off Pb stress in strawberry plants in contaminated croplands.

Protective effects of the exogenous application of salicylic acid and chitosan on chromium-induced photosynthetic capacity and osmotic adjustment in Aconitum napellus

Chitosan (CTS) is recognized for enhancing a plant's resilience to various environmental stresses, such as salinity and drought. Moreover, salicylic acid (SA) is acknowledged as a growth regulator involved in addressing metal toxicity. However, the effectiveness of both compounds in mitigating Cr-induced stress has remained relatively unexplored, especially in the case of Aconitum napellus, a medicinally and floricultural important plant. Therefore, the primary objective of this study was to investigate the potential of CTS and SA in alleviating chromium (Cr)-induced stress in A. napellus. To address these research questions, we conducted a controlled experiment using potted plants to evaluate the individual and combined impacts of CTS and SA on plants exposed to Cr stress. Foliar application of CTS (0.4 g/L) or SA (0.25 mmol/L) led to significant improvements in the growth, chlorophyll content, fluorescence, and photosynthetic traits of A. napellus plants under Cr stress. The most notable effects were observed with the combined application of CTS and SA, resulting in increases in various morphological parameters, such as shoot length (2.89% and 7.02%) and root length (27.75% and 3.36%) under the Cr 1 and Cr 2 treatments, respectively. Additionally, several physiological parameters, such as chlorophyll a (762.5% and 145.56%), chlorophyll b (762.5% and 145.56%), carotenoid (17.03% and 28.57%), and anthocyanin (112.01% and 47.96%) contents, were notably improved under the Cr 1 and Cr 2 treatments, respectively. Moreover, the combined treatment of CTS and SA improved the fluorescence parameters while decreasing the levels of enzymatic antioxidants such as catalase (27.59% and 43.79%, respectively). The application also notably increased osmoprotectant parameters, such as the total protein content (54.11% and 20.07%) and the total soluble sugar content (78.17% and 49.82%) in the leaves of A. napellus in the Cr 1 and 2 treatments, respectively. In summary, these results strongly suggest that the simultaneous use of exogenous CTS and SA is an effective strategy for alleviating the detrimental effects of Cr stress on A. napellus. This integrated approach opens promising avenues for further exploration and potential implementation within agricultural production systems.

Phyto-treatment of tannery industry effluents under combined application of citric acid and chromium-reducing bacterial strain through Lemna minor L.: A lab scale study

Contamination of agricultural soils with heavy metals (HMs) poses a significant environmental threat, especially because industrial discharges often irrigate agricultural lands. A prominent source of HM(s) pollution occurs from tannery effluents containing high concentrations of chromium (Cr) in both Cr3+ and Cr6+ forms along with other toxic materials. Cr is known for its carcinogenic and mutagenic properties in biological systems. Microbe-assisted phytoremediation has emerged as a promising and environmentally friendly approach for detoxifying Cr-contaminated environments. This study aimed to evaluate the performance of citric acid (CA) and a Cr-reducing bacterial strain (Staphylococcus aureus) on the phytoextraction potential of Lemna minor within a Constructed Wetland System treated with tannery wastewater. Various combinations of tannery wastewater (0, 50, and 100 %), CA (0, 5 and 10 mM), and microbial inoculants were applied to the test plants. The mitigative effects of Staphylococcus aureus strain K1 were examined in combination with different concentrations of CA (0, 5, 10 mM). Data on growth and yield attributes highlighted the beneficial effects of bacterial inoculation and CA in ameliorating Cr toxicity in L. minor, as evidenced by increased foliar chlorophyll and carotenoid contents, enhanced antioxidant enzyme activities (SOD, POD, APX, CAT), and improved nutrient uptake. Specifically, CA application resulted in an enhancement of Cr ranging from 12% to 15% and 23%-31% in concentration, and 134%-141% and 322%-337% in Cr accumulation, respectively. When combined with the S. aureus inoculation treatment, CA application (5 and 10 mM) further increased the concentration and accumulation of Cr in L. minor. The enhancement in Cr ranged from 12% to 23% and 27%-41% in concentration, 68%-75%, and 179%-185% in accumulation, respectively. These results demonstrated that L. minor is an effective choice for environmentally friendly Cr remediation due to its continued ability to grow in polluted wastewater. This study suggested that microbial-assisted phytoextraction combined with chelating agents such as CA could be a practical and effective approach for remediating tannery effluents.

Physiological and molecular analysis of pitaya (Hylocereus polyrhizus) reveal up-regulation of secondary metabolites, nitric oxide, antioxidant defense system, and expression of responsive genes under low-temperature stress by the pre-treatment of hydrogen peroxide

Low-temperature events are one of the leading environmental cues that considerably reduce plant growth and shift species biodiversity. Hydrogen peroxide (H2O2) is a signaling molecule that has a distinguished role during unfavorable conditions and shows outstanding perspectives in low-temperature stress. Herein, we elucidated the protective role and regulatory mechanism of H2O2 in alleviating the deleterious effects of low-temperature stress in pitaya plants. Micropropagated pitaya plants were cultured in Murashige and Skoog media supplemented with different levels of H2O2 (0, 5, 10, and 20 mM) and then exposed to low-temperature stress (5 °C for 24 h). H2O2 at 10 mM, improved low-temperature stress tolerance by relieving oxidative injuries and ameliorating growth parameters in terms of fresh weight (66.7%), plant length (16.7%), and pigments content viz., chlorophyll a (157.4%), chlorophyll b (209.1%), and carotenoids (225.9%). H2O2 counteracted the low-temperature stress by increasing amino acids (224.7%), soluble proteins (190.5%), and sugars (126.6%). Simultaneously, secondary metabolites like ascorbic acid (ASA), anthocyanins, phenolics, flavonoids, total antioxidant (TOA), and proline were also up-regulated by H2O2 (104.9%, 128.8%, 166.3%, 141.4%, and 436.4%, respectively). These results corresponded to the stimulative role triggered by H2O2 in boosting the activities of catalase (22.4%), ascorbate peroxidase (20.7%), superoxide dismutase (88.4%), polyphenol oxidase (60.7%), soluble peroxidase (23.8%), and phenylalanine ammonia-lyase (57.1%) as well as the expression level of HpCAT, HpAPX, HpSOD, HpPPO, and HpPAL genes, which may help to moderate low-temperature stress. In conclusion, our findings stipulate new insights into the mechanisms by which H2O2 regulates low-temperature stress tolerance in pitaya plants.

Mitigation effect of alpha-tocopherol and thermo-priming in Brassica napus L. under induced mercuric chloride stress

Soil pollution with heavy metals has grown to be a big hassle, leading to the loss in farming production particularly in developing countries like Pakistan, where no proper channel is present for irrigation and extraction of these toxic heavy metals. The present study aims to ameliorate the damages caused by heavy metal ions (Hg-Mercury) on rapeseed (Brassica napus L.) via a growth regulator (α-tocopherol 150 mg/L) and thermopriming technique at 4 °C and 50 °C to maintain plant agronomical and physiological characteristics. In pot experiments, we designed total of 11 treatments viz.( T0 (control), T1 (Hg4ppm), T2 (Hg8ppm), T3 (Hg4ppm + 4 °C), T4 (Hg4ppm + 4 °C + tocopherol (150 m/L)), T5 (Hg4ppm + 50 °C), T6 (Hg4ppm + 50 °C + tocopherol (150 mg/L)), T7 (Hg8ppm + 4 °C), T8 (Hg8ppm + 4 °C + tocopherol (150 mg/L)), T9 (Hg8ppm + 50 °C), T10 (Hg8ppm + 50 °C + tocopherol (150 mg/L) the results revealed that chlorophyll content at p < 0.05 with growth regulator and antioxidant enzymes such as catalase, peroxidase, and malondialdehyde enhanced up to the maximum level at T5 = Hg4ppm + 50 °C (50 °C thermopriming under 4 ppm mercuric chloride stress), suggesting that high temperature initiate the antioxidant system to reduce photosystem damage. However, protein, proline, superoxide dismutase at p < 0.05, and carotenoid, soluble sugar, and ascorbate peroxidase were increased non-significantly (p > 0.05) 50 °C thermopriming under 8 ppm high mercuric chloride stress (T9 = Hg8ppm + 50 °C) representing the tolerance of selected specie by synthesizing osmolytes to resist oxidation mechanism. Furthermore, reduction in % MC (moisture content) is easily improved with foliar application of α-tocopherol and 50 °C thermopriming and 4 ppm heavy metal stress at T6 = Hg4ppm + 50 °C + α-tocopherol (150 mg/L), with a remarkable increase in plant vigor and germination energy. It has resulted that the inhibitory effect of only lower concentration (4 ppm) of heavy metal stress was ameliorated by exogenous application of α-tocopherol and thermopriming technique by synthesizing high levels of proline and antioxidant activities in maintaining seedling growth and development on heavy metal contaminated soil.

Reactive Oxygen Species: A Crosslink between Plant and Human Eukaryotic Cell Systems

Reactive oxygen species (ROS) are important regulating factors that play a dual role in plant and human cells. As the first messenger response in organisms, ROS coordinate signals in growth, development, and metabolic activity pathways. They also can act as an alarm mechanism, triggering cellular responses to harmful stimuli. However, excess ROS cause oxidative stress-related damage and oxidize organic substances, leading to cellular malfunctions. This review summarizes the current research status and mechanisms of ROS in plant and human eukaryotic cells, highlighting the differences and similarities between the two and elucidating their interactions with other reactive substances and ROS. Based on the similar regulatory and metabolic ROS pathways in the two kingdoms, this review proposes future developments that can provide opportunities to develop novel strategies for treating human diseases or creating greater agricultural value.