Polyamines (PAs) are signaling molecules that exhibit promising roles in improving stress tolerance in plants. Limited information is available concerning the effects of the exogenous PAs on medicinal plants including chamomile. This experiment was carried out to study the effects of foliar application of PAs [Putrescine (Put), Spermidine (Spd), and Spermine (Spm)] on physiological and biochemical processes to understand the possible mechanisms concerning the water deficit stress [soil Field Capacity (FC) as control, 80% of FC (FC80), and 60% of FC (FC60)] alleviation in German Chamomile. We found that PAs partially inhibited water deficit-induced stomatal closure and induced antioxidant enzymes to eliminate the increased H2O2. Spd increased stomatal conductance (g(s)) by 66, 65, and 35% at FC, FC80, and FC60, respectively, compared with the control. The increased g(s) enhanced leaf net photosynthesis (A(N)) by 52 and 86% at FC80 and FC60, respectively, compared with the control. The role of PAs in oxidative damage alleviation was approved by the negative correlation of leaf antioxidant activities and Malondialdehyde (MDA) and H2O2 content. According to the results, PAs function as stress-protecting compounds to instigate the antioxidative enzymes to scavenge stress-induced H2O2, improve membrane stability, and enhance water deficit tolerance. Generally, our results suggested that PAs could be potential growth regulators to alleviate mild to severe water deficit stress.

Chromium (Cr) contamination in soils reduces crop yields and poses a remarkable risk to human and plant system. The main objective of this study was to observe the protective mechanisms of exogenously applied melatonin (Mel- 0.05, 0.1, and 0.15 mu M) in seedlings of Brassica juncea L. under Cr (0.2 mM) stress. This was accomplished by analysing the plant ' s morpho-physiological, biochemical, nuclear, membrane, and cellular characteristics, as well as electrolyte leakage. Superoxide, malondialdehyde, and hydrogen peroxide increased with Cr toxicity. Cr also increased electrolyte leakage. Seedlings under Cr stress had 86.4% more superoxide anion and 27.4% more hydrogen peroxide. Electrolyte leakage increased 35.7% owing to Cr toxicity. B. juncea L. cells with high radical levels had membrane and nuclear damage and decreased viability. Besides this, the activities of the antioxidative enzymes, as POD, APOX, SOD, GST, DHAR, GPOX and GR also elevated in the samples subjected to Cr toxicity. Conversely, the activity of catalase was downregulated due to Cr toxicity. In contrast, Mel reduced oxidative damage and conserved membrane integrity in B. juncea seedlings under Cr stress by suppressing ROS generation. Moreover, the activity of antioxidative enzymes that scavenge reactive oxygen species was substantially upregulated by the exogenous application of Mel. The highest concentration of Mel (Mel c- 0.15 mu M) applied showed maximum ameliorative effect on the toxicity caused by Cr. It causes alleviation in the activity of SOD, CAT, POD, GPOX, APOX, DHAR, GST and GR by 51.32%, 114%, 26.44%, 48.91%, 87.51%, 149%, 42.30% and 40.24% respectively. Histochemical investigations showed that Mel increased cell survival and reduced ROS-induced membrane and nuclear damage. The findings showed that Mel treatment upregulated several genes, promoting plant development. Its supplementation decreased RBOH1 gene expression in seedling sunder stress. The results supported the hypothesis that Mel concentrations reduce Cr-induced oxidative burst in B. juncea.

Background The bacterial mechanisms responsible for hydrogen peroxide (H2O2) scavenging have been well-reported, yet little is known about how bacteria isolated from cold-environments respond to H2O2 stress. Therefore, we investigated the transcriptional profiling of the Planomicrobium strain AX6 strain isolated from the cold-desert ecosystem in the Qaidam Basin, Qinghai-Tibet Plateau, China, in response to H2O2 stress aiming to uncover the molecular mechanisms associated with H2O2 scavenging potential. Methods We investigated the H2O2-scavenging potential of the bacterial Planomicrobium strain AX6 isolated from the cold-desert ecosystem in the Qaidam Basin, Qinghai-Tibet Plateau, China. Furthermore, we used high-throughput RNA-sequencing to unravel the molecular aspects associated with the H2O2 scavenging potential of the Planomicrobium strain AX6 isolate. Results In total, 3,427 differentially expressed genes (DEGs) were identified in Planomicrobium strain AX6 isolate in response to 4 h of H2O2 (1.5 mM) exposure. Besides, Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology analyses revealed the down- and/or up-regulated pathways following H2O2 treatment. Our study not only identified the H2O2 scavenging capability of the strain nevertheless also a range of mechanisms to cope with the toxic effect of H2O2 through genes involved in oxidative stress response. Compared to control, several genes coding for antioxidant proteins, including glutathione peroxidase (GSH-Px), Coproporphyrinogen III oxidase, and superoxide dismutase (SOD), were relatively up-regulated in Planomicrobium strain AX6, when exposed to H2O2. Conclusions Overall, the results suggest that the up-regulated genes responsible for antioxidant defense pathways serve as essential regulatory mechanisms for removing H2O2 in Planomicrobium strain AX6. The DEGs identified here could provide a competitive advantage for the existence of Planomicrobium strain AX6 in H2O2-polluted environments.

Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H2O2 and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease's control. Wheat plants from -Si and HN and +Si and LN treatments recorded lower tan spot severity.

The aim of this research was to determine the impact of hydrogen peroxide spraying and ozone gas fumigation during the growing season of tomato plants grown under cover on the mechanical and chemical parameters of fruit harvested from these plants. Tomato plants were grown under cover in accordance with the principles of good agricultural practice in the soil and climatic conditions of southeastern Poland. During the growing season, tomato fruits were collected for testing in order to determine the impact of the applied variable factors on the modification of selected metabolic pathways of bioactive compounds. As part of the tests on the chemical properties of the fruits, the content of ascorbic acid, the total content of polyphenols, and the antioxidant potential were determined. Additionally, the influence of the tested variable factors on the mechanical properties of tomato fruits was determined. In the case of the total polyphenol content, the most beneficial effects were observed for fruits collected from plants treated with ozonation at a dose of 2 ppm for 3 min and spraying the plants with 1% hydrogen peroxide. The highest antioxidant potential was recorded for fruits of the variants ozonated with doses of 2 ppm for 1 min, 2 ppm for 1.5 min, and 2 ppm for 3 min compared to the remaining variants and controls. In turn, the vitamin C content increased significantly in the tested fruits after the ozonation of plants with a dose of 2 ppm for 1 min and ozonation with a dose of 2 ppm for 3 min combined with spraying plants with 3% hydrogen peroxide. In the case of the mechanical properties of tomato fruits, only the ozonation dose of 2 ppm for 3 min significantly improved them.

Silicon (Si) as silicic acid, Si(OH)4 offers several benefits to the growth of plants, especially under adverse environmental conditions. Therefore, the present study aimed to assess the role of exogenous Si treatments (0.5 and 1.0 mM) in the tolerance of Fagopyrum esculentum Moench to Al stress applied at two different concentrations (0.2 and 0.4 mM). A set of agrophysiological, biochemical and antioxidant parameters were evaluated during the investigation. The exogenous Si application to Fagopyrum esculentum plants exposed to Al treatments significantly modulated the physiological and antioxidant responses to overcome the Al phytotoxicity and provide beneficial effects. The results indicated that the application of different doses of Al significantly affected the physiological parameters viz., plant growth, tolerance index, biomass accumulation (BA), relative water content (RWC), lipid peroxidation (LP), membrane stability index (MSI) and reduced glutathione (GSH) content. Likewise, aluminum -treated leaves also displayed increased hydrogen peroxide accumulation signifying the extent of the damage in F. esculentum. However, the individual and combined doses of silicon (Si) yielded beneficial effects on the physiological and antioxidant attributes. Multivariate analysis also suggested that individual and combined doses of Si improved physiological (root length (RL), shoot length (SL), root and shoot tolerance index (TI), BA, RWC, MSI and osmolytes) and modulates antioxidant defense enzymes (SOD, APX, GPX, CAT, GR and GST). The study reveals that exogenous Si application acts as a potent stress -modulating agent either via the formation of aluminum -silicate complexes or by improving the efficiency of antioxidant enzymatic activities in Al -contaminated soils. (c) 2024 SAAB. Published by Elsevier B.V. All rights reserved.

High bicarbonate concentration in the soil induces iron (Fe) deficiency in fruit trees. According to the promising performance of nanomaterials in supplying mineral nutrients, in this study the potential of 4 green synthesized Fe nano-complexes (Fe-NCs) on alleviating bicarbonate stress in almond trees was evaluated in a soilless culture. The Fe-NCs were formed on extracts of husks of almond, pistachio, walnut, and pomegranate and their efficiency in Fe supply was compared to a commercial FeEDDHA fertilizer. The bicarbonate stress was imposed by adding sodium bicarbonate + calcium carbonate to the Hoagland's nutrient solution: Control (without sodium bicarbonate + calcium carbonate); 10 mM NaHCO3+5 mM CaCO3; 20 mM NaHCO3+10 mM CaCO3. The plants were irrigated with nutrient solutions containing different concentrations of bicarbonate and different sources of Fe for 120 days. Bicarbonate stress induced chlorophyll decline, proline accumulation and leaf necrosis, and decreased leaf area. These responses were in line with decline in Fe concentration and development of oxidative damage in leaves, as hydrogen peroxide accumulation and membrane stability index decline were observed in the bicarbonatestressed plants. Although walnut-nFe and pistachio-nFe intensified these adverse effects of bicarbonate stress, the almond-nFe and pomegranate-nFe recovered chlorophyll concentration, alleviated the oxidative damage, and restored Fe in the plants to the range of FeEDDHA under bicarbonate stress. Alleviating the damages was related to retrieving the concentration of proteins, hydrogen peroxide detoxification, and catalase activity in the leaves. These findings uncovered the potential of green synthesized almond-nFe and pomegranate-nFe as low-cost and effective Fe sources under bicarbonate stress.

Soils with subsurface drip irrigation are often characterized by hypoxia, which could impair the aerobic respiration of roots and the productive potential of crops. Irrigation with hydrogen peroxide oxygenated water (HPOW) is one way to improve soil aeration in the rhizosphere. However, few studies have focused on exploring the interaction of HPOW with soil aeration and productivity of crops. The current work aimed to investigate the effects of four levels of HPOW [0 ppm H2O2 solution (tap water) as a control (H0), 600 ppm, 800 ppm and 1000 ppm H2O2 solution (H600, H800 and H1000)] on irrigation water properties, soil aeration, antioxidant defenses, growth biomarkers and yield components in winter wheat (Triticum aestivum L.) plants. Results confirmed that dissolved oxygen (DO) concentrations in H600, H800 and H1000 were significantly increased by 52.10%-126.59% and surface tension coefficients were significantly decreased by 17.72%-31.60% as compared to H0. DO concentrations in soil solutions irrigated with H600, H800 and H1000 were significantly elevated by 9.78%-15.68% as compared to H0, and the maximum value equal to 7.44 mg L-1 was found at a soil depth of 20 cm. Further, H600 and H800 reduced concentrations of malondialdehyde and H2O2 in leaves, increased accumulation of proline and activities of antioxidant enzymes, and resulted in an enhancement in grain yield of 15.28% and 25.23%, respectively. Application of H1000 resulted in lower growth biomarkers and yield components due to oxidative stress induced by decreased activities of antioxidant enzymes and accumulation of proline as well as elevated levels of lipid peroxidation as compared to H600 and H800. The optimal regulation was achieved with the H800 treatment. Overall, HPOW improved the plants growth by modulating soil aeration and antioxidant defenses which enhanced tolerance to hypoxic stress.