Nitric oxide and brassinosteroids enhance chromium stress tolerance in Glycine max L. (Merr.) by modulating antioxidative defense and glyoxalase systems

Alleviating lanthanum stress in tomato plants using MnO nanoparticles and triacontanol: Impacts on growth, photosynthesis, and antioxidant defense

The present study evaluated the synthesis, characterization, and ameliorative potential of manganese oxide nanoparticles (MnO NPs) against lanthanum (La)-induced stress in tomato plants. Biosynthesized MnO NPs exhibited a characteristic UV-Vis absorption peak at 276 nm and a cubic crystalline structure with an average crystallite size of 13 nm, as determined by XRD. TEM images confirmed pseudo-spherical morphology and homogenous distribution. Under La stress, tomato plants showed a significant reduction in shoot length (54.90 %), root length (62.39 %), shoot dry weight (49.71 %), and root dry weight (37.17 %). Application of MnO NPs and triacontanol (TRIA) mitigated these effects, with combined treatments enhanced shoot and root lengths by 155.81 % and 216.66 %, respectively, and dry weights by 116.58 % (shoot) and 173.06 % (root). La stressed plants demonstrated decreased accumulation of La in roots and shoots by about 36.64 % and 32.21 %, respectively, upon synergistic application of MnO NPs and TRIA. La stress decreased photosynthetic pigments, including chlorophyll a (53.56 %), chlorophyll b (51.28 %), total chlorophyll (53.10 %), and carotenoids (26.36 %). Combined MnO NPs and TRIA treatment significantly increased these pigments by 110.23 %, 263.15 %, 142.27 %, and 266.66 %, respectively. Photosynthetic efficiency parameters, such as net photosynthetic rate, stomatal conductance, and transpiration rate, also improved by up to 74.44 %, 119.00 %, and 89.44 %, respectively, under combined treatments. Relative water content (RWC) decreased by 49.83 % under La stress but increased by 84.75 % following combined treatments. Osmolytes like proline and glycine betaine were elevated by 20.13 % and 38.47 %, respectively. Reactive oxygen species (ROS)-related markers, including H₂O₂, malondialdehyde, and electrolyte leakage, were significantly reduced by 58.14 %, 28.46 %, and 39.81 %, respectively, with MnO NPs and TRIA. Antioxidant enzyme activities were enhanced, with combined treatments elevating SOD (27.02 %), CAT (15.38 %), APX (90.37 %), and GR (90.38 %). Moreover, activities of DHAR and MDHAR, previously suppressed by La, increased by 91.64 % and 81.75 %, respectively. The findings highlight the synergistic role of MnO NPs and TRIA in alleviating La toxicity by enhancing growth, photosynthetic efficiency, antioxidant defense, and reducing ROS, offering a sustainable approach for crop improvement under metal stress conditions.

Phytochemical responses of camelina to brassinolide and boron foliar spray under irrigation regimes

The high level of boron in dryland and semi-arid soils is an important issue that strongly affects growing and developing crops, especially under drought stress. Meanwhile, brassinosteroid (BR) as a noval stress hormone can improve resistance to abiotic stress in plants. To explore the appropriate foliar application of boron (0.5 and 1 %) and 24-Epi-brassinolide (0.5 and 1 μM) and their combinations on camelina (Camelina sativa L.) under irrigation regimes a field experiment was conducted during 2018-2020 years. Irrigation regime consisted of well irrigation from emergence until the end of the growing season (WI0), withholding irrigation from flowering to siligue formation (WI1), and withholding irrigation from siligue formation to harvest (WI2)]. Our finding revealed that boron had a destructive effect on phytochemical parameters of camelina while application of brassinolide mitigated the boron impacts and improved the parameters. Results showed the highest increase in chlorophyll a (26.8 and 23.8 %) at B0.5 + BR0.5 treatments under WI1 and WI2 conditions, respectively. Application of BR (0.5 and 1 μM) and low level of B (B0.5 %) combination alleviated drought stress by improving osmolyte accumulation (proline) (5-9% increase), antioxidant enzymes, superoxide dismutase (SOD) (5.35-5.72 % increase), catalase (CAT) capacity (4.10 % increase) and secondary metabolites (total phenol and flavonoid) (6.78-10.26 % and 4.60-5.27 % increase). Further, malondealdehide (MDA) decreased (8.73 %) at BR and B combination and increased with a high level of B (B1%) application under-withholding irrigation. All of these results confirmed that BR and B synergistically (mainly B0.5 + BR0.5 and B0.5 + BR1) regulate the phytochemical properties response in the camelina plant to drought stress.

Seed priming with alpha-tocopherol alleviates microplastic stress in Brassica rapa through modulations in morphological, physiological and biochemical attributes

Microplastics (MPs) have been regarded as emerging pollutants globally, and understanding of the injurious impacts of MPs on food crops is still scarce. MPs toxicity can disrupt the growth and physic-chemical characteristics of turnip seedlings. Hence, sustainable remediation techniques by employing growth regulators can alleviate harmful impacts and confer MPs tolerance in vegetables. It was aimed to explore the impact of α-tocopherol for the alleviation of MPs toxicity in Brassica rapa seedlings. During present investigation, seed priming was executed with 25, 50 and 100 mg L-1α-tocopherol and then concerned soaked seeds of B. rapa were grown in Perti dishes treated with MPs (50 mg L-1). The current study showed that MPs toxicity significantly reduced seed germination, growth attributes, and photosynthetic activity while remarkably boosting the level of enzymatic and non-enzymatic antioxidants. Nevertheless, seed priming with α-tocopherol mitigated the MPs stress in Brassica rapa by augmenting growth attributes, photosynthetic machinery, phenol, flavonoid, proline and antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Furthermore, α-tocopherol supply meaningfully lowered the malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents of B. rapa under MPs stressed conditions. Hence, seed priming with α-tocopherol can be a promising strategy for promoting turnip crop production in MPs-contaminated environments. These outcomes will offer new insights into the sustainable management of the harmful effects of MPs on food crops.

Deciphering the role of nitric oxide in mitigation of systemic fungicide induced growth inhibition and oxidative damage in wheat

Consento (CON) poses a significant environmental hazard as a systemic fungicide, adversely affecting the health of non-target organisms. Nitric oxide (NO), a signaling molecule, is known to play a crucial role in plant physiology and abiotic stress tolerance. However, whether NO plays any role to enhance fungicide CON tolerance in wheat seedlings is yet unclear. Therefore, we conducted a hydroponic experiment i) to investigate the morpho-physio-biochemical changes of wheat seedlings to fungicide CON stress, and ii) to examine the effects of NO and fungicide CON treatments on oxidative damage, antioxidant system, secondary metabolism and detoxification of systemic fungicide in wheat seedlings. The results showed that CON fungicide at the highest (4X) concentration significantly decreased wheat seedlings fresh weight (46.89%), shoot length (40.26%), root length (56.11%) and total chlorophyll contents (67.44%) in a dose response relationship. Moreover, CON significantly increased hydrogen peroxide, malondialdehyde, catalase, ascorbate peroxidase, glutathione-S-transferase, and peroxidase activities while decreased reduced glutathione (GSH) content. This ultimately impaired the redox homeostasis of cells, leading to oxidative damage in cell membrane. Under fungicide treatment, the addition of NO reduced the fungicide phytotoxicity, with an increase of over 60% in seedling growth. The NO application mitigated CON phytotoxicity as reflected by significantly increased chlorophyll pigments (69.88%) and decreased oxidative damage in wheat leaves. Indeed, the NO alleviatory effect was able to increase the tolerance of seedlings to fungicide, which resulted increments in antioxidant and detoxification enzymes activity, with the enhanced GSH level (78.54%). Interestingly, NO alleviated CON phytotoxicity through the phenylpropanoid pathway by enhancing the activity of secondary metabolism enzymes such as phenylalanine ammonia-lyase (47.28%), polyphenol oxidase (9%), and associated metabolites such as phenolic acids (77.62%), flavonoids (34.33%) in wheat leaves. Our study has provided evidence that NO plays a key role in the metabolism and detoxification of systemic fungicide in wheat through enhanced activity of antioxidants, detoxifications and secondary metabolic enzymes.

Surface modified ZnO NPs by betaine and proline build up tomato plants against drought stress and increase fruit nutritional quality

Drought stress is a serious challenge for global food production. Nanofertilizers and nanocomposites cope with such environmental stresses and also increase nutritional contents of fruits. An in vitro experiment was designed to use Zinc Oxide Nanoparticles (ZnO NPs) primed with Proline and Betaine (ZnOP and ZnOBt NPs) at 50 and 100 mg/kg soil against drought stress in Tomato (Solanum lycopersicum) plants. Plant morphological, biochemical, and fruit nutritional quality were accessed. Maximum plant height was observed under the treatment of ZnOP50 (1.09 m) and ZnO 100 (1.06 m). ZnOP and ZnOBt also improved the chlorophyll content up to 86% and 87.16%, respectively. Application of ZnOP NPs also demonstrated maximum tomato yield (204 g tomato/plant) followed by ZnO NPs and ZnOBt NPs. Nanocomposites decreased phenolics and flavonoids contents in drought stressed plants demonstrating the mitigation of oxidative stress. Nanofertilizer also increased the concentration of phenolics and flavonoids in fruits that increased the nutritional contents. Furthermore a significant accumulation of betaine, proline, and lycopene in fruits on nanocomposite treatment made it nutritional and healthy. Lycopene content increased up to 2.01% and 1.23% in presence of ZnOP50 and ZnOP100, respectively. These outcomes validate that drought stress in plant can be reduced by accumulation of different phytochemicals and quenching oxidative stress. The study deems that nano zinc carrying osmoregulators can greatly reduce the negative effects of drought stress and increase nutritional quality of tomato fruits.

Phytohormones and related genes function as physiological and molecular switches regulating water stress response in the sunflower

Water deficit stress reduces crop yield in field crops, including sunflowers, at any growth stage. In response, most plants activate hormonal and gene expression patterns to mitigate damage. In this study, we evaluated changes in the physiological and gene transcription levels of two sunflower (Helianthus annuus L.) inbred lines -one sensitive (B59 line) and one water stress-tolerant (B71)-in response to water stress, by using mannitol to simulate water deficit conditions, which provides moderate stress in both sunflower lines. The analyses of the accumulation of various phytohormones under this stress revealed that Jasmonic acid (JA) significantly increased in the shoots of both lines. Similarly, Salicylic acid (SA) increased in the shoots of both lines, although it also accumulated in B71 roots. In addition, Abscisic acid (ABA) and Indole-3-acetic acid (IAA) showed a considerable increase in the B59 shoots. Regarding the JA and SA pathways, the WRKY70 transcription levels were higher in the shoots of both lines and the roots of B71. The B59 line showed overtranscription of a gene related to the ABA pathway (XERICO) and genes associated with IAA (ARF9 and ARF16 genes). The B71 line, on the other hand, simultaneously triggered the JA, SA and ABA hormonal pathways in response to this stress condition. The ABA and JA hormonal pathways activated different TFs, such as RD20, RD22, RD26, ANAC19 and ANAC29, through MYC2. Both the JA and SA hormonal pathways activated the WRKY70 transcription factor. Altogether, each line triggered the hormonal and transcriptional pathways in response to water stress, although at varying intensities. The results suggest that the hormonal pathways of JA, SA, IAA and ABA, along with their primary associated genes, are activated in response to water deficit at the early growth stage in sunflower seedlings, which mitigates damage.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01497-8.

24-epibrassinolide as a multidimensional regulator of rice (Oryza sativa) physiological and molecular responses under isoproturon stress

Brassinosteroids (BRs) can regulate various processes in plant development and defense against environmental stress. In this study, the contribution of BRs in the degradation of isoproturon (IPU) in rice has been established. IPU has a significant effect on rice growth, chlorophyll content, and membrane permeability. When treated with 1.0 μmol/L 24-epibrassinolide (EBR), a BR analogue, the associated symptoms of rice poisoning were alleviated as the IPU levels in the rice and growth media were decreased. In the presence of EBR, the activities of several IPU-related detoxification enzymes were enhanced to cope with the stress due to IPU. An RNA-sequencing (RNA-Seq) has been performed to determine the variation of transcriptomes and metabolic mechanisms in rice treated with EBR, IPU, or IPU+EBR. Some of the differentially expressed genes (DEGs) were Phase I-III reaction components of plants, such as cytochrome P450 (CYP450), glutathione S-transferase (GST), glycosyltransferases (GTs), and the ATP-binding cassette transporter (ABC transporter). The expression of some signal transduction genes was significantly up-regulated. The relative content of low-toxicity IPU metabolites increased due to the presence of EBR as determined by UPLC/Q-TOF-MS/MS. The IPU metabolic pathways include enzyme-catalyzed demethylation, hydroxylation, hydrolysis, glycosylation, and amino acid conjugation processes. The results suggest that EBR plays a key role in the degradation and detoxification of IPU. This study has provided evidence that BRs regulate the metabolism and detoxification of IPU in rice, and offers a new approach to ensuring cleaner crops by eliminating pesticide residues in the environment.

Role of methylglyoxal and glyoxalase in the regulation of plant response to heavy metal stress

KEY MESSAGE

Methylglyoxal and glyoxalase function a significant role in plant response to heavy metal stress. We update and discuss the most recent developments of methylglyoxal and glyoxalase in regulating plant response to heavy metal stress. Methylglyoxal (MG), a by-product of several metabolic processes, is created by both enzymatic and non-enzymatic mechanisms. It plays an important role in plant growth and development, signal transduction, and response to heavy metal stress (HMS). Changes in MG content and glyoxalase (GLY) activity under HMS imply that they may be potential biomarkers of plant stress resistance. In this review, we summarize recent advances in research on the mechanisms of MG and GLY in the regulation of plant responses to HMS. It has been discovered that appropriate concentrations of MG assist plants in maintaining a balance between growth and development and survival defense, therefore shielding them from heavy metal harm. MG and GLY regulate plant physiological processes by remodeling cellular redox homeostasis, regulating stomatal movement, and crosstalking with other signaling molecules (including abscisic acid, gibberellic acid, jasmonic acid, cytokinin, salicylic acid, melatonin, ethylene, hydrogen sulfide, and nitric oxide). We also discuss the involvement of MG and GLY in the regulation of plant responses to HMS at the transcriptional, translational, and metabolic levels. Lastly, considering the current state of research, we present a perspective on the future direction of MG research to elucidate the MG anti-stress mechanism and offer a theoretical foundation and useful advice for the remediation of heavy metal-contaminated environments in the future.

Mitigating chromium toxicity in rice (Oryza sativa L.) via ABA and 6-BAP: Unveiling synergistic benefits on morphophysiological traits and ASA-GSH cycle

In recent years, the use of plant hormones, such as abscisic acid (ABA) and 6-benzylaminopurine (6-BAP), has gained significant attention for their role in mitigating abiotic stresses across various plant species. These hormones have been shown to play a vital role in enhancing the ascorbate-glutathione cycle and eliciting a wide range of plant growth and biomass, photosynthetic efficiency, oxidative stress and response of antioxidants and other physiological responses. While previous research has been conducted on the individual impact of ABA and 6-BAP in metal stress resistance among various crop species, their combined effects in the context of heavy metal-stressed conditions remain underexplored. The current investigation is to assess the beneficial effects of single and combined ABA (5 and 10 μM L-1) and 6-BAP (5 and 10 μM L-1) applications in rice (Oryza sativa L.) cultivated in chromium (Cr)-contaminated soil (100 μM). Our results showed that the Cr toxicity in the soil showed a significant declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in O. sativa. However, Cr toxicity significantly increased oxidative stress biomarkers, organic acids, enzymatic and non-enzymatic antioxidants including their gene expression in O. sativa seedlings. Although, the application of ABA and 6-BAP showed a significant increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, And Cr uptake. In addition, individual or combined application of ABA and 6-BAP enhanced the cellular fractionation and decreases the proline metabolism and AsA-GSH cycle in rice plants. 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.

Role of Acetic Acid and Nitric Oxide against Salinity and Lithium Stress in Canola (Brassica napus L.)

In this study, canola (Brassica napus L.) seedlings were treated with individual and combined salinity and lithium (Li) stress, with and without acetic acid (AA) or nitric acid (NO), to investigate their possible roles against these stresses. Salinity intensified Li-induced damage, and the principal component analysis revealed that this was primarily driven by increased oxidative stress, deregulation of sodium and potassium accumulation, and an imbalance in tissue water content. However, pretreatment with AA and NO prompted growth, re-established sodium and potassium homeostasis, and enhanced the defense system against oxidative and nitrosative damage by triggering the antioxidant capacity. Combined stress negatively impacted phenylalanine ammonia lyase activity, affecting flavonoids, carotenoids, and anthocyanin levels, which were then restored in canola plants primed with AA and NO. Additionally, AA and NO helped to maintain osmotic balance by increasing trehalose and proline levels and upregulating signaling molecules such as hydrogen sulfide, γ-aminobutyric acid, and salicylic acid. Both AA and NO improved Li detoxification by increasing phytochelatins and metallothioneins, and reducing glutathione contents. Comparatively, AA exerted more effective protection against the detrimental effects of combined stress than NO. Our findings offer novel perspectives on the impacts of combining salt and Li stress.

Effect of seed priming by taurine on growth and chromium (Cr) uptake in canola (Brassica napus L.) under Cr stress

Taurine is a recently recognized plant growth regulator under abiotic stress. However, the information on taurine-mediated plant defense responses is scarce, particularly on taurine-mediated regulation of the glyoxalase system. There is currently no report available on the use of taurine as seed priming under stress. Chromium (Cr) toxicity considerably subsided growth characteristics, photosynthetic pigments, and relative water content. Furthermore, plants encountered intensified oxidative injury due to a significant increase in relative membrane permeability, H2O2, O2•‒, and MDA production. The amount of antioxidant compounds and the functioning of antioxidant enzymes rose, but imbalance due to over ROS generation frequently depleted antioxidant compounds. Taurine seed priming (50, 100, 150, and 200 mg L‒1) notably diminished oxidative injury, strengthened the antioxidant system, and conspicuously subsided methylglyoxal levels through enhanced activities of glyoxalase enzymes. The accumulation of Cr content was minimal in plants administered taurine as seed priming. In conclusion, our research demonstrates that taurine priming effectively mitigated the adverse effects of Cr toxicity on canola. Taurine reduced oxidative damage, leading to improved growth, enhanced chlorophyll levels, optimized ROS metabolism, and enhanced methylglyoxal detoxification. These findings highlight the potential of taurine as a promising strategy to enhance the tolerance of canola plants to Cr toxicity.

Methyl jasmonate and selenium synergistically mitigative cadmium toxicity in hot pepper (Capsicum annuum L.) plants by improving antioxidase activities and reducing Cd accumulation

Methyl jasmonate (MeJA) or selenium (Se)-mediated response to cadmium (Cd) stress in plant has been widely reported, but the combined effects both on plant growth in response to Cd stress and the underlying mechanisms remain obscure. Here, we showed the combined effects of MeJA (2.5 μM) and Se (7 μM) on hot pepper growth under Cd stress (CdCl2, 5 μM). The results showed Cd suppressed the accumulation of total chlorophyll and carotenoid and reduced the photosynthesis, while it increased the content of endogenous signaling molecules, e.g. nitric oxide (NO) and hydrogen peroxide (H2O2), as well as Cd content in leaves. The combined application of MeJA and Se significantly decreased the malondialdehyde (MDA) accumulation and improved the activities of antioxidant enzymes (AOEs, e.g. SOD and CAT) and defense-related enzymes (DREs, POD and PAL). Additionally, the synergistic application of MeJA and Se also obviously improved photosynthesis in hot pepper plants under Cd stress compared with those treated with MeJA or Se respectively or not. Moreover, the treatment of MeJA associated with Se also effectively reduced the Cd accumulation in hot pepper leaves under Cd stress compared with the plants treated with MeJA or Se separately, which implied a potentially synergistic role of MeJA and Se in alleviating Cd toxicity in hot pepper plants. This study provides a theoretical reference for the further analysis of the molecular mechanism of MeJA and Se in jointly mediating the response to heavy metals in plants.