The molecular paradigm of reactive oxygen species (ROS) and reactive nitrogen species (RNS) with different phytohormone signaling pathways during drought stress in plants

Development of a near-infrared fluorescent probe for in situ monitoring of hydrogen peroxide in plants

In plants, hydrogen peroxide (H2O2), one of the significant reactive oxygen species, plays a dual function. Investigating its concentration is essential for understanding its production and scavenging mechanisms in plants. In this study, a near-infrared fluorescent probe (Cy-Bo) was developed, which is based on the hemicyanine compound. By introducing indole salts into the oxygenated anthraquinone structure, the conjugated system is expanded, enabling the probe to emit long-wavelength fluorescence in the near-infrared region, thereby minimizing interference from other biomolecules in plant tissues (λex = 650 nm, λem = 720 nm). As for the specific recognition of H2O2, the pinacol phenylborate ester was selected to be the recognition group. It shows good linearity (R2 = 0.998) in the concentration range of 0.5-100 μM, with a detection limit of 0.07 μM. Furthermore, this probe Cy-Bo has been used for in vivo fluorescence imaging in plants due to its good bio-penetration and in-situ imaging capabilities. The results reveal a significant increase in H2O2 concentration in Arabidopsis thaliana under progressively increasing drought, high-temperature, and salt stress. This tool provides a non-invasive, in situ imaging method for detecting H2O2 in plants, which has a fast response, easy operation, and high sensitivity. It enables visual monitoring of H2O2 fluctuations and aids in advancing physiological and pathological studies related to H2O2.

Nitric oxide stimulates digestion modifying the nutrient composition of the traps' fluid of Nepenthes x ventrata

External digestion performed by autotrophs is a characteristic feature of carnivorous plants, such as those of the Nepenthes spp. These plants developed jug-shaped traps filled with digestive fluid that consists of water, various proteins (mostly enzymes), and nutrients. Moreover, the presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the traps' fluid of N. ventrata has been demonstrated. RNS, among them nitric oxide (NO), accelerates digestion e.g. by the alteration of ROS levels. The aim of the study was to demonstrate the stimulation of external digestion by NOx supplementation linked to the modulation of the nutrient composition of the trap fluid, digestive enzyme activity and gene transcription. Using the digestion fluid of N. ventrata mature traps we indicated that NOx temporarily increases K, Fe, Cu and ammonia that may be involved in the modulation of free radicals content. The stimulatory effect of NOx on the activities of enzymes responsible for digestion, and on the transcripts' levels of Nepenthesin I and II, Purple Acid Phosphatase, and S-like Ribonuclease was shown. The decrease in the level of carbonylated proteins (from food source) in the trap' fluid during digestion suggests their absorption by Nepenthes trap tissues. We also demonstrated the presence of carbonylated proteins in the trap fluid before feeding.

An activatable near-infrared probe for in situ monitoring of hydrogen peroxide in plant tissues

Biotic and abiotic stresses can disrupt plant metabolic processes. This leads to the excessive accumulation of hydrogen peroxide (H2O2) in plants, which in turn induces oxidative stress. Therefore, detection of H2O2 is critical to understanding plant growth. In this study, we developed a naphthalene-based fluorescein near-infrared fluorescent probe (NAPF-AC) for the sensitive and selective detection of H2O2. Upon exposure to H2O2, the probe undergoes disruption of its push-pull electronic structure, triggering an intramolecular charge transfer process that allows for fluorescence-based detection. NAPF-AC exhibited excellent linearity (R2 = 0.998) over a wide concentration range of H2O2 (0.1 to 100 μM), with a limit of detection (LOD) as low as 0.05 μM. In addition, NAPF-AC was successfully used for the in-situ detection of H2O2 in plant tissues. This study provides a powerful tool for studying H2O2 dynamics in plants and offers new insights into the mechanisms regulating plant growth and stress responses.

Functional analysis of open stomata 1-slow anion channel associated 1-6 protein module in enhancing drought tolerance in tomato through stomatal regulation mechanisms

Tomato (Solanum lycopersicum) is an important vegetable crop, whose growth and development are frequently subjected to drought stress, which severely limits its growth and yield. Identifying key drought-resistance genes in tomato is crucial for elucidating the mechanisms of drought resistance and improving tomato's drought tolerance, which has practical implications for agricultural production. The results of this study demonstrate that silencing SlSLAC1-6 (Slow anion channel associated 1-6) reduces tomato's drought tolerance. SnRK2.6/OST1 (Open stomata 1) protein kinase is a key component in plants' resistance to abiotic stress. Interactions between SlOST1 and SlSLAC1-6 were confirmed through Y2H, BiFC, LCI, Co-IP, and Pull-down assays. Simultaneously, overexpression and knockout of SlOST1 proved that it positively regulates tomato's drought tolerance by influencing reactive oxygen species (ROS) homeostasis, photosynthetic capacity, stomatal closure, and other mechanisms. Silencing SlSLAC1-6 in SlOST1 knockout plants further reduced tomato's drought tolerance. The regulation of tomato drought tolerance by SlOST1 and SlSLAC1-6 highlights the complexity of plant adaptation to drought. These findings provide new insights into the regulatory network of the SlOST1-SlSLAC1 protein module in tomato drought tolerance and offer gene resources for future tomato drought-resistance breeding.

Antifungal effect and control of Alternaria fruit rot in blueberry through ε-polylysine hydrochloride

Blueberry was easily infected by Alternaria sp. during storage time, leading to Alternaria fruit rot (AFR). ε-polylysine hydrochloride (ε-PL), a widely used food additive, was evaluated for its antifungal efficacy at different concentrations and its effects on the quality of blueberries treated with 3 g L-1 ε-PL. The results revealed that ε-PL effectively inhibited the mycelial growth of Alternaria sp. by destroying its cell membrane structure, resulting in nucleic acid and soluble protein leakage. Furthermore, ε-PL treatment reduced the incidence of AFR in blueberries by 23.7 % at 4 d. It enhanced the disease resistance of blueberries by increasing both the activity and gene expression of β-1,3-glucanase. Additionally, ε-PL elevated the activities and gene expression of antioxidant enzymes, thereby reducing hydrogen peroxide content by 62.77 %. These findings suggested that ε-PL could serve as a novel antifungal agent for managing postharvest AFR in blueberries.

Physiological and molecular mechanisms of nitrogen in alleviating drought stress in Phoebe bournei

To explore the mechanisms by which nitrogen alleviates drought stress in Phoebe bournei, this study integrated drought treatment with exogenous nitrogen application to assess physiological characteristics and employed transcriptome sequencing to decipher transcriptional responses. The results indicated that nitrogen fertilizer mitigated leaf wilting in P. bournei under drought stress and significantly enhanced leaf dry weight, fresh weight, thickness, and chlorophyll content. Furthermore, nitrogen improved photosynthesis by inhibiting stomatal closure, enhancing light energy absorption, and accelerating electron transport in PSII. 11 photosynthesis-related genes, including PFP, TRY, LQY, FTSH, FRO, CURT, PETF, ATPF, PETA, CRRSP, and MEN and 17 carbohydrate metabolism-associated genes, such as PWD, GBE1, GAPA, PFKA, RFS, ISA, GLGC, PGK, ALDO, GUX, RX9, MIOX, HCT, BAM, MPFP, and ERNI exhibited differential expression in response to nitrogen. Moreover, nitrogen treatment significantly modulated plant hormone metabolism, with 44 upregulated and 14 downregulated differentially expressed genes (DEGs) primarily associated with jasmonic acid (JA) synthesis and signaling. These findings provide new insights into enhancing the drought tolerance of P. bournei in the context of global climate change.

Unlocking the Synergy: ABA Seed Priming Enhances Drought Tolerance in Seedlings of Sweet Sorghum Through ABA-IAA Crosstalk

Abscisic acid (ABA) seed priming impacts plant growth and stress resistance, yet its precise physiological and molecular mechanisms remain elusive. This study explored the role of ABA-priming in enhancing drought acclimation in sweet sorghum (Sorghum bicolor Moench) using physiological assessments and comparative transcriptomics. Under drought stress, ABA-primed seedlings exhibited increased plant height, larger leaves, and higher leaf water content compared to non-primed plants. While drought negatively affected photosynthesis through the regulation of photosystem I and II, ABA-priming improved photosynthesis and WUE by involving in differential expression of photosystem II genes. ABA-priming promoted the accumulation of cuticular wax and cutin, effectively reducing leaf water loss. Drought triggered endogenous ABA production via ABA inactivation genes (UGT, BGLU), while ABA-priming activated auxin (IAA) biosynthesis via YUCCA, enhancing auxin-mediated responses and gibberellic acid (GA) signalling. The synergistic action of ABA and IAA culminated in enhanced drought tolerance. Additionally, ABA-priming and drought stress regulated NAC transcription factors, with SbNAC21-1 emerging as a pivotal transcriptional activator intricately linked to auxin signalling. Overexpression of SbNAC21-1 in Arabidopsis effectively enhanced drought tolerance. These findings offer valuable insights into the intricate mechanisms underpinning the beneficial effects of ABA-priming, ultimately enhancing plant adaptability to environmental stressors.

Hormesis effect of cadmium on pakchoi growth: Unraveling the ROS-mediated IAA-sugar metabolism from multi-omics perspective

Previous research on cadmium (Cd) focused on toxicity, neglecting hormesis and its mechanisms. In this study, pakchoi seedlings exposed to varying soil Cd concentrations (CK, 5, 10, 20, 40 mg/kg) showed an inverted U-shaped growth trend (hormesis characteristics): As Cd concentration increases, biomass exhibited hormesis character (Cd5) and then disappear (Cd40). ROS levels rose in both Cd treatments, with Cd5 being intermediate between CK and Cd40. But Cd5 preserved cellular structure, unlike damaged Cd40, hinting ROS in Cd5 acted as signaling regulators. To clarify ROS controlled subsequent metabolic processes, a multi-omics study was conducted. The results revealed 143 DEGs and 793 DEMs across all Cd treatment. KEGG indicated among all Cd treatments, the functional differences encompass: "plant hormone signal transduction" and "starch and sucrose metabolism". Through further analysis, we found that under the influence of ROS, the expression of IAA synthesis and signaling-related genes was significantly up-regulated, especially under Cd5 treatment. This further facilitated the accumulation of reducing sugars, which provided more energy for plant growth. Our research results demonstrated the signaling pathway involving ROS-IAA-Sugar metabolism, thereby providing a novel theoretical basis for cultivating more heavy metal hyperaccumulator crops and achieving phytoremediation of contaminated soils.

Enhancing domestic wastewater treatment through four chlorophyta strains-based phycoremediation: nutrient removal efficiency and algal physiology

Phycoremediation is a promising solution for environmentally sustainable wastewater treatment. However, its effectiveness depends on the selection of suitable microalgae species. In this study, four algal species (Chlorella sorokiniana, Chlorella vulgaris, Scenedesmus ecornis, and Strombomonas sp.) were evaluated for their ability to remove pollutants from secondary treated domestic wastewater using multi-soil-layering (MSL) technology. Among the four strains tested, Chlorella sorokiniana exhibited the highest algal density (2.832 ± 0.187 × 107 cells/mL) and outperformed other species with phosphorus, nitrogen, and COD removal rates exceeding 82.01%, 63.64%, and 61.09% respectively. In addition, Chlorella sorokiniana had a higher total chlorophyll content of 31.11 µg. L-1 (Chl a: 15.47 ± 0.148 µg. L-1; Chl b: 15.642 ± 0.052 µg. L-1) than other species. Physiological analyses of proline and glycine betaine indicated that the two Chlorella strains experienced lower stress levels, which facilitated an accelerated bioremediation process compared to other Chlorophyta, namely Scenedesmus ecornis and Strombomonas sp. The efficiency of C. sorokiniana in the treatment of secondary treated wastewater from MSL, combined with its maximum biomass production, underlines its potential for industrial application. Consequently, there is a compelling interest in evaluating C. sorokiniana within a prototype as a prelude to industrial development.

Functional Characterization of β-Glucuronidase Genes Involved in Baicalein Biosynthesis from Scutellaria baicalensis Based on Transcriptome Analysis

Baicalein is a unique flavonoid compound with important pharmacological activities, derived from Scutellaria baicalensis Georgi. Baicalein, as the aglycone of baicalin, is a key form for exerting pharmacological activity in vivo. β-glucuronidases (GUSs) are the enzymes involved in the conversion of baicalin to baicalein. In this study, the content of baicalein in S. baicalensis was significantly increased by 20.44% after treatment with 5% PEG6000. Seven GUSs from the glycoside hydrolase 79 family were identified through comparative transcriptome analysis. Among them, GUS1 and GUS2 were confirmed to have catalytic activity in converting baicalin to baicalein in prokaryotic and eukaryotic systems. The correlation analysis further revealed a significant positive correlation of 0.962 (p < 0.01) between the expression of GUS2 and baicalein content in six different sources of S. baicalensis. Interestingly, the presence of variable sites in the GUS1 and GUS2 genes significantly affected their catalytic efficiency in the S. baicalensis samples from the six geographic origins. These findings also provide valuable GUS biological enzyme resources for the effective synthesis of baicalein and offer new insights into the accumulation pattern of baicalein in S. baicalensis.

Dressed Up to the Nines: The Interplay of Phytohormones Signaling and Redox Metabolism During Plant Response to Drought

Plants must effectively respond to various environmental stimuli to achieve optimal growth. This is especially relevant in the context of climate change, where drought emerges as a major factor globally impacting crops and limiting overall yield potential. Throughout evolution, plants have developed adaptative strategies for environmental stimuli, with plant hormones and reactive oxygen species (ROS) playing essential roles in their development. Hormonal signaling and the maintenance of ROS homeostasis are interconnected, playing indispensable roles in growth, development, and stress responses and orchestrating diverse molecular responses during environmental adversities. Nine principal classes of phytohormones have been categorized: auxins, brassinosteroids, cytokinins, and gibberellins primarily oversee developmental growth regulation, while abscisic acid, ethylene, jasmonic acid, salicylic acid, and strigolactones are the main orchestrators of environmental stress responses. Coordination between phytohormones and transcriptional regulation is crucial for effective plant responses, especially in drought stress. Understanding the interplay of ROS and phytohormones is pivotal for elucidating the molecular mechanisms involved in plant stress responses. This review provides an overview of the intricate relationship between ROS, redox metabolism, and the nine different phytohormones signaling in plants, shedding light on potential strategies for enhancing drought tolerance for sustainable crop production.

Bacillus cereus: An Ally Against Drought in Popcorn Cultivation

Despite the development of adapted popcorn cultivars such as UENF WS01, strategies such as bacterial inoculation are being explored to enhance plant resilience to abiotic stress. This study investigates the impact of drought stress on popcorn cultivation. Specifically, the aim was to identify the benefits of Bacillus cereus interaction with the drought-tolerant hybrid UENF WS01 for its morphophysiology and growth by comparing inoculated and non-inoculated plants under water-stressed (WS) and well-watered (WW) conditions. This evaluation was conducted using a randomized complete block design in a factorial arrangement. For WS with inoculation samples, there were significant increases in relative chlorophyll content, maximum fluorescence intensity, and agronomic water use efficiency. Chlorophyll content increased by an average of 50.39% for WS samples, compared to a modest increase of 2.40% for WW samples. Both leaf and stem biomass also significantly increased for WS relative to WW conditions. Overall, B. cereus inoculation mitigated the impact of water stress, significantly enhancing the expression of physiological and morphological traits, even when paired with a drought-tolerant hybrid.

Genome-wide identification of hormone biosynthetic and metabolism genes in the 2OGD family of tobacco and JOX genes silencing enhances drought tolerance in plants

Phytohormones play crucial roles in regulation of plant growth and tolerance to abiotic stresses. The 2-oxoglutarate-dependent dioxygenase (2OGD) superfamily responds to hormone biosynthesis and metabolism in plants. However, the Nt2OGD family in tobacco has not been fully explored. In this study, we identify 126 members of the Nt2OGD family, and 60 of them are involved in hormone biosynthesis and metabolism process (Nt2OGD-Hs), including 1-aminocyclopropane-1-carboxylic acid oxidases (ACO), dioxygenases for auxin oxidation (DAO), gibberellin (GA) 20-oxidases and 3-oxidases (GA20ox and GA3ox), carbon-19 and carbon-20 GA 2-oxidases (C19-GA2ox and C20-GA2ox), lateral branching oxidoreductases (LBO), jasmonate-induced oxygenases (JOX), downy mildew resistant 6, and DMR6-like oxygenases (DMR6/DLO). Gene duplication analysis suggests the segmental duplication and whole genome duplication (WGD) might be a potential mechanism for the expansion of this family. Expression analysis reveals that most of Nt2OGD-Hs show tissue-specific expression patterns, and some of them respond to environmental conditions. Of Nt2OGD-Hs, the expression of NtJOX3 and NtJOX5, which are involved in JA metabolism, exhibits remarkable changes during drought treatments. Silencing of NtJOX3 or NtJOX5 increases tobacco tolerance to drought stress. Furthermore, knocking out OsJOX3 and OsJOX4, respectively in rice, result in high tolerance to drought. Taken together, our work comprehensively identifies the Nt2OGD family in tobacco and provides new insights into roles of the JA pathway in drought tolerance in plants.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

The Interplay of Nitric Oxide and Nitrosative Modifications in Maize: Implications for Aphid Herbivory and Drought Stress

Nitric oxide (NO) and other reactive nitrogen species (RNS) are considered to be signaling molecules in higher plants involved in the regulation of growth and development processes. However, the molecular mechanisms of their formation, removal, and participation in plant responses to adverse environmental stimuli remain largely unclear. Therefore, the aim of this study was to assess the influence of selected single stresses and combined stresses (i.e., Rhopalosiphum padi L. aphid infestation, drought, aphid infestation, and drought) and post-stress recovery on the contents of NO and peroxynitrite anion (ONOO-), as well as the levels of mRNA and protein nitration (i.e., the 8-nitroguanine and protein 3-nitrotyrosine amounts, respectively), in maize seedlings (Zea mays L.). Moreover, the expression patterns of the two tested genes (nos-ip, encoding nitric oxide synthase-interacting protein, and nr1, encoding nitrate reductase 1) involved in NO metabolism in maize plants were quantified. We identified significant intervarietal, time-course, and stress-dependent differences in the levels of the quantified parameters. Under the investigated stress conditions, the aphid-resistant Waza cv. seedlings were characterized by a higher and earlier NO accumulation and mRNA nitration level and an increased expression of the two target genes (nos-ip and nr1), compared to the aphid-susceptible Złota Karłowa cv. seedlings. Conversely, the Złota Karłowa plants responded with a greater elevation in the content of ONOO- and protein 3-nitrotyrosine than the Waza cv. plants The multifaceted role of NO and its derivatives in maize plants challenged by single and combined stresses, as well as during post-stress recovery, is discussed.

Functional Analysis of Cucumis melo CmXTH11 in Regulating Drought Stress Tolerance in Arabidopsis thaliana

The CmXTH11 gene, a member of the XTH (xyloglucan endotransglycosylase/hydrolase) family, plays a crucial role in plant responses to environmental stress. In this study, we heterologously expressed the melon gene CmXTH11 in Arabidopsis to generate overexpressing transgenic lines, thereby elucidating the regulatory role of CmXTH11 in water stress tolerance. Using these lines of CmXTH11 (OE1 and OE2) and wild-type (WT) Arabidopsis as experimental materials, we applied water stress treatments (including osmotic stress and soil drought) and rewatering treatments to investigate the response mechanisms of melon CmXTH11 in Arabidopsis under drought stress from a physiological and biochemical perspective. Overexpression of CmXTH11 significantly improved root growth under water stress conditions. The OE lines exhibited longer roots and a higher number of lateral roots compared to WT plants. The enhanced root system contributed to better water uptake and retention. Under osmotic and drought stress, the OE lines showed improved survival rates and less wilting compared to WT plants. Biochemical analyses revealed that CmXTH11 overexpression led to lower levels of malondialdehyde (MDA) and reduced electrolyte leakage, indicating decreased oxidative damage. The activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), were significantly higher in OE lines, suggesting enhanced oxidative stress tolerance. The CmXTH11 gene positively regulates water stress tolerance in Arabidopsis by enhancing root growth, improving water uptake, and reducing oxidative damage. Overexpression of CmXTH11 increases the activities of antioxidant enzymes, thereby mitigating oxidative stress and maintaining cellular integrity under water deficit conditions. These findings suggest that CmXTH11 is a potential candidate for genetic improvement of drought resistance in crops.

Effects of Drought Stress on Leaf Functional Traits and Biomass Characteristics of Atriplex canescens

Drought is a critical factor constraining plant growth in arid regions. However, the performance and adaptive mechanism of Atriplex canescens (A. canescens) under drought stress remain unclear. Hence, a three-year experiment with three drought gradients was performed in a common garden, and the leaf functional traits, biomass and biomass partitioning patterns of A. canescens were investigated. The results showed that drought stress had significant effects on A. canescens leaf functional traits. A. canescens maintained the content of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD), but the peroxidase (POD) and catalase (CAT) activity decreased, and the content of proline (Pro) and soluble sugar (SS) increased only under heavy drought stress. Under drought stress, the leaves became smaller but denser, the specific leaf area (SLA) decreased, but the dry matter content (LDMC) maintained stability. Total biomass decreased 60% to 1758 g under heavy drought stress and the seed and leaf biomass was only 10% and 20% of non-stress group, but there had no significant difference on root biomass. More biomass was allocated to root under drought stress. The root biomass allocation ratio was doubled from 9.62% to 19.81% under heavy drought, and the root/shoot ratio (R/S) increased from 0.11 to 0.25. The MDA was significantly and negatively correlated with biomass, while the SPAD was significantly and positively correlated with total and aboveground organs biomass. The POD, CAT, Pro and SS had significant correlations with root and seed allocation ratio. The leaf morphological traits related to leaf shape and weight had significant correlations with total and aboveground biomass and biomass allocation. Our study demonstrated that under drought stress, A. canescens made tradeoffs between growth potential and drought tolerance and evolved with a conservative strategy. These findings provide more information for an in-depth understanding of the adaption strategies of A. canescens to drought stress and provide potential guidance for planting and sustainable management of A. canescens in arid and semi-arid regions.

Mitigating Ni and Cu ecotoxicity in the ecological restoration material and ornamental Primula forbesii Franch. with exogenous 24-epibrassinolide and melatonin

Nickel (Ni) and copper (Cu) contamination have become major threats to plant survival worldwide. 24-epibrassinolide (24-EBR) and melatonin (MT) have emerged as valuable treatments to alleviate heavy metal-induced phytotoxicity. However, plants have not fully demonstrated the potential mechanisms by which these two hormones act under Ni and Cu stress. Herein, this study investigated the impact of individual and combined application of 24-EBR and MT on the growth and physiological traits of Primula forbesii Franch. subjected to stress (200 μmol L-1 Ni and Cu). The experiments compared the effects of different mitigation treatments on heavy metal (HM) stress and the scientific basis and practical reference for using these exogenous substances to improve HM resistance of P. forbesii in polluted environments. Nickel and Cu stress significantly hindered leaf photosynthesis and nutrient uptake, reducing plant growth and gas exchange. However, 24-EBR, MT, and 24-EBR + MT treatments alleviated the growth inhibition caused by Ni and Cu stress, improved the growth indexes of P. forbesii, and increased the gas exchange parameters. Exogenous MT effectively alleviated Ni stress, and 24-EBR + MT significantly alleviated the toxic effects of Cu stress. Unlike HM stress, MT and 24-EBR + MT activated the antioxidant enzyme activity (by increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), significantly reduced reactive oxygen species (ROS) accumulation, and regulated ascorbate and glutathione cycle (AsA-GSH) efficiency. Besides, the treatments enhanced the ability of P. forbesii to accumulate HMs, shielding plants from harm. These findings conclusively illustrate the capability of 24-EBR and MT to significantly bolster the tolerance of P. forbesii to Ni and Cu stress.

Effect of Green Light Replacing Some Red and Blue Light on Cucumis melo under Drought Stress

Light quality not only directly affects the photosynthesis of green plants but also plays an important role in regulating the development and movement of leaf stomata, which is one of the key links for plants to be able to carry out normal growth and photosynthesis. By sensing changes in the light environment, plants actively regulate the expansion pressure of defense cells to change stomatal morphology and regulate the rate of CO2 and water vapor exchange inside and outside the leaf. In this study, Cucumis melo was used as a test material to investigate the mitigation effect of different red, blue, and green light treatments on short-term drought and to analyze its drought-resistant mechanism through transcriptome and metabolome analysis, so as to provide theoretical references for the regulation of stomata in the light environment to improve the water use efficiency. The results of the experiment showed that after 9 days of drought treatment, increasing the percentage of green light in the light quality significantly increased the plant height and fresh weight of the treatment compared to the control (no green light added). The addition of green light resulted in a decrease in leaf stomatal conductance and a decrease in reactive oxygen species (ROS) content, malondialdehyde MDA content, and electrolyte osmolality in the leaves of melon seedlings. It indicated that the addition of green light promoted drought tolerance in melon seedlings. Transcriptome and metabolome measurements of the control group (CK) and the addition of green light treatment (T3) showed that the addition of green light treatment not only effectively regulated the synthesis of abscisic acid (ABA) but also significantly regulated the hormonal pathway in the hormones such as jasmonic acid (JA) and salicylic acid (SA). This study provides a new idea to improve plant drought resistance through light quality regulation.

Chitosan-fulvic acid nanoparticles enhance drought tolerance in maize via antioxidant defense and transcriptional reprogramming

Nanoparticles are promising alternatives to synthetic fertilizers in the context of climate change and sustainable agriculture. Maize plants were grown under gradient concentrations (50 μM, 100 μM, 200 μM, 500 μM, and 1 mM) of chitosan (Ch), fulvic acid (FA) or chitosan-fulvic acid nanoparticles (Ch-FANPs). Based on the overall phenotypic assessment, 100 μM was selected for downstream experiments. Maize plants grown under this optimized concentration were thereafter subjected to drought stress by water withholding for 14 days. Compared to the individual performances, the combined treatment of Ch-FANPs supported the best plant growth over chitosan, fulvic acid, or sole watered plants and alleviated the adverse effects of drought by enhancing root and shoot growth, and biomass by an average 20%. In addition, Ch-FANPs-treated plants exhibited a significant reduction in hydrogen peroxide (H2O2) content (~10%), with a concomitant increase in ascorbate peroxidase (APX) activity (>100%) while showing a reduced lipid peroxidation level observed by the decrease in malondialdehyde (MDA) content (~100%) and low electrolyte leakage level. Furthermore, chlorophyll content increased significantly (>100%) in maize plants treated with Ch-FANPs compared to Ch or FA and control in response to drought. The expression of drought-induced transcription factors, ZmDREB1A, ZmbZIP1, and ZmNAC28, and the ABA-dependent ZmCIPK3 was upregulated by Ch-FANPs. Owing to the above, Ch-FANPs are proposed as a growth-promoting agent and elicitor of drought tolerance in maize via activation of antioxidant machinery and transcriptional reprogramming of drought-related genes.

Comparative investigation on chemical and green synthesized titanium dioxide nanoparticles against chromium (VI) stress eliciting differential physiological, biochemical, and cellular attributes in Helianthus annuus L

Nanotechnology is a new scientific area that promotes unique concepts to comprehend the optimal mechanics of nanoparticles (NPs) in plants under heavy metal stress. The present investigation focuses on effects of synthetic and green synthesized titanium dioxide nanoparticles (TiO2 NPs and gTiO2 NPs) against Cr(VI). Green TiO2 NPs have been produced from plant leaf extract (Ricinus communis L.). Synthesis was confirmed employing an array of optical spectroscopic and electron microscopic techniques. Chromium strongly accelerated H2O2 and MDA productions by 227 % and 266 % at highest chromium concentration (60 mg/kg of soil), respectively, and also caused DNA damage, and decline in photosynthesis. Additionally, anomalies were observed in stomatal cells with gradual increment in chromium concentrations. Conversely, foliar applications of TiO2 NPs and gTiO2 NPs considerably mitigated chromium stress. Sunflower plants treated with modest amounts of green TiO2 NPs had significantly better growth index compared to chemically synthesized ones. Principal component analysis highlighted the variations among photosynthetic attributes, oxidative stress markers, and antioxidant defense systems. Notably, gTiO2 supplementation to the Cr(VI) strained plants minimized PC3 production which is a rare report so far. Conclusively, gTiO2 NPs have been identified to be promising nano-based nutrition resource for farming applications.

Sodium nitroprusside modulates oxidative and nitrosative processes in Lycopersicum esculentum L. under drought stress

KEY MESSAGE

Sodium nitroprusside mediates drought stress responses in tomatoes by modulating nitrosative and oxidative pathways, highlighting the interplay between nitric oxide, hydrogen sulfide, and antioxidant systems for enhanced drought tolerance. While nitric oxide (NO), a signalling molecule, enhances plant tolerance to abiotic stresses, its precise contribution to improving tomato tolerance to drought stress (DS) through modulating oxide-nitrosative processes is not yet fully understood. We aimed to examine the interaction of NO and nitrosative signaling, revealing how sodium nitroprusside (SNP) could mitigate the effects of DS on tomatoes. DS-seedlings endured 12% polyethylene glycol (PEG) in a 10% nutrient solution (NS) for 2 days, then transitioned to half-strength NS for 10 days alongside control plants. DS reduced total plant dry weight, chlorophyll a and b, Fv/Fm, leaf water potential (ΨI), and relative water content, but improved hydrogen peroxide (H2O2), proline, and NO content. The SNP reduced the DS-induced H2O2 generation by reducing thiol (-SH) and the carbonyl (-CO) groups. SNP increased not only NO but also the activity of L-cysteine desulfhydrase (L-DES), leading to the generation of H2S. Decreases in S-nitrosoglutathione reductase (GSNOR) and NADPH oxidase (NOX) suggest a potential regulatory mechanism in which S-nitrosylation [formation of S-nitrosothiol (SNO)] may influence protein function and signaling pathways during DS. Moreover, SNP improved ascorbate (AsA) and glutathione (GSH) and reduced oxidized glutathione (GSSG) levels in tomato plants under drought. Furthermore, the interaction of NO and H2S, mediated by L-DES activity, may serve as a vital cross-talk mechanism impacting plant responses to DS. Understanding these signaling interactions is crucial for developing innovative drought-tolerance strategies in crops.

Effects of environmental metal and metalloid pollutants on plants and human health: exploring nano-remediation approach

Metal and metalloid pollutants severely threatens environmental ecosystems and human health, necessitating effective remediation strategies. Nanoparticle (NPs)-based approaches have gained significant attention as promising solutions for efficient removing heavy metals from various environmental matrices. The present review is focused on green synthesized NPs-mediated remediation such as the implementation of iron, carbon-based nanomaterials, metal oxides, and bio-based NPs. The review also explores the mechanisms of NPs interactions with heavy metals, including adsorption, precipitation, and redox reactions. Critical factors influencing the remediation efficiency, such as NPs size, surface charge, and composition, are systematically examined. Furthermore, the environmental fate, transport, and potential risks associated with the application of NPs are critically evaluated. The review also highlights various sources of metal and metalloid pollutants and their impact on human health and translocation in plant tissues. Prospects and challenges in translating NPs-based remediation from laboratory research to real-world applications are proposed. The current work will be helpful to direct future research endeavors and promote the sustainable implementation of metal and metalloid elimination.

Dual sources of melatonin and evidence for different primary functions

This article discusses data showing that mammals, including humans, have two sources of melatonin that exhibit different functions. The best-known source of melatonin, herein referred to as Source #1, is the pineal gland. In this organ, melatonin production is circadian with maximal synthesis and release into the blood and cerebrospinal fluid occurring during the night. Of the total amount of melatonin produced in mammals, we speculate that less than 5% is synthesized by the pineal gland. The melatonin rhythm has the primary function of influencing the circadian clock at the level of the suprachiasmatic nucleus (the CSF melatonin) and the clockwork in all peripheral organs (the blood melatonin) via receptor-mediated actions. A second source of melatonin (Source # 2) is from multiple tissues throughout the body, probably being synthesized in the mitochondria of these cells. This constitutes the bulk of the melatonin produced in mammals and is concerned with metabolic regulation. This review emphasizes the action of melatonin from peripheral sources in determining re-dox homeostasis, but it has other critical metabolic effects as well. Extrapineal melatonin synthesis does not exhibit a circadian rhythm and it is not released into the blood but acts locally in its cell of origin and possibly in a paracrine matter on adjacent cells. The factors that control/influence melatonin synthesis at extrapineal sites are unknown. We propose that the concentration of melatonin in these cells is determined by the subcellular redox state and that melatonin synthesis may be inducible under stressful conditions as in plant cells.

Investigating the synergistic effects of biochar, trans-zeatin riboside, and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat

BACKGROUND

Water stress is a major danger to crop yield, hence new approaches to strengthen plant resilience must be developed. To lessen the negative effects of water stress on wheat plants, present study was arranged to investigate the role of synergistic effects of biochar, trans-zeatin riboside (t-ZR), and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat.

RESULTS

In a three-replication experiment comprising of four treatments (T0: Control, T1: Drought stress (DS), T2: DS + t-ZR with biochar, T3: DS + A. brasilense with biochar), we observed notable improvements in soil quality and enzymatic activities in water-stressed wheat plants with the application of t-ZR and A. brasilense with biochar. In drought stress, Treatment having the application of A. brasilense with biochar performs best as compared to the other and significant increased the enzymatic activities such as peroxidase (7.36%), catalase (8.53%), superoxide dismutase (6.01%), polyphenol oxidase (14.14%), and amylase (16.36%) in wheat plants. Different enzymatic activities showed different trends of results. Soil organic C, dissolved organic C, dissolved organic N also enhanced 29.46%, 8.59%, 22.70% respectively with the application of A. brasilense with biochar under drought stress condition.

CONCLUSIONS

The synergistic action of A. brasilense and biochar creates an effective microbiological environment that supports essential plant physiological processes during drought stress. This enhancement is attributed to improved soil fertility and increased organic matter content, highlighting the potential of these novel strategies in mitigating water stress effects and enhancing crop resilience.

Differentially Expressed Genes Identification of Kohlrabi Seedlings (Brassica oleracea var. caulorapa L.) under Polyethylene Glycol Osmotic Stress and AP2/ERF Transcription Factor Family Analysis

Osmotic stress is a condition in which plants do not get enough water due to changes in environmental factors. Plant response to osmotic stress is a complex process involving the interaction of different stress-sensitive mechanisms. Differentially expressed genes and response mechanisms of kohlrabi have not been reported under osmotic stress. A total of 196,642 unigenes and 33,040 differentially expressed unigenes were identified in kohlrabi seedlings under polyethylene glycol osmotic stress. AP2/ERF, NAC and eight other transcription factor family members with a high degree of interaction with CAT and SOD antioxidant enzyme activity were identified. Subsequently, 151 AP2/ERF genes were identified and analyzed. Twelve conserved motifs were searched and all AP2/ERF genes were clustered into four groups. A total of 149 AP2/ERF genes were randomly distributed on the chromosome, and relative expression level analysis showed that BocAP2/ERF genes of kohlrabi have obvious specificity in different tissues. This study lays a foundation for explaining the osmotic stress resistance mechanism of kohlrabi and provides a theoretical basis for the functional analysis of BocAP2/ERF transcription factor family members.