Search Results (159)

Graphene oxide (GO) is a carbon-based nanomaterial explored for agricultural and forestry uses, but plant responses are strongly subject to both the dose and the route of exposure. We summarized recent studies with defined graphene oxide (GO) exposures by seed priming, foliar delivery, and root or soil exposure, while comparing annual crops with woody forest plants. Mechanistic progress points to a shared physicochemical basis: surface oxygen groups and sheet geometry reshape water and ion microenvironments at the soil–seed and soil–rhizosphere interfaces, and many reported shifts in antioxidant enzymes and hormone pathways likely represent downstream stress responses. In crops, low-to-moderate doses most consistently improve germination, root architecture, and tolerance to salinity or drought stress, whereas high doses or prolonged root exposure can cause root surface coating, oxidative injury, and photosynthetic inhibition. In forest plants, evidence remains limited and often relies on seedlings or tissue culture. For forest plants with long life cycles, processes such as soil persistence, aging, and multi-seasonal carry-over become key factors, especially in nurseries and restoration substrates. The available data indicate predominant root retention with generally limited root-to-shoot translocation, so residues in edible and medicinal organs remain insufficiently quantified under realistic-use patterns. This review provides a scenario-based framework for crop- and forestry-specific safe-dose windows and proposes standardized endpoints for long-term fate and ecological risk assessment. Full article

Applying non-thermal plasma (NTP) to seeds prior to sowing is recognized for its ability to enhance germination and promote plant growth. This study investigated the effects of NTP seed treatment on alfalfa seed surface characterization, germination, growth, and biochemical traits under varying water conditions. NTP modified seed surface properties by decreasing water contact angle, roughening the coat, and reducing O–H/N–H and C–H band intensities, while major functional groups remained intact. Short plasma exposures (<2 min) enhanced germination, whereas prolonged treatment (10 min) reduced viability, indicating embryo sensitivity. In pot experiments, both 1 and 5 min treatments improved fresh and dry weight, stem and root elongation, pigment accumulation, and protein content, particularly under normal and moderate water stress, while extended exposure (10 min) offered limited benefits and could be detrimental under severe drought. Root growth was most responsive, suggesting enhanced water and nutrient uptake. Plasma had modest effects on polyphenols and flavonoids but influenced early physiological responses and antioxidant activity. These findings highlight NTP as a promising seed priming tool to improve alfalfa performance, though further studies are needed to clarify the mechanisms and specific contributions of plasma components. Full article

The lack of protocols for breaking seed dormancy, inconsistent seed quality, and abiotic stress factors such as drought impede large-scale restoration efforts of pollinator-friendly native plant species. This research explores the germination response, dormancy-breaking techniques, and water stress tolerance in selected pollinator-friendly plant species with characteristics facilitating mechanized rehabilitation protocols and biodiversity enhancement. Forty-two commercial seed lots representing seven plant families with 28 species were evaluated under two alternating temperature regimes (15/25 °C and 20/30 °C) with and without gibberellic acid (GA₃) priming treatments. Six of the twenty-eight species were selected based on pollinator requirements for the monarch butterfly (Danaus plexippus L.) and further examined by priming seeds for 24 h in solutions containing GA₃, kinetin (KIN), and hydrogen peroxide (H₂O₂), or their combinations, to evaluate their dormancy-breaking responses. The effect of water stress on seed germination was assessed in controlled chambers at soil water potentials of −1.08, −0.75, −0.13, and 0 MPa. Initial seed quality of the 42 seed lots revealed that only 62% had greater than 50% germination, while of the same 42 lots, 98% had greater than 50% viability based on the commercial seed label. The difference was largely attributed to seed dormancy. In laboratory studies of the 42 seed lots, GA₃ significantly enhanced germination percentage, and reduced T₅₀ (time to 50% germination) across most seed lots. Overall, germination was higher and faster at 20/30 °C than 15/25 °C. Priming the six selected species with 1.0 mM GA₃ in 0.3% H₂O₂ consistently improved germination compared to the non-primed control after 14 days. Asclepias species (A. incarnata, A. syriaca, and A. tuberosa) exhibited consistently high germination across a broad moisture range of −0.75 to 0 MPa. In contrast, Echinacea purpurea required high moisture levels (−0.13 to 0 MPa) for optimal germination. Monarda fistulosa and Rudbeckia hirta showed their best performance under moderate moisture conditions (−0.13 MPa). Collectively, the use of GA₃ priming to break physiological seed dormancy offers a promising approach to enhance germination and improving the establishment potential of native pollinator species in restoration programs. Full article

Essential oils (EOs) are volatile, aromatic, and hydrophobic extracts of plant origin, known for their complex chemical composition, which often includes over 300 natural molecules with low molecular weights. They are extracted from various plant organs through physical–mechanical processes or dry distillation, and their qualitative composition and quantity change depending on the species, cultivar, and environmental growth conditions. They play a key role in plants’ response to abiotic stresses, such as drought and salinity, whose effects are intensified by climate change. Several studies showed that drought and salinity can increase or decrease EO production, depending not only on the plant species but also on the severity of the stress; in fact, in many crops an enhancement of EO synthesis was often observed under mild stress, whereas moderate or severe stress reduced production. For a few years, EOs have been considered important biostimulants and bioprotectors, capable of replacing chemical pesticides in sustainable agriculture. Consequently, seed pre-treatments (e.g., seed priming or seed coating) with EOs may represent promising tools to improve germination, stress tolerance, and crop productivity under stress conditions. Nevertheless, the high costs of extraction of EOs and the little evidence collected from field experiments still limit their use in agronomic applications. The aim of this review was to gather the most important information, published over the last ten years, concerning the effects of drought and salinity on the production of EOs and their use as biostimulants. This review critically examines the available literature, highlighting a positive perspective towards the adoption of natural approaches to reduce the environmental impact of agricultural production. Current results indicate encouraging progress in the application of EOs as biostimulants; however, further studies are needed to verify their effectiveness in real agronomic environments. Full article

Frequent extreme weather events exacerbate agricultural abiotic stress, with drought causing widespread yield loss. Tomato, a globally important vegetable sensitive to water deficit, has been predominantly studied under single-drought scenarios that poorly reflect recurrent field conditions. This study investigated physiological and molecular responses of two tomato genotypes to repeated drought stress. Results showed that the drought-sensitive genotype ‘TGTB’ exhibited faster ABA accumulation and more pronounced ABA-mediated stomatal closure. During the second drought cycle, stomatal pore length and width were significantly smaller than during the first drought, indicating a strong stress memory effect. In contrast, the drought-tolerant ‘LA1598’ showed minimal memory responses. Under extreme drought stress, primed and non-primed ‘TGTB’ plants showed significantly lower H₂O₂ content than controls, whereas primed ‘LA1598’ plants maintained a significantly lower O₂^·− production rate than non-primed plants during both extreme drought cycles. Antioxidant enzyme systems contributed to ROS homeostasis, supported by the regulation of key drought-responsive genes. This study demonstrates genotype-dependent memory capacity and reveals that drought priming enhances repeated drought tolerance through ABA-regulated stomatal adjustment. These findings provide a theoretical basis for improving tomato resilience to recurrent drought and supporting breeding of drought-tolerant varieties. Full article

Drought is a major abiotic stress that compromises seed germination, seedling establishment, and subsequent crop productivity, thereby threatening agricultural sustainability and food security. Developing effective seed-based strategies is therefore essential to enhance drought resilience. In this study, we investigated the efficacy of green-synthesized silver nanoparticles (AgNPs), produced using Azadirachta indica (neem) flower extract as a seed priming agent, to improve drought tolerance and early growth in wheat (Triticum aestivum). Seeds were primed with AgNPs (25–100 mg L⁻¹), PEG 6000 (−0.6, −0.8, and −1.0 MPa), and their combination (AgNPs + PEG 6000). AgNP priming enhanced germination by 72%, 86%, and 100% at 25, 50, and 75 mg L⁻¹, respectively, compared with the control, with 75 mg L⁻¹ identified as the optimal concentration. This treatment increased total chlorophyll and carotenoid contents by 14% and 6%, and elevated phenolic and flavonoid accumulation by 58% and 97%, respectively. Antioxidant enzyme activities were also substantially increased—catalase (CAT) by 44%, superoxide dismutase (SOD) by 23%, peroxidase (POX) by 11%, and glutathione reductase (GR) by 58%. Under drought stress, AgNP priming at 75 mg L⁻¹ improved germination by up to 80%, indicating enhanced drought tolerance. Elevated protein and antioxidant enzyme levels, along with reduced malondialdehyde (MDA), proline, and total soluble sugar levels, further confirmed mitigation of oxidative stress. Collectively, these results demonstrate that neem-mediated green-synthesized AgNPs could serve as an effective seed-priming agent, promoting wheat seedling establishment and enhancing drought resilience under water-deficit conditions. Full article

Plants continuously face multiple abiotic stresses, including drought, salinity, heat, cold, and heavy metal, that challenge cellular homeostasis and threaten global crop productivity. Recent research reveals that these stress responses are not isolated but interconnected through shared hormonal, redox, and transcriptional networks. This review provides an integrative synthesis of current advances in stress signaling, emphasizing how perception, transduction, and memory layers are hierarchically organized across distinct stress types. We outline key regulatory hubs—such as ABA-centered hormonal crosstalk, chloroplast-nucleus redox communication, and epigenetic priming—that coordinate systemic tolerance. Furthermore, we highlight emerging evidence for stress-specific modules that operate under combined stresses (e.g., drought–heat, salinity–cold), providing a unified framework for understanding how plants integrate multi-dimensional signals. This synthesis offers a conceptual perspective linking signaling architecture to adaptive outcomes, aiming to inform future strategies for engineering multi-stress-resilient crops. Full article

Ultrafine bubble (UFB) priming has recently emerged as a promising technique to enhance seed germination, yet its physiological mechanisms remain unclear. This study investigated the effects of UFB priming on adzuki bean (Vigna angularis) seeds under stress-free and drought conditions. Four treatments were tested: Control (non-primed), DW (primed with distilled water), UFB1 (4.56 × 10⁷ particles/mL), and UFB2 (1.13 × 10⁸ particles/mL). For priming, seeds were immersed in each solution at 25 ± 1 °C for 24 h. Seed traits, including water uptake, coat thickness, and total reactive oxygen species (ROS) levels in the priming solutions and seeds, were analyzed. UFB priming reduced seed coat thickness and slowed early water uptake without affecting final moisture content. Total ROS levels displayed a concentration-dependent pattern, with higher UFB increasing ROS in water but reducing them on the seed surface. Under stress-free conditions, all priming treatments accelerated germination, although higher UFB slightly prolonged T50. Under drought simulated by polyethylene glycol (PEG 10 and 15%), non-primed seeds were strongly inhibited, whereas primed seeds maintained high germination rates (>97%). Our results demonstrated that UFB priming improved water uptake, seed coat structure, and ROS signaling, enhancing seed performance of adzuki bean under favorable and drought conditions. Full article

Drought stress severely affects the physio-biochemical processes and yield of nutritious crops like vegetable soybean (Glycine max L. Merrill), threatening global food security and emphasising the need for effective strategies to improve drought tolerance. This study, conducted under controlled conditions in a greenhouse, investigates the effects of three selenium application methods (seed priming, foliar spray, and soil application) on photosynthesis efficiency, relative water content (RWC), hydrogen peroxide (H₂O₂), antioxidative responses, and yield traits of two vegetable soybean cultivars, UVE14 (drought-tolerant) and UVE17 (drought-susceptible), under drought stress. Among the three Se application methods, soil application was the most effective in improving drought tolerance and yield performance in both cultivars. In UVE17 (drought-susceptible), soil application significantly increased the number of seeds per plant (SPP) and the number of pods per plant (PPP), while in UVE14 (drought-tolerant) SPP increased. Selenium foliar spray and seed priming treatments did not increase yield in drought-stressed UVE14, suggesting that they are unlikely to further enhance tolerance in drought-tolerant cultivars. For UVE17 under drought conditions, selenium soil application improved key physio-biochemical indicators of drought tolerance, including photosynthesis efficiency (total performance of photosystems I and II, total chlorophyll content, and stomatal conductance), water retention (RWC), and carotenoid content. These improved physio-biochemical responses directly impacted yield outcomes. Notably, RWC and total chlorophyll content at the pod-filling stage in drought-stressed UVE17 were positively correlated with an increase in PPP under selenium soil application. Selenium soil application stands out as the most effective method for enhancing drought tolerance in vegetable soybean, presenting a promising and practical solution for enhanced crop production under climate change. Full article

One way to counteract the effects of environmental stresses, including drought, is to use products with growth-promoting properties for plants. Such agents include quercetin, which is known for its antioxidant and photosynthesis-enhancing properties. In the conducted experiment, the influence of the quercetin–copper complex (Q-Cu (II)) treatment, characterized by strong high solubility in water and strong antioxidant properties, was investigated. The pot experiment demonstrated the effect of spraying with Q-Cu (II) solutions (0.01, 0.05 and 0.1%) on wheat plants growing under drought stress conditions. Two treatments of Q-Cu (II) solutions were applied, and chlorophyll content and chlorophyll fluorescence (the maximum quantum yield of photosystem II (PSII) photochemistry (F_v/F_m), the efficiency of the water-splitting complex on the donor side of PSII (F_v/F_o), and the photosynthetic efficiency index (PI)), as well as gas exchange (photosynthetic network intensity (P_N), transpiration rate (E), stomatal conductance (g_s) and intercellular CO₂ concentration (C_i)), were measured 1 and 7 days after each treatment. In addition, antioxidant enzyme activity (catalase (CAT), peroxidase (SOD) and guaiacol peroxidase (GPOX)) and reactive oxygen species (ROS) levels were determined. Drought stress caused a decrease in chlorophyll content, and values of parameters F_v/F_m, F_v/F_o, PI and P_N, E, g_s, C_i, as well as an increase in ROS levels and antioxidant enzyme activity. Exogenous Q-Cu (II) improved photosynthetic indices and modulated redox status in a dose-dependent manner: 0.01–0.05% reduced ROS, whereas 0.1% increased ROS while concomitantly enhancing antioxidant enzyme activities and photosynthetic performance, consistent with ROS-mediated priming. The conducted research indicates the possibility of using Q-Cu (II) as a product to enhance the efficiency of the photosynthetic process under drought stress. Full article

Water deficit is a limitation to maize (Zea mays L.) productivity, and seed physiological conditioning (priming) is a strategy to mitigate its effects. Niobium (Nb), an abundant element in the Earth’s crust and crucial for emerging technologies, is primarily produced and exported by Brazil, particularly in the state of Minas Gerais. However, its behavior in soil and effects on plants remain poorly understood. This study evaluated the impact of maize seed hydropriming with different solutions, including ammonium niobate (V) oxalate (C₄H₄NNbO₉), on germination, seedling physiological performance under water deficit, and recovery after rehydration. The experiment was conducted in a greenhouse using a randomized block design with eight treatments and five replications. The germination speed index (GSI) was recorded over a period of seven days. Water deficit was imposed on day eight by suspending irrigation for seven days, followed by rehydration until day 21. Morphological, biochemical, and physiological traits were evaluated, including biomass, pigments, oxidative stress, antioxidant activity, starch, and osmolytes, with photosynthetic parameters measured during rehydration. Hydropriming with Nb-enhanced seed germination but also induced oxidative stress and reduced biomass accumulation. Nb seed priming affected photosynthetic performance in a treatment-dependent manner, leading to phototoxic effects. Overall, although Nb shows biostimulant potential by improving maize germination, its use under water-deficit conditions may trigger toxic responses associated with increased oxidative stress and growth inhibition. These findings highlight the need for further studies to define safe and effective Nb concentrations for improving drought tolerance. Full article

Addressing damage inflicted by environmental stress is difficult post-occurrence. The use of externally delivered gamma-aminobutyric acid (GABA) priming to healthy plants may serve as an effective preventive measure by stimulating plant defense pathways. A genome-wide transcriptional investigation was performed on tomato plants following GABA priming, with extended data about the stress memory of previously primed plants subjected to drought stress. GABA significantly stimulates starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism, porphyrin metabolism, glycerolipid metabolism, biosynthesis of phenylalanine, tyrosine, and tryptophan, phenylalanine metabolism, ascorbate and aldarate metabolism, pantothenate and CoA biosynthesis, and plant hormone signal transduction pathways. The initial priming effect could be remembered when subsequent environmental stress arose, but its influence intensified in plants that had previously undergone priming. The application of GABA can establish a novel form of preventative defense against the detrimental effects of stresses. It can effectively enhance long-term plant defense by facilitating the development of plant stress memory. Full article

The document is an updated review, starting from the Special Issue “Molecular Breeding for Abiotic Stress Tolerance in Crops” published in the Int. J. Mol. Sci. It reviews molecular breeding strategies to enhance abiotic stress tolerance in crops, addressing challenges like drought, salinity, temperature extremes, and waterlogging, which threaten global food security. Climate change intensifies these stresses, making it critical to develop resilient crop varieties. Plants adapt to stress through mechanisms such as hormonal regulation (e.g., ABA, ethylene), antioxidant defense (e.g., SOD, CAT), osmotic adjustment (e.g., proline accumulation), and gene expression regulation via transcription factors like MYB and WRKY. Advanced tools, such as CRISPR/Cas9 genome editing, enable precise modifications of stress-related genes, improving tolerance without compromising yield. Examples include rice (OsRR22, OsDST) and wheat (TaERF3, TaHKT1;5). Epigenetic regulation, including DNA methylation and histone modifications, also plays a role in stress adaptation. Specific studies focused on polyamine seed priming for improved germination and stress resistance, cadmium detoxification mechanisms, and genome-wide association studies (GWAS) to identify genetic markers for salt tolerance and yield. Research on salinity tolerance in wheat emphasizes sodium exclusion and tissue tolerance mechanisms. Future perspectives focus on genetic engineering, molecular markers, epigenetic studies, and functional validation to address environmental stress challenges, including the use of AI and machine learning to manage the large amount of data. The review underscores the importance of translating molecular findings into practical applications to ensure sustainable crop production under changing climates. Full article

Surfactants are widely utilized in agriculture as emulsifying, dispersing, anti-foaming, and wetting agents. In these adjuvant roles, the inherent biological activity of the surfactant is secondary to the active ingredients. Here, the hydrophilic non-ionic surface-active tri-block copolymer Pluronic^® F68 is investigated for direct biological activity in wheat. F68 binds to and inserts into lipid membranes, which may benefit crops under abiotic stress. F68’s interactions with Triticum aestivum (var Juniper) seedlings and a seed-borne Bacillus spp. endophyte are presented. At concentrations below 10 g/L, F68-primed wheat seeds exhibited unchanged emergence. Root-applied fluorescein-F68 (fF68) was internalized in root epidermal cells and concentrated in highly mobile endosomes. The potential benefit of F68 in droughted wheat was examined and contrasted with wheat treated with the osmolyte, glycine betaine (GB). Photosystem II activity of droughted plants dropped significantly below non-droughted controls, and no clear benefit of F68 (or GB) during drought or rehydration was observed. However, F68-treated wheat exhibited increased transpiration values (for watered plants only) and enhanced shoot dry mass (for watered and droughted plants), not observed for GB-treated or untreated plants. The release of seed-borne bacterial endophytes into the spermosphere of germinating seeds was not affected by F68 (for F68-primed seeds as well as F68 applied to roots), and the planktonic growth of a purified Bacillus spp. seed endophyte was not reduced by F68 applied below the critical micelle concentration. These studies demonstrated that F68 entered wheat root cells, concentrated in endosomes involved in transport, significantly promoted shoot growth, and showed no adverse effects to plant-associated bacteria. Full article

Droughts are predicted to intensify with climate change, posing a serious threat to global crop production. Increasing drought tolerance in plants requires an understanding of the underlying mechanisms. This study measured the physiological, phytohormonal and transcriptomic responses to drought in two apple rootstocks to identify drought ‘biomarkers’ and investigated whether the application of acibenzolar-S-methyl (ASM) to the roots could enhance drought tolerance. Two potted-plant trials were conducted on dwarfing (M9) and semi-dwarfing (CG202) apple rootstocks. In both trials, the response patterns in the roots and leaves were compared between irrigated and non-irrigated plants over a 14-day period. In trial 2, ASM was applied 14 days before and immediately before withdrawing irrigation. Drought induced significant decreases in transpiration, photosynthesis and stomatal conductance in both trials. This was accompanied by the accumulation of abscisic acid (ABA) metabolites and the upregulation of ABA pathway transcripts (CYP707A1/A2 and NCED3), a decrease in 12-oxophytodienoic acid (cis-OPDA) and the downregulation of ABA receptor genes (PYL4). The responses to drought were greater in the roots than the leaves, broadly similar across both rootstocks, but differed in strength and timing between the rootstocks. The application of ASM to the roots did not significantly affect the responsiveness to drought in either rootstock. The identified phytohormonal and transcriptomic biomarkers require further validation across a broader range of genotypes. Full article