Search Results (260)

Climate change is placing global agriculture under growing pressure, as plants must withstand extreme environmental conditions such as drought and high salinity, both inducing osmotic and oxidative stress. As part of their survival strategies, plants accumulate protective molecules (osmolytes), including the amino acid proline. For decades, plant biology has largely assumed that high proline accumulation under stress signals strong stress tolerance. However, this review challenges that “proline-centric” perspective. Analyses across a wide range of plant species reveal a more complex picture. Stress-induced proline accumulation is not universal: in some species, proline levels remain relatively unchanged, with other metabolites acting as functional osmolytes, or increase only in response to artificially applied severe stress conditions. Even when proline increases, its absolute concentrations may be too low to contribute significantly to osmotic adjustment. Nevertheless, proline may still be involved in stress tolerance mechanisms through its additional roles, detoxifying reactive oxygen species (ROS), directly stabilising proteins or acting as a stress signalling molecule. Comparative analyses of genetically related taxa with varying degrees of stress tolerance sometimes show negative correlations between proline accumulation and tolerance, with higher proline concentrations measured in the most sensitive genotypes. Overall, the evidence indicates that proline‘s role in plant survival is highly context-dependent and strongly influenced by genetic background and must therefore be evaluated on a case-by-case basis. Distinguishing whether proline acts as an adaptive defence or merely as a biochemical marker of physiological strain under stress is essential for accurately assessing plant stress tolerance. Full article

Globally, approximately 1.4 billion hectares of land are affected by soil salinity, necessitating effective and field-applicable remediation strategies. This study aimed to evaluate the growth performance, ion regulation, physiological responses, and phytodesalination potential of ice plant (Mesembryanthemum crystallinum L.) under field conditions with varying salinity levels in coastal Taiwan across winter and spring seasons. Soil salinity and sodicity across the three experimental fields (low, moderate, and high) were characterized using electrical conductivity (EC), exchangeable Na, the Na/K ratio, and exchangeable sodium percentage (ESP). Plant performance and salt removal efficiency were evaluated through field cultivation and biochemical analysis. Ice plant could successfully grow and produce harvestable biomass across all salinity levels, although growth and biomass declined with increasing soil salinity. Pronounced seasonal differences were observed in both plant performance and salt removal efficiency. Winter conditions, characterized by lower temperature and reduced evaporative demand, favored biomass accumulation and Na uptake, resulting in substantially higher phytodesalination capacity, with estimated NaCl removal of approximately 1256–1826 kg ha⁻¹ per cropping cycle. In contrast, spring conditions with higher temperatures, longer sunshine duration, and increased evapotranspiration significantly reduced biomass production and Na removal efficiency. Correspondingly, osmolytes such as proline, ononitol, and D-pinitol, along with total phenolic content (TPC), were significantly elevated in spring-grown plants, suggesting enhanced osmotic adjustment and antioxidant defense. However, the variation in the half-maximal inhibitory concentration (IC₅₀) values suggested that the plant’s antioxidant capacity was not solely a function of total phenolic content but resulted from complex interactions among different antioxidant compounds under heightened environmental stress. Overall, this field study provides strong empirical evidence that M. crystallinum is a highly salt-tolerant species with significant, season-dependent phytodesalination potential. Winter cultivation is particularly effective for the sustainable management and amelioration of coastal salt-affected agricultural soils. Full article

Heavy metal pollution has become a major environmental challenge limiting agricultural productivity worldwide. Copper (Cu), although an essential micronutrient, becomes phytotoxic at elevated concentrations, primarily by inducing oxidative stress. Among the most widespread metabolic adjustments triggered by abiotic stress is the accumulation of proline, which is a compatible osmolyte that stabilizes proteins and membranes and helps maintain cellular redox homeostasis. This paper demonstrates that the heterologous expression of TsPAP1, a triticale gene encoding a prolyl aminopeptidase, enhances proline accumulation and confers increased Cu tolerance in Arabidopsis thaliana. Under Cu stress, transgenic lines maintained superior physiological performance relative to the wild type (WT), as evidenced by the reduced biomass loss and lower accumulation of malondialdehyde and reactive oxygen species. Cu exposure activated antioxidant defenses; however, the induction of catalase (CAT), class III peroxidases (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) activities was more pronounced in transgenic lines. Transcriptomic analysis revealed a higher expression of genes encoding antioxidant isoforms localized to chloroplasts (sAPX, CSD2), the cytosol (APX1), peroxisomes (CAT1), and the apoplast (Prx02, Prx51), indicating targeted reinforcement of the multi-compartmental redox defense system. Together, these findings identify TsPAP1 as a potential regulator of proline-dependent redox homeostasis that contributes to enhanced Cu tolerance through the coordinated activation of antioxidant networks. The results further suggest that PAP-dependent peptide turnover contributes to proline-mediated stress adaptation, linking peptide metabolism with antioxidant regulation and highlighting TsPAP1 as a promising target for engineering heavy metal-resilient crops. Full article

Drought increasingly threatens terrestrial vegetation, whereas current syntheses remain disproportionately focused on seed plants. Ferns and mosses provide a useful contrast because they represent distinct hydration strategies among early-diverging land plants. We compiled 3272 paired observations from 46 drought experiments covering 35 fern species and 41 moss species to compare responses in water status, photosynthesis, chlorophyll fluorescence, oxidative stress, osmotic adjustment, abscisic acid, and growth. Drought reduced physiological performance in both groups, but mosses showed a greater mean decline than ferns. Ferns maintained stable maximum quantum yield and increased nonphotochemical quenching despite reduced pigment content and carbon assimilation, suggesting stronger photoprotective regulation. In contrast, mosses showed coordinated declines in maximum fluorescence, effective PSII yield, and maximum quantum yield, together with elevated minimum fluorescence, indicating direct PSII impairment. Oxidative damage, osmolyte accumulation, and growth suppression were also stronger in mosses. Within ferns, drought sensitivity was concentrated in epiphytic species, especially obligate, canopy, tank-forming, and xerophytic groups. Fern responses were partly explained by provenance climate, drought duration, and specific leaf area. Overall, within the species and experimental conditions represented in the current dataset, ferns largely maintain photochemical stability through photoregulation, whereas mosses shift more rapidly toward PSII impairment, oxidative injury, and growth suppression, highlighting vulnerable components of moisture-dependent ecosystems under intensifying drought. Full article

Drought is among the most serious abiotic stresses affecting tomato production worldwide, especially under climate change. Plants exposed to repeated drought events may develop stress memory, allowing them to respond more efficiently to subsequent stress exposure. In this study, physiological and transcriptomic tools were combined to investigate dehydration stress memory in tomato (Solanum lycopersicum L.). Tomato plants were subjected to two consecutive drought stresses separated by a recovery stage, where control (C), first stress (S1), rehydration (H), and second stress (S2) stages were analyzed. Physiological measurements showed progressive reductions in relative water content (RWC) and PSII activity under drought stress, while proline accumulation was significantly increased during the second stress stage, indicating memory-associated adaptive responses. RNA sequencing revealed dramatic transcriptome reprogramming with thousands of differentially expressed genes (DEGs) across stress stages. Hierarchical clustering identified 30 distinct expression patterns among revealed DEGs, including clusters associated with transcriptional memory, adaptive responses, metabolic adjustment, and recovery processes. Several memory-associated clusters were enriched with transcription factors, signaling proteins, osmolyte-related genes, and reactive oxygen species detoxification enzymes. Gene Ontology analysis highlighted significant enrichment of pathways related to photosynthesis, response to water deprivation, ABA signaling, oxidative stress, carbohydrate metabolism, and chromatin organization. Recovery-associated expression of histone and chromatin remodeling genes indicates a potential involvement of epigenetic-related regulatory processes in dehydration stress memory in tomato. Tomato plants respond to repeated dehydration stress through coordinated physiological, metabolic, transcriptional, and epigenetic adjustments that improve stress adaptation. The identified candidate memory genes may provide useful targets for future breeding programs aimed at enhancing drought tolerance in tomato. Full article

Drought impairs osmotic adjustment and photosynthetic performance in legumes; however, the role of micronutrients in modulating these responses across genotypes remains unclear. This study investigated the effects of selenium on the osmolytes and photosynthetic efficiency in two vegetable-soybean (Glycine max L. Merrill) cultivars differing in drought responses: UVE14 (drought-tolerant) and UVE17 (drought-susceptible). Plants were grown under well-watered (100% soil water-holding capacity, WHC) and water-limited (30% soil WHC) conditions, with or without soil-applied selenium. Free amino acids, soluble sugars, chlorophyll pigments, vegetation indices, and chlorophyll fluorescence parameters were assessed at the flowering and pod-filling stages. Under drought conditions, selenium enhanced tolerance primarily by modulating free amino acid metabolism at flowering, increasing aspartate, asparagine, glutamine, and glutamate levels, alongside improvements in chlorophyll content, canopy greenness, and PSII photochemical efficiency. These responses indicate a coordinated adjustment between nitrogen metabolism and photosynthetic function. Both cultivars benefited from selenium application, although the responses were more pronounced in the susceptible cultivar (UVE17). Selenium-induced changes in soluble sugar content were greater under well-watered conditions in both cultivars. The limited accumulation of stress-associated osmolytes, such as proline, following selenium soil drench suggests reduced cellular disruption and mitigation of drought-induced stress. These findings highlight selenium as a context-dependent modulator of drought resilience and emphasize cultivar- and developmental stage-specific effects. Full article

Global warming exacerbates high-temperature stress, disturbing the growth, metabolic homeostasis and quality formation of tea plants (Camellia sinensis L.). Trehalose, a multifunctional osmolyte, can enhance abiotic stress tolerance, but its systematic metabolic mechanism against heat damage in tea remains unclear. Here, we applied integrated gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) non-targeted metabolomics to compare control (CK), heat-stressed (T), and trehalose-treated heat-stressed (TT) tea leaves. We identified 163 differential volatile metabolites in GC-MS and 1619 differential non-volatile metabolites in LC-MS. Metabolite classification showed that organic oxygen compounds dominated differential volatile metabolites, while lipids and lipid-like molecules dominated differential non-volatile metabolites. The Kyoto Encyclopedia of Genes and Genomes enrichment showed that alanine, aspartate and glutamate metabolism, arginine biosynthesis, aminoacyl-tRNA biosynthesis, and flavone and flavonol biosynthesis were core shared pathways. Quantitatively, exogenous trehalose under heat stress significantly increased carbohydrate accumulation, restored lipid homeostasis, and elevated alanine, arginine, and related intermediates, thereby maintaining carbon–nitrogen balance. Trehalose also remodeled the amino acid substrate pool for aminoacyl-tRNA biosynthesis. In flavonoid metabolism, trehalose enhanced high-antioxidant flavonoid aglycones while reducing most glycosides and inhibiting excessive hydroxylation of flavonols. Although total flavonoid content decreased in TT relative to T, this reflected alleviated oxidative damage and reduced dependence on flavonoid-based defense. Combined with total amino acid and flavonoid quantifications, we conclude that exogenous trehalose enhances tea plant thermotolerance by coordinately regulating primary amino acid metabolism and secondary flavonoid metabolism. These findings provide a theoretical basis for using trehalose in heat-resistance cultivation and quality improvement of tea plants. Full article

The Sugars Will Eventually be Exported Transporters (SWEET) family plays a crucial role in the carbohydrate distribution, phloem loading, and stress response of plants, yet the evolutionary characteristics and functional diversification of SWEET genes in the endangered timber species Phoebe bournei (Hemsl.) Yen C. Yang remain largely unexplored. In this study, 21 PbSWEET genes were identified and classified into four subfamilies (A–D). Subfamily A exhibited a unique lineage expansion, mainly driven by tandem and segmental duplications. The nonsynonymous-to-synonymous substitution ratio (Ka/Ks) values of all duplicate gene pairs were all less than 1, indicating a strong selective suppression effect; consistent with this evolutionary constraint, the majority of PbSWEET proteins harbor the conserved Medicago truncatula Nodulin 3/saliva (MtN3_slv) domain, with only a few exceptions lacking a complete version. Promoter and hormone response analyses revealed that under abscisic acid (ABA) stress, PbSWEET4 exhibited an immediate burst, whereas PbSWEET10 showed a delayed burst. Physiological data indicated that soluble sugars may be more dominant osmolytes than proline (Pro), a pattern that points to a potential carbon-centric regulatory strategy. PbSWEET4 showed an early burst before sugar/oxidative peaks, suggesting a possible non-canonical signaling role, whereas PbSWEET10 exhibited a late increase coinciding with sugar/malondialdehyde (MDA) peaks, suggesting potential involvement in sugar redistribution. Under methyl jasmonate (MeJA) treatment, PbSWEET10 was rapidly induced, yet sugar accumulation occurred only at 24 h, a temporal decoupling that suggests a possible transcription–metabolism decoupling. Collectively, these correlative patterns point to a possible dual-wave transcriptional mechanism and nominate PbSWEET10 as a candidate for stress response, though these inferences require functional validation. Full article

Bryophytes are key components of acid–soil ecosystems; however, their capacity for aluminum (Al) accumulation and tolerance remains poorly understood. In this study, bryophytes and a limited number of pteridophyte and lichen species were collected from acidic soils of tea plantations and adjacent forest stands in the Caspian region of northern Iran and analyzed. Nearly all bryophyte specimens exhibited Al concentrations above the critical accumulation threshold (1000 µg g⁻¹ DW), with some reaching values exceeding 28,000 µg g⁻¹ DW, confirming their strong accumulation capacity. After Al, iron was the most abundantly accumulated metal (1430–22,800 µg g⁻¹ DW), followed by manganese (100–3100 µg g⁻¹ DW). The sampled lichen species accumulated Al at concentrations between 1063 and 9154 µg g⁻¹ DW, while Al levels in the aerial parts of pteridophytes rarely exceeded the critical threshold; when they did, accumulation occurred predominantly in old and fertile fronds rather than sterile ones. Three field-collected bryophyte species—Barbula unguiculata, Palamocladium euchloron, and Hypnum cupressiforme—were acclimated to laboratory conditions and treated with two Al levels (without or with 150 µM Al, pH 4.0) for 12 weeks. The leafy shoots were analyzed for their antioxidant response, osmolyte accumulation, phenolic metabolism, callose deposition, and carboxylic-acid profile. Histochemical analyses revealed predominant localization of Al in cell walls, associated with enrichment of pectin and uronic acids. These responses were most pronounced in H. cupressiforme, followed by P. euchloron, and least evident in B. unguiculata. Elevated levels of intracellular detoxification compounds—phenolics, flavonoids, and carboxylic acids (tartaric, oxalic, malic, and citric acids)—were detected, again with species-specific differences. Overall, the results reveal that bryophytes employ multiple physiological strategies to tolerate Al toxicity, with substantial interspecific variation. These findings emphasize their ecological significance and provide a foundation for future research on the physiological and evolutionary mechanisms underlying Al tolerance and accumulation in early land plants. Full article

Plants are constantly exposed to diverse abiotic stresses, including drought, salinity, and extreme temperatures, which severely limit growth, development, and crop productivity. These stresses disrupt physiological, biochemical, and molecular processes, leading to reduced photosynthesis, altered water and ion homeostasis, and accumulation of reactive oxygen species (ROS). Plants have evolved sophisticated sensing and signaling mechanisms to perceive these stresses, with phytohormones playing central roles in mediating adaptive responses. Key hormones, including abscisic acid (ABA), salicylic acid (SA), jasmonates (JAs), gibberellins (GAs), auxin (IAA), ethylene (ET), melatonin, and strigolactones (SLs), regulate stress tolerance by controlling stomatal behavior, root architecture, antioxidant systems, osmolyte accumulation, and stress-responsive gene expression. Importantly, these hormones operate within an intricate network of crosstalk, integrating multiple signaling pathways to balance growth and stress adaptation. Interactions among ABA, GA, JA, SA, auxin, ET, SLs, and melatonin enable plants to coordinate transcriptional regulation, protein phosphorylation, and ROS signaling, optimizing survival under fluctuating environmental conditions. Understanding the molecular mechanisms underlying hormonal crosstalk and their roles in abiotic stress tolerance provides valuable insights for developing resilient crops in the face of climate change. Full article

Selenium (Se) biofortification is a promising approach to improve the nutritional value and functional quality of microgreens, although species-specific responses to Se remain insufficiently understood. This study investigated the effects of Se biofortification on physiological status, antioxidant responses, phenolic composition, and molecular changes in four Brassica microgreens: broccoli, kohlrabi, pak choi, and kale, using biochemical analyses, HPLC, and FTIR spectroscopy. The indicators of nutritional quality and stress-related metabolism in Brassica microgreens showed species-specific responses due to selenium treatment. Kohlrabi showed coordinated osmotic and metabolic adjustment involving osmolyte accumulation and enhanced antioxidant response, although moderate membrane sensitivity was observed at the highest selenium concentration. Pak choi maintained tolerance through balanced metabolic adjustment and enzymatic defense, while broccoli responded predominantly through enzymatic antioxidant mechanisms. Kale exhibited pronounced non-enzymatic responses, including anthocyanin accumulation and enhanced radical scavenging capacity. PCA confirmed species-specific response strategies and differential associations among biochemical parameters. Changes in antioxidant functionality were associated with both metabolite accumulation and structural reorganization of phenolic-related compounds. Overall, Se biofortification improved functional and nutritional traits of the investigated Brassica microgreens, although higher selenium concentrations induced moderate oxidative and membrane-related stress in certain Brassica microgreens. These findings highlight the importance of species-specific optimization of Se application to maximize crop quality while minimizing potential effects of Se toxicity. Full article

Osmolytes, including proline, soluble sugars, and glycine betaine (GB), are essential for plant adaptation to environmental stress. They contribute to osmotic adjustment, membrane stabilization, and the protection of cellular functions in arid and saline habitats. This study investigated major osmolytes (mainly proline and soluble sugars) in native Qatari plant species in natural field conditions and their physiological adaptation strategies. Significant interspecific variation indicated diverse mechanisms of stress acclimation. Although proline accumulation was common, it did not consistently correlate with salinity tolerance, which suggests that its accumulation may reflect stress-induced metabolic imbalance and adaptation rather than being a reliable indicator of resistance. Plant species, including crops and native plants such as Avicennia marina, Halopeplis perfoliata, Limonium axillare, Tetraena qatarensis, and Ochradenus baccatus, are presented as examples supporting this pattern. In contrast, the relative balance between soluble sugars and proline indicates coordinated carbon–nitrogen regulation that supports osmotic homeostasis and growth in fluctuating environmental conditions. Halophytic species exhibited distinct osmolyte profiles that highlight the potential role of additional compatible solutes (particularly GB) in stress adaptation. However, its occurrence and functional significance in these species have been insufficiently characterized. Given the predominance of C₃ photosynthesis in Qatari flora, GB may also help mitigate photorespiratory stress in extreme conditions. The findings expand the current understanding of osmotic regulation in desert plants and highlight the potential of biotechnological approaches to enhance crop tolerance of harsh environments by manipulating compatible solutes. Full article

Temperature stress strongly affects plant metabolism, and recurrent heat exposure can modify physiological responses depending on developmental stage. This study examined the biochemical and physiological adjustments of Senecio madagascariensis subjected to single (naïve) or repeated (primed) heat stress at 40 °C during vegetative and reproductive stages. Sampling was conducted after the second heat stress and after the subsequent recovery period. Principal component analyses (PCAs) revealed marked stage-specific contrasts. In the vegetative stage, PCA1 and PCA2 explained 75.7% of total variance, clearly separating treatments: naïve plants were associated with elevated proline, soluble sugars, phenolics, glycine betaine, hydrogen peroxide (H₂O₂) and lipid peroxidation, whereas primed plants were linked to enhanced superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities and reduced oxidative markers. Under stress, naïve plants showed substantial increases in soluble sugars (+198%) and proline (+66.9%), whereas primed plants exhibited attenuated oxidative responses and reduce phenolic accumulation. After recovery, primed plants exhibited markedly reduced H₂O₂ levels (−57.5%) and lipid peroxidation, alongside higher SOD activity. In the reproductive stage, PCA indicated more subtle priming effects, with overlapping clusters among treatments. Primed plants accumulated the highest soluble sugar levels under stress (+276.5%), while naïve plants showed higher proline and glycine betaine levels. Following recovery, osmolyte levels were similar among groups. Senecionine remained unchanged during the vegetative stage but increased in both naïve (+21.4%) and primed (+19.1%) plants during the reproductive stage after recovery. Oxidative markers revealed contrasting patterns, with primed reproductive plants showed the lowest superoxide under stress but the highest H₂O₂ and lipid peroxidation at both time points. Overall, the findings demonstrate that heat-stress responses in S. madagascariensis are developmentally regulated, with stronger priming effects during vegetative growth and phenology-dependent metabolic adjustments during reproduction. All results are directly supported by the measured biochemical and physiological data. Full article

The roles of proline in stress tolerance, energy metabolism, immune function, and ecology across organisms suggest a broader relevance in orchard agroecosystems than is often recognized. In fruit trees, stress-induced proline accumulation reflects a complex regulatory network, while evidence also indicates that inter-organ transport contributes to protective responses under abiotic stress. In insects, proline functions as an oxidative substrate priming the rest-to-flight metabolic transition in pollinators and pests, a cryoprotective osmolyte and a structural element of conserved classes of antimicrobial peptides against microbial threats. These roles create paradoxical orchard-scale feedbacks while a stress-protective molecule both intensifies herbivore pressure and enhances pollination and biocontrol services. The orchard environment represents a meeting point of plant, environmental, animal and human health, reflecting the integrative logic of the One Health framework, where proline emerges as a highly water-soluble and bioactive compound. The functional homology between insect and human proline catabolism emerges governance-critical issues across tree physiology, insect immunity and human dietary exposure. The targeted application offers a unifying framework for farmers, scientists and policymakers to advance Sustainable Development Goal commitments across food security, human health, climate resilience and biodiversity. We conclude that proline supplementation in orchards requires regulatory monitoring across ecophysiological and pharmaceutical dimensions. Full article

Plants in agricultural systems rarely face single stressors; instead, they encounter concurrent biotic (pathogen, pests) and abiotic (drought, salinity, heavy metals) stresses that causes severely reduce crop yields and endanger food security. The traditional methods of breeding, genetic engineering, and agrochemicals tend to target individual stresses and still do not suffice in the complex field conditions. Compared to these approaches, nanotechnology offers distinct advantages: nanoparticles (NPs) can be applied as foliar sprays or seed treatments without lengthy breeding cycles or regulatory hurdles associated with genetically modified organisms. However, nanotechnology is not inherently “better” but rather complementary to crop engineering; each approach has specific strengths. Breeding and genetic engineering provide heritable, long-term solutions, while nanotechnology offers immediate, season-specific, and reversible interventions. Cross-tolerance, the phenomenon whereby exposure to one stress enhances tolerance to another, offers a promising alternative. This review critically examines how NPs act as stress-priming agents that induce cross-tolerance by activating overlapping defense networks, including antioxidant systems (SOD, CAT, APX), phytohormonal crosstalk (ABA, SA, JA), osmolyte homeostasis, and stress-responsive gene expression. We synthesize current evidence on NP uptake, translocation, and cellular interactions, and evaluate their dual role in directly suppressing pathogens while simultaneously enhancing plant immune responses and physiological resilience. However, efficacy is highly dose-dependent: low, subtoxic doses prime defense through hermetic ROS signaling, whereas supraoptimal doses cause phytotoxicity. The current challenges in nano-mediated stress alleviation include: (i) a persistent laboratory-to-field translation gap, with field outcomes averaging only 60–70% of greenhouse efficacy; (ii) dose-dependent phytotoxicity; (iii) poor reproducibility across studies; (iv) scalability and formulation stability issues; and (v) insufficient understanding of long-term environmental fate, including soil accumulation, non-target organism effects, and food chain safety. Future research should consider field-validated formulations (e.g., SiNPs, ZnONPs, Fe₃O₄NPs) across major staple crops); integrating nanotechnology with precision agriculture through nanosensors, remote sensing, and artificial intelligence for site-specific, dose-optimized applications;developing smart, biodegradable nanoparticles with stimuli-responsive release; and establishing harmonized regulatory frameworks for nano-agrochemical approval. When deployed responsibly, nanoparticle-induced cross-tolerance represents a sustainable approach to improve crop resistance against multifactorial stress, with significant implications for climate-resilient agriculture and global food security. Full article