Search Results (160)

Heat stress caused a stagnation in the growth and development of Passiflora edulis Sims. To investigate the effects of high-temperature stress, this study subjected P. edulis to 40 °C treatment for different durations; the changes in chlorophyll content, chlorophyll fluorescence parameters, photosynthetic parameters, transcriptome profiles, and photosynthesis-related genes of P. edulis under high-temperature stress were analyzed. The results showed that after 5 h of heat stress, the chlorophyll content of the leaves decreased by 31%, variable fluorescence/maximum fluorescence (Fv/Fm) decreased by 26.91%, photochemical performance index (PI_abs) by 99.28%, comprehensive performance index (PI_total) by 94.20%, light energy absorbed per unit area (ABS/CSm) by 13.56%, light energy captured per unit area (TRo/CSm) by 17.90% and quantum yield of electron transfer per unit area (ETo/CSm) by 92.61%. The net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) decreased by 47%, 41% and 38%, respectively, while intercellular CO₂ concentration (Ci) increased by 1.34 times. Transcriptome sequencing results of P. edulis under heat stress identified 2336 differentially expressed genes (DEGs), which were significantly enriched in pathways including chloroplast function and plant hormone signal transduction. GO enrichment analysis demonstrated that DEGs were significantly enriched in terms related to catalytic activity and chloroplast components. Concurrently, KEGG pathway analysis revealed that carbon fixation in photosynthetic organisms was among the key pathways showing significant enrichment of these DEGs. The expression levels of photosynthesis-related genes, including PePSAE, PeMADs, PebHLH, PeFAR1, PePSBS, PePnsB4, PebZIP and PeC2H2, exhibited a significant increase after 3 h of high-temperature stress and rapidly declined following 5 h. These findings lay a foundation for further research on the high-temperature stress response mechanism and photosynthetic regulation of heat tolerance in P. edulis. Full article

Cortaderia selloana is an invasive grass spreading rapidly and becoming a serious environmental concern in many areas of the world. The species expanded to the Iberian Peninsula, including its eastern coast, where it increasingly occupies diverse ecosystems. This is the first evaluation of C. selloana’s tolerance to salinity and water deficit, combined with heat stress, during two key developmental stages: germination and early vegetative growth. Experimental trials were conducted using seeds and juvenile plants from two populations. Elevated temperature reduced germination, biomass accumulation, and shoot elongation, particularly when combined with water or salt stress. Drought exerted the strongest inhibitory effect on photosynthetic pigments, whereas salinity mainly affected carotenoid content, mostly in one of the populations analysed. Proline accumulation increased under drought and salinity, reaching up to 70 µmol·g⁻¹ DW, but to a lesser extent when combined with a heat treatment, suggesting enhanced proline catabolism at high temperature. Total soluble sugars tended to increase under water deficit (from ~75 to >100 mg equivalent of glucose g⁻¹ DW), indicating a potential osmoprotective shift from proline to carbohydrates. These results highlight intraspecific variability in stress tolerance and emphasise that C. selloana’s success in Mediterranean environments depends on its capacity to withstand transient but not prolonged combined stresses. Full article

This study sought to screen 45 maize (Zea mays L.) inbred lines for tolerance to combined drought and heat stress (CDHS) and identify the leaf proteome patterns of two inbred lines with contrasting stress response at early vegetative stage. Biomass accumulation was significantly reduced under CDHS compared to optimum conditions. Furthermore, CDHS-tolerant inbred lines exhibited significantly lower (p < 0.05) leaf temperatures (28.6 °C) and higher sub-stomatal CO₂ concentration (9012 mol mol⁻¹) and photosynthetic yield (0.69) under stress. The tolerant (CIM18) and susceptible (QS21) inbred lines were exposed to stress by maintaining a field capacity of 25% for 7 days and increasing the daily ambient temperature by 5 °C from 25 °C to 40 °C. Conventional two-dimensional electrophoresis analysis was used to compare leaf protein expression profiles, and significant differences (p < 0.05) were observed. Out of a total of 505 proteins, 114 showed significant quantitative variation. Of these, 62 proteins had a twofold upregulation in CIM18, while 52 were downregulated. Twenty upregulated proteins were selected for amino acid micro-sequencing, and 11 proteins were uniquely expressed in CIM18. The other nine proteins had ≥ twofold upregulation in CIM18 compared to QS21. The functions of the identified proteins included defence, metabolism, photosynthesis and structure. Full article

Global warming and soil salinization pose significant challenges to modern plant cultivation. Background/Objectives: Polyploidization of whole-genome duplication is an important evolutionary strategy, enhancing plant adaptation to environmental stress. This study investigates the impact of heat and salt stress on photosynthesis and proteomic changes in a polyploid series of Arabidopsis thaliana (diploid, triploid, and tetraploid). Methods: Two-month-old plants were exposed to heat stress (45 °C for 3 h) or salt stress (300 mM NaCl for 24 or 48 h). Stress effects were assessed via photosystem II maximum efficiency (F_v/F_m), the performance index (PI_ABS), and proline content. Proteomic responses were analyzed using 2D SDS-PAGE and mass spectrometry. Results: Our findings revealed that polyploid plants maintained higher photosynthetic performance than diploids under both heat and salt stress. While proline accumulation under heat stress was comparable across all ploidy levels, polyploids accumulated more proline under salt stress, indicating enhanced salinity tolerance. Proteomic analysis showed differential protein expression among diploid and polyploid plants in response to stress. Several differentially expressed proteins had functions involved in photosynthesis and stress response pathways. These findings confirm prior evidence of tetraploid Arabidopsis resilience to salinity and extend this observation to heat stress. Moreover, triploids also demonstrated increased stress tolerance, suggesting adaptive advantages of this intermediate ploidy level as well. Conclusions: Differential expression patterns among ploidy levels may reflect varied energy-saving strategies and alterations in protein structure and function. This work highlights the importance of polyploidy in improving plant stress resilience, offering insights for breeding stress-tolerant crops in a changing climate. Full article

Global temperature rise has become a critical challenge to agricultural sustainability, severely affecting crop growth, productivity, and survival. Human-induced climate change and greenhouse gas emissions cause heat stress, disrupting plant metabolism and physiology at all developmental stages from germination to harvest. Elevated temperatures during germination impair water uptake, enzyme activity, and energy metabolism, leading to poor or uneven seedling emergence. At key phases such as flowering and grain filling, heat stress limits photosynthesis and transpiration by inducing stomatal closure, restricting carbon dioxide intake, and reducing photosynthetic efficiency. The reproductive stage is particularly vulnerable to high temperatures, impairing pollen viability, preventing anther dehiscence, and reducing fertilization success. Membrane instability further accelerates chlorophyll degradation and leaf senescence. Heat stress also alters biochemical and hormonal balances by disrupting the synthesis and signaling of auxins, gibberellins, and abscisic acid (ABA). Elevated ABA promotes stomatal closure to enhance stress tolerance, while increased ethylene levels trigger premature leaf senescence and abscission. These hormonal shifts and oxidative stress hinder plant growth and reproduction, threatening global food security. Although plants employ adaptive mechanisms such as heat shock protein expression and stress-responsive gene regulation, current strategies remain inadequate, highlighting the urgent need for innovative approaches to improve crop resilience under rising temperatures. Full article

Acetolactate synthase (ALS) is an important enzyme in plant branched-chain amino acid biosynthesis and the target of several major herbicide classes. Despite its agronomic importance, the role of ALS genes in stress adaptation in the invasive weed Amaranthus palmeri remains unstudied. In this study, four ApALS genes with high motif conservation were identified and analyzed in A. palmeri. Phylogenetic analysis classified ApALS and other plant ALS proteins into two distinct clades, and the ApALS proteins were predicted to localize to the chloroplast. Gene expression analysis demonstrated that ApALS genes are responsive to multiple stresses, including salt, heat, osmotic stress, glufosinate ammonium, and the ALS-inhibiting herbicide imazethapyr, suggesting roles in both early and late stress responses. Herbicide response analysis using an Arabidopsis thaliana ALS mutant (AT3G48560) revealed enhanced imazethapyr resistance, associated with higher chlorophyll retention. Furthermore, high sequence homology between AT3G48560 and ApALS1 suggests a conserved role in protecting photosynthetic function during herbicide stress. This study provides the first comprehensive analysis of the ALS gene family in A. palmeri and offers important insights into its contribution to stress resilience. These findings establish a vital foundation for developing novel strategies to control this pervasive agricultural weed and present potential genetic targets for engineering herbicide tolerance in crops. Full article

This study investigates the effects of rising temperatures on photosynthetic efficiency and stress tolerance in major Greek grapevine cultivars by using Sauvignon Blanc and Merlot as references. Muscat and Assyrtiko displayed the most heat-tolerant photosynthetic apparatus among the white cultivars, while Mavrodafni was the most heat-tolerant among the red ones, by effectively managing excess light energy. Sauvignon Blanc, although exhibiting heat susceptibility, maintained high photosystem II (PSII) functionality under heat stress by activating photoprotective mechanisms. Savvatiano and Agiorgitiko were more vulnerable to photo-oxidative stress above 35 °C, while Agiorgitiko maintained a functional photosynthetic apparatus, even at 40 °C, by shifting to a more photoprotective strategy. In contrast, Merlot, despite its resistance to photo-oxidative stress, lacked photoprotective investment, resulting in suppressed PSII under heat stress. Moschofilero was the most susceptible cultivar to photo-oxidative stress. Leaf morphological traits also contributed to heat stress tolerance, with smaller, thicker leaves facilitating thermoregulation. The present results provide important insights into specific responses to heat stress of major Greek grapevine cultivars. This knowledge may aid in selecting heat-tolerant genotypes and optimizing vineyard site selection, thereby enhancing the sustainability and climate resilience of viticulture. Full article

Meta-cresol (m-cresol) is highly corrosive and toxic, and is widely present in industrial wastewater. As a pollutant, it adversely affects various aspects of human production and daily life. To evaluate the feasibility of using sunflowers to remediate m-cresol-contaminated wastewater, this study used Helianthus annuus L. as the test subject to analyze its tolerance and the wastewater purification efficiency under different m-cresol concentrations. The results showed that the net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), and light energy utilization efficiency (LUE) of Helianthus annuus L. exhibited an overall decreasing trend, while the intercellular CO₂ concentration (Cᵢ) initially increased and subsequently decreased with increasing m-cresol concentration. When m-cresol concentration reached or exceeded 60 mg·L⁻¹, the net photosynthetic rate and intercellular CO₂ concentration in the leaves showed opposite trends with further increases in m-cresol stress. The inhibition of net photosynthesis in sunflowers by m-cresol was mainly attributed to non-stomatal factors. The maximum photochemical efficiency (F_v/F_m), actual photochemical efficiency (ΦPSII), photochemical quenching coefficient (q^P), PSII excitation energy partition coefficient (α), and the fraction of absorbed light energy used for photochemistry (P) all decreased with increasing m-cresol concentration. In contrast, non-photochemical quenching (NPQ), the quantum yield of regulated energy dissipation [Y(NPQ)], and the fraction of energy dissipated as heat through the antenna (D) first increased and then decreased. Under low-concentration m-cresol stress, sunflowers protected their photosynthetic system by dissipating excess light energy as heat as a stress response. However, high concentrations of m-cresol caused irreversible damage to Photosystem II (PSII) in sunflowers. Under m-cresol stress, chlorophyll a exhibited strong stability with minimal degradation. As the m-cresol concentration increased from 30 to 180 mg·L⁻¹, the removal rate decreased from 84.91% to 11.84%. In conclusion, sunflowers show good remediation potential for wastewater contaminated with low concentrations of m-cresol and can be used for treating m-cresol wastewater with concentrations ≤ 51.9 mg·L⁻¹. Full article

Drought stress is a major constraint on plant photosynthesis, growth, and yield, particularly in the context of increasingly frequent and severe extreme weather events driven by global climate change. Enhancing photosynthetic efficiency and abiotic stress tolerance is therefore essential for sustaining crop productivity. In this study, we functionally characterized Kalanchoë fedtschenkoi NAC83 (KfNAC83), a transcription factor derived from a heat-tolerant obligate crassulacean acid metabolism (CAM) species, by constitutively overexpressing it in the C₃ model plant Arabidopsis thaliana. Transgenic Arabidopsis lines overexpressing KfNAC83 exhibited significantly enhanced tolerance to water-deficit and NaCl stress, along with improved photosynthetic performance, biomass accumulation, and overall productivity. Transcriptomic analysis revealed that KfNAC83 overexpression increased key components of the jasmonate (JA) signaling pathway in both roots and shoots, suggesting a mechanistic link between KfNAC83 activity and enhanced abiotic stress responses. Additionally, the transgenic lines displayed increased nighttime decarboxylation activity, indicative of partial CAM-like metabolic traits. These findings demonstrate that KfNAC83 functions as a positive regulator of abiotic stress tolerance and growth, likely through modulation of jasmonate-mediated signaling and photosynthetic metabolism. This work highlights the potential of CAM-derived transcription factors for bioengineering abiotic stress-resilient crops in the face of climate change. Full article

Passion fruit (Passiflora edulis) is an economically important fruit worldwide. However, heat stress severely threatens its production, particularly in tropical and subtropical regions. To elucidate the molecular and metabolic mechanisms underlying heat tolerance, comparative physiological, transcriptomic, and metabolomic analyses were conducted between two yellow passion fruit cultivars: heat-tolerant ‘Summer Queen’ (F2) and heat-sensitive ‘Qinmi 9’ (QM9). Physiological evaluations demonstrated that QM9 exhibited significantly lower heat tolerance than F2, manifesting as severe leaf wilting, impaired photosynthetic efficiency, and elevated reactive oxygen species (ROS) accumulation. F2 exhibited distinct metabolic and transcriptional adaptations under heat stress, particularly in purine metabolism and flavonoid biosynthesis. Metabolites such as glutamine, xanthine, luteoloside, and trifolin were enriched in F2, alongside the upregulation of genes like adenosine kinase (AK), xanthine dehydrogenase (XDH), guanine deaminase (GDA), and flavonoid 3′-hydroxylase (F3′H). Weighted gene co-expression network analysis (WGCNA) highlighted strong associations between these pathways and transcription factors (e.g., MYB, HSF, WRKY), suggesting their pivotal roles in heat adaptation. Exogenous application of xanthine and trifolin markedly enhanced heat tolerance in passion fruit. Furthermore, knockdown of PeGDA and PeXDH markedly altered the heat tolerance of F2. These findings reveal that elevated metabolites in purine metabolism and flavonoid biosynthesis enhance heat tolerance in passion fruit, offering new insights into the molecular mechanisms of heat tolerance and potential targets for breeding climate-resilient passion fruit varieties. Full article

The escalating demand for sustainable agriculture calls for innovative strategies that enhance crop resilience while minimizing dependence on synthetic fertilizers. This study evaluated the synergistic effects of a microbial consortium (PYS), organic fertilizer (OF), glycine (Gly), and indole-3-acetic acid (IAA) on lettuce under heat stress. The experiment was conducted in a greenhouse in Bangkok, Thailand, simulating tropical high-temperature conditions. The PYS+OF+Gly treatment significantly improved fresh weight, matching the performance of chemical fertilizer (CF) and indicating a strong growth-promoting synergy. Chlorophyll a, chlorophyll b, and carotenoid contents were higher in PYS or PYS+OF treatment, suggesting enhanced photosynthetic efficiency. At 60 days, PYS-based treatments also led to substantial increases in total phenolics and flavonoids, coupled with reduced lipid peroxidation and elevated antioxidant activities (DPPH, APX, CAT, POD, and SOD). However, vitamin C levels remained highest in the CF and OF controls, indicating a potential metabolic shift toward phenylpropanoid rather than ascorbate biosynthesis. Overall, our results demonstrate that combining microbial consortia with organic and biostimulant inputs could enhance growth, stress tolerance, and the nutritional quality of lettuce. This integrated approach presents a promising strategy for climate-resilient crop production and warrants further validation across different crops, environmental settings, and large-scale agricultural systems. Full article

Flavonoids serve as crucial plant antioxidants in drought tolerance, yet their antioxidant regulatory mechanisms within mycorrhizal plants remain unclear. In this study, using a two-factor design, trifoliate orange (Poncirus trifoliata (L.) Raf.) seedlings in the four-to-five-leaf stage were either inoculated with Funneliformis mosseae or not, and subjected to well-watered (70–75% of field maximum water-holding capacity) or drought stress (50–55% field maximum water-holding capacity) conditions for 10 weeks. Plant growth performance, photosynthetic physiology, leaf flavonoid content and their antioxidant capacity, reactive oxygen species levels, and activities and gene expression of key flavonoid biosynthesis enzymes were analyzed. Although drought stress significantly reduced root colonization and soil hyphal length, inoculation with F. mosseae consistently enhanced the biomass of leaves, stems, and roots, as well as root surface area and diameter, irrespective of soil moisture. Despite drought suppressing photosynthesis in mycorrhizal plants, F. mosseae substantially improved photosynthetic capacity (measured via gas exchange) and optimized photochemical efficiency (assessed by chlorophyll fluorescence) while reducing non-photochemical quenching (heat dissipation). Inoculation with F. mosseae elevated the total flavonoid content in leaves by 46.67% (well-watered) and 14.04% (drought), accompanied by significantly enhanced activities of key synthases such as phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), 4-coumarate:coA ligase (4CL), and cinnamate 4-hydroxylase (C4H), with increases ranging from 16.90 to 117.42% under drought. Quantitative real-time PCR revealed that both mycorrhization and drought upregulated the expression of PtPAL1, PtCHI, and Pt4CL genes, with soil moisture critically modulating mycorrhizal regulatory effects. In vitro assays showed that flavonoid extracts scavenged radicals at rates of 30.07–41.60% in hydroxyl radical (•OH), 71.89–78.06% in superoxide radical anion (O₂^•−), and 49.97–74.75% in 2,2-diphenyl-1-picrylhydrazyl (DPPH). Mycorrhizal symbiosis enhanced the antioxidant capacity of flavonoids, resulting in higher scavenging rates of •OH (19.07%), O₂^•− (5.00%), and DPPH (31.81%) under drought. Inoculated plants displayed reduced hydrogen peroxide (19.77%), O₂^•− (23.90%), and malondialdehyde (17.36%) levels. This study concludes that mycorrhizae promote the level of total flavonoids in trifoliate orange by accelerating the flavonoid biosynthesis pathway, hence reducing oxidative damage under drought. Full article

Global warming has resulted in an increase in the frequency of extreme high-temperature events. High temperatures can increase cell membrane permeability, elevate levels of osmotic adjustment substances, reduce photosynthetic capacity, impair plant growth and development, and even result in plant death. Under high-temperature stress, plants mitigate damage through physiological and biochemical adjustments, heat signal transduction, the regulation of transcription factors, and the synthesis of heat shock proteins. However, different plants exhibit varying regulatory abilities and temperature tolerances. Investigating the heat-resistance and regulatory mechanisms of plants can facilitate the development of heat-resistant varieties for plant genetic breeding and landscaping applications. This paper presents a systematic review of plant physiological and biochemical responses, regulatory substances, signal transduction pathways, molecular mechanisms—including the regulation of heat shock transcription factors and heat shock proteins—and the role of plant hormones under high-temperature stress. The study constructed a molecular regulatory network encompassing Ca²⁺ signaling, plant hormone pathways, and heat shock transcription factors, and it systematically elucidated the mechanisms underlying the enhancement of plant thermotolerance, thereby providing a scientific foundation for the development of heat-resistant plant varieties. Full article

The functional role of MAPKK genes in potato (Solanum tuberosum L.) under high-temperature stress remains unexplored, despite their critical importance in stress signaling and yield protection. We characterized StMAPKK1, a novel group D MAPKK localized to plasma membrane/cytoplasm. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed cultivar-specific upregulation in potato (‘Atlantic’ and ‘Desiree’) leaves under heat stress (25 °C, 30 °C, and 35 °C). Transgenic lines overexpressing (OE) StMAPKK1 exhibited elevated antioxidant enzyme activity, including ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), mitigating oxidative damage. Increased proline and chlorophyll accumulation and reduced oxidative stress markers, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), indicate improved cellular redox homeostasis. The upregulation of key antioxidant and heat stress-responsive genes (StAPX, StCAT1/2, StPOD12/47, StFeSOD2/3, StMnSOD, StCuZnSOD1/2, StHSFA3 and StHSP20/70/90) strengthened the enzymatic defense system, enhanced thermotolerance, and improved photosynthetic efficiency, with significant improvements in net photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (Gs) under heat stress (35 °C) in StMAPKK1-OE plants. Superior growth and biomass (plant height, plant and its root fresh and dry weights, and tuber yield) accumulation, confirming the positive role of StMAPKK1 in thermotolerance. Conversely, RNA interference (RNAi)-mediated suppression of StMAPKK1 led to a reduction in enzymatic activity, proline content, and chlorophyll levels, exacerbating oxidative stress. Downregulation of antioxidant-related genes impaired ROS scavenging capacity and declines in photosynthetic efficiency, growth, and biomass, accompanied by elevated H₂O₂ and MDA accumulation, highlighting the essential role of StMAPKK1 in heat stress adaptation. These findings highlight StMAPKK1’s potential as a key genetic target for breeding heat-tolerant potato varieties, offering a foundation for improving crop resilience in warming climates. Full article

Bangiales are photosynthetic organisms that grow in the intertidal zone, a region characterized by fluctuating environmental conditions. The order comprises genera exhibiting two different morphological variations, filamentous and foliose. It was recently demonstrated that the filamentous alga ‘Bangia’ sp. ESS1 possesses the intrinsic ability to “memorize” an experience of prior heat stress to enhance its survival under subsequent, normally lethal, high-temperature conditions via the acquisition of heat stress tolerance. Here, we investigated whether foliose red algae can similarly memorize heat stress to acquire thermotolerance. When Pyropia yezoensis thalli were primed with non-lethal, high-temperature treatments (22 and 25 °C) for 7 days, vegetative cells subsequently triggered with a normally lethal temperature of 30 °C showed dramatically increased survival rates, indicating that P. yezoensis can acquire heat stress tolerance via exposure to non-lethal high temperatures. In addition, when 22 °C-primed thalli were incubated at 15 °C for recovery, vegetative cells survived subsequent incubation at 30 °C; their survival rates varied depending on the duration of recovery. These findings indicate that, like filamentous red algae, the foliose species P. yezoensis memorizes heat stress to acquire tolerance to recurrent thermostress. The identification of heat stress memory in foliose Bangiales lays a foundation for improving the heat stress tolerance of these important algae, supporting the sustainability of the nori mariculture industry. Full article