Search Results (59)

Mikania micrantha, commonly known as mile-a-minute weed, is listed among the world’s top 10 worst weeds. Although native to humid regions of South America, it has recently been found to colonize arid habitats as well. Despite pronounced seasonal hydroclimatic variations in South China and increasing drought due to global climate change, the mechanisms underlying M. micrantha’s drought tolerance remain poorly understood. In this study, we compared the photosynthetic responses of M. micrantha leaves and stems between the dry (June) and wet (December) seasons through field experiments. We measured changes in phenotype, photosynthetic characteristics, and the content of antioxidant and osmotic adjustment substances, using the co-occurring native vine Paederia scandens as a control. The results revealed that during the dry season, M. micrantha leaves exhibited wilting, along with significant reductions in relative water content (RWC), chlorophyll (Chl), soluble sugar (SS), and soluble protein (SP). In contrast, the stems of M. micrantha maintained relatively stable phenotypes and chlorophyll levels compared to those of P. scandens. Notably, M. micrantha stems exhibited significant increases in vessel wall thickness, vessel density, total phenol content, and the activities of peroxidase (POD) and ascorbate peroxidase (APX). Furthermore, compared to P. scandens, M. micrantha stems displayed a greater increase in cortex proportion, flavonoid content, and soluble protein content. Expression analysis of bZIP transcription factors further revealed drought-responsive upregulation of specific genes (bZIP60, ZIP42-1), suggesting their potential involvement in drought response. These results indicate that although the leaves of M. micrantha are susceptible to prolonged drought, the stems exhibit considerable resilience, which may be attributed to a combination of traits including structural modifications in stem anatomy, enhanced antioxidant capacity, and osmotic adjustment. These insights suggest that stem-specific adaptations are key to its drought tolerance, providing a theoretical foundation for understanding the habitat distribution of M. micrantha and informing effective management strategies. Full article

Fulvic acid’s potential to enhance plant growth has been recognized, but its effects on plant growth and nutrient uptake under nutrient stress remain unclear. This experiment investigated the effects of fulvic acid at concentrations of 0 mg L⁻¹ (T1), 30 mg L⁻¹ (T2), 60 mg L⁻¹ (T3), 90 mg L⁻¹ (T4), 120 mg L⁻¹ (T5), and 150 mg L⁻¹ (T6) on the growth performance of two rice varieties—Jikedao 654 (J 654) and Jiyang 100 (J 100)—under low-nitrogen stress in a hydroponic system. The effects of different fulvic acid application rates on the growth and photosynthetic characteristics, the key enzymes of nitrogen metabolism, antioxidant properties, and the osmotic adjustment substances of rice under low-nitrogen stress were evaluated. The results indicated that the addition of an appropriate concentration of fulvic acid could enhance the growth performance of J 654 and J 100 under low-nitrogen stress. Compared to T1 treatment, the total dry weight and nitrogen accumulation of rice showed greater increases in response to T3 and T4 treatments. The photosynthetic pigment content increased, photosynthesis was enhanced, and the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO₂ concentration (Ci), and transpiration rate (Tr) were improved. The activities of key enzymes in nitrogen metabolism, including nitrate reductase (NR), glutamine synthetase (GS), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase activity (GPT), were enhanced, thereby improving the capacity for nitrogen uptake and assimilation. The addition of fulvic acid also enhanced the antioxidant capacity, increased the superoxide dismutase (SOD), peroxide (POD) and catalase (CAT) activity and decreased the toxic effects of ROS, the production rate of O₂⁻, and the hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content. The low-nitrogen stress was alleviated, thereby reducing the proline and soluble sugars content. Overall, it was demonstrated that adding an appropriate concentration (60–90 mg L⁻¹) of fulvic acid under low-nitrogen stress has a positive impact on the growth and development of rice. Our findings provide a theoretical basis for the application of fulvic acid in alleviating low-nitrogen stress in rice. Full article

Machilus thunbergii Siebold & Zucc. is recognized as an excellent tree species for landscaping and shelter forest. Excessive drought can affect the changes of physiological and biochemical substances in plants. However, little is known at present regarding the drought stress of M. thunbergii seedlings. In this paper, matrix water content, the anatomical structure of leaves, relative water content of leaves, and physiological characteristics index of leaves under droughting stress were dynamically observed. Droughting stress led to the wilting of M. thunbergii leaves, gradual closure of stomata on leaf epidermis, increases in stomatal density, gradual loosening of leaf cell structure arrangement, a thickening in leaf palisade tissue, and reductions in spongy tissue. Droughting stress caused the relative water content of the cultivation substrate to decline, the cultivation substrate reached the moderate drought level, and the seedlings began to die. Droughting stress led to the destruction of activity and balance of the leaf protective enzyme system, excessive accumulation of free radicals, the destruction of enzyme structure and function, and the production of lipid peroxidation product MDA. Droughting stress reduced the relative water content of leaves as a whole, the content of osmotic adjustment substances proline and soluble protein continued to decline, and a large number of electrolyte leakage in cells, causing serious damage to seedlings. Full article

PYR/PYL (pyrroloquinoline quinone resistance/PYR1-like) are receptors for abscisic acid (ABA) in plants and play a crucial role in responses to abiotic stress. In this study, we identified 63 members of the StPYL gene family at the tetraploid whole-genome level in potatoes. We analyzed the physicochemical properties of these 63 StPYLs and constructed a phylogenetic tree using Arabidopsis thaliana and potato (Solanum tuberosum L.) cultivar ‘DM’ as the reference. By examining gene structure, conserved protein motifs, and collinearity, we found that StPYLs are highly conserved throughout evolution. The gene expression heat map under salt stress revealed that 57 StPYL genes are involved in the salt stress response. Among them, the expression level of StPYL9a-like changed significantly under salt stress. Through genetic transformation, we observed that overexpression of StPYL9a-like enhanced the growth and survival of potato plants under salt stress compared to the wild type. The contents of proline (Pro), superoxide dismutase (SOD), and chlorophyll in the leaves of overexpressing plants increased, while malondialdehyde (MDA) levels decreased. This suggests that StPYL9a-like positively regulates salt tolerance by affecting antioxidant enzyme activity and osmotic adjustment substances in potatoes. Subcellular localization demonstrated that StPYL9a-like is localized in the nucleus. This study provides a reference for the functional research of PYLs in potatoes, offers a basis for screening potato genes related to salt stress, and lays a foundation for developing salt-tolerant potato varieties. Full article

In recent years, high temperature and drought have severely impacted the growth and development of loquat [Eriobotrya japonica (Thunb.) Lindl.] plants. Although dopamine can improve the stress resistance of plants, its role in combined stress requires further exploration. This study investigated the alleviative effect and mechanism of exogenous dopamine on loquat seedlings subjected to the combined stress of high temperature and drought. The combined stress significantly reduced root viability, photosynthetic pigment content, and net photosynthetic rate (Pn) while markedly increasing reactive oxygen species (ROS) levels, thiobarbituric acid-reactive substances (TBARS) content, and electrolyte leakage (EL). The seedlings exhibited pronounced wilting symptoms, along with markedly reduced root surface area and volume. Dopamine treatment significantly alleviated combined stress-induced damage. This mitigation was manifested through substantially enhanced root viability, photosynthetic pigment content, Pn, antioxidant enzyme activities, and osmotic adjustment substances concomitantly with marked reductions in ROS, TBARS content, and EL. Dopamine significantly reduced seedling wilting severity and improved root morphological parameters. This study demonstrates that dopamine enhances loquat seedlings’ tolerance to combined stress through coordinated mechanisms: maintaining photosynthetic pigments and improving stomatal conductance to sustain photosynthetic efficiency, enhancing antioxidant enzyme activity and ROS scavenging capacity to mitigate oxidative damage, and promoting osmotic solute accumulation for osmotic potential regulation. Full article

Drought stress caused by continuous global warming poses a severe challenge to the growth and development of Nitraria tangutorum. Abscisic acid has an important regulatory function in the process of plants responding to drought stress. This study took the N. tangutorum seedlings of Zhangye provenance 2-17-16 genealogy as the research object to explore the physiological mechanism of how different concentrations of exogenous ABA alleviate drought damage in N. tangutorum. The results showed that exogenous ABA could promote the growth and increase the leaf relative water content of N. tangutorum seedlings under drought stress. It alleviates the photosynthetic inhibition phenomenon of N. tangutorum seedlings under drought stress by regulating the photoprotective mechanism and energy distribution efficiency of photosystem II. It also alleviates the drought damage of N. tangutorum by increasing the content of osmotic-adjustment substance contents such as soluble sugar, soluble protein, proline, and starch, as well as enhancing the activity of antioxidant enzymes such as POD, SOD, and CAT. The comprehensive analysis showed that 20 μM and 30 μM ABA have the best alleviating effects on the drought damage of N. tangutorum seedlings. This study provides a theoretical basis for the restoration, propagation, and protection of N. tangutorum, and it is of great significance for maintaining the balance and stability of desert ecosystems. Full article

This study aims to investigate the regulatory effect of exogenous melatonin (MT) on the growth and development of cucumbers subjected to salt stress. Using the XinTaiMiCi material and indoor pot culture method, seven treatments were set up: control group (CK), T0 (salt treatment group, 150 mM S + 0 μM MT), T1 (150 mM S + 25 μM MT), T2 (150 mM S + 50 μM MT), T3 (150 mM S + 100 μM MT), T4 (150 mM S + 150 μM MT), and T5 (150 mM S + 200 μM MT). Changes in plant height, stem diameter, leaf area, relative chlorophyll content, antioxidant enzyme activity, reactive oxygen species content, and osmotic adjustment substance content in cucumber seeds and seedlings under different treatments were studied, and a correlation analysis of these indicators was conducted. Meanwhile, the expression of salt stress-related genes was detected in all seven treatment groups. The results showed that, compared to the CK, T0 significantly reduced the hypocotyl length, root length, hypocotyl diameter, root diameter, and fresh and dry weights of cucumber seeds; in the later stage of salt stress treatment, T0 significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) and the content of soluble protein in seeds. Additionally, T0 significantly increased the plant height, root length, stem diameter, leaf area, and fresh and dry weights of cucumber seedlings per plant; in the later stage of salt stress treatment, T0 significantly increased the activities of SOD, POD, CAT, and MDA and the content of soluble protein and chlorophyll in leaves. Compared to T0, the application of 50 μmol·L⁻¹ MT under salt stress significantly increased the plant height, stem diameter, root length, leaf area, and fresh and dry weights of cucumber seedlings per plant; significantly increased the activities of SOD, POD, and CAT; decreased the MDA activity; and significantly increased the content of soluble protein and chlorophyll. Under salt stress conditions, the exogenous application of low-concentration melatonin increased the expression levels of salt stress response genes (such as CsSOS, CsNHX, CsHSF, and CsDREB) in cucumber. The germination rate (GR), germination potential (GP), germination index (GI), plant height (PH), root length (RL), leaf area index (LAI), fresh weight (FW), dry weight (DW), soluble protein (SP), relative chlorophyll content (SPAD), POD, CAT, and SOD of cucumber seedlings exhibited significant positive correlations, whereas they were negatively correlated with MDA content. In conclusion, the application of 50 μM MT can effectively alleviate the oxidative and osmotic stress caused by a high-salt environment in cucumber, promote cucumber growth, and improve salt tolerance. 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

Ginseng growth is susceptible to environmental stresses, particularly the frequent occurrence of low temperatures and water fluctuations in spring in Northeast China, which often lead to a decline in medicinal yield and quality. This study systematically analyzed the physiological response characteristics and variation patterns of active components under dual stresses of low temperature and water. The aim was to elucidate the adaptation mechanism of ginseng to abiotic stresses, providing a theoretical basis for optimizing ginseng cultivation management practices and enhancing the quality of medicinal materials. In this study, 2-year-old and 4-year-old ginseng roots were selected as research materials. They were subjected to treatments of low soil moisture (20–30%), medium soil moisture (40–50%), and high soil moisture (60–70%). Low-temperature treatments were conducted at 0 °C for different durations (4 h, 24 h, 33 h, 48 h). Physiological indicators of the ginseng roots were determined at each time point, and the active components of ginseng roots in the control and treatment groups were investigated. The results indicated significant differences in osmotic adjustment substance changes between 2-year-old and 4-year-old ginseng roots. The content of superoxide dismutase (SOD) increased during low-temperature stress in both age groups. An increase or decrease in soil moisture significantly enhanced the accumulation of total ginsenosides. However, low-temperature stress notably reduced the accumulation of total ginsenosides. Nevertheless, after low-temperature treatment, the PPT-type ginsenosides in the high soil moisture group showed a significant increase. The findings of this study provide a scientific basis for improving the medicinal component content of ginseng and offer theoretical support for future water management practices. Full article

This study investigated the response of watermelon seedlings to drought stress by assessing the growth, physiological, and biochemical indices using a pot-based continuous drought method. Drought stress indices, phenotypic plasticity indices, and membership function values were calculated, followed by a correlation analysis, principal component analysis, and cluster analysis, to comprehensively evaluate the drought resistance of 13 watermelon genotypes. The results revealed that drought stress significantly reduced the fresh and dry weights, root length, root area, root volume, root tips, and forks of watermelon seedlings. Additionally, drought significantly reduced the relative water content of leaves and increased the levels of osmotic-adjustment substances (soluble sugars, soluble proteins, proline, and starch). Persistent drought also modulated the activities of antioxidant enzymes (SOD, POD, and CAT), leading to oxidative stress through the accumulation of H₂O₂. Membrane damage, indicated by a significant increase in the MDA content and relative conductivity, was observed, adversely affecting seedling growth. Phenotypic plasticity indices indicated that watermelon exhibits strong adaptability to drought. Cluster analysis categorized the 13 genotypes into four groups: highly drought-resistant (14X5), drought-resistant (LK13, JLR, HXF1, 14X4, 14X1, and 14X6), low drought-resistant (21F05, JH1, JR3, 14X7, and 16F02), and drought-sensitive (16C07). This study provides valuable genetic resources for breeding drought-resistant watermelon varieties. Full article

Drought threatens the stability of artificial black locust forests on the Loess Plateau, yet there is limited research on the physiological and metabolic responses of mature black locust to drought stress. This study employed a throughfall exclusion system—i.e., moderate drought (40% throughfall reduction), extreme drought (80% throughfall reduction), and 0% throughfall reduction for control—to analyze leaf microstructure, relative water content (RWC), osmotic adjustment substances, hormone levels, and flavonoid metabolites in black locust under controlled drought stress. The results demonstrated that as drought stress intensified, stomatal aperture and density decreased, while trichome density and length exhibited significant increases. MDA, proline, IAA, and osmotic adjustment substances (soluble protein, reducing sugar, and total sugar) first increased and then decreased as drought stress intensified. A total of 245 flavonoid compounds were identified through metabolomic analysis, among which 91 exhibited differential expression under drought treatments. Notably, 37 flavonoids, including flavonols and glycosylated derivatives, were consistently upregulated. These findings suggest that drought stress can lead to the accumulation of flavonoids. This study explored the physiological and metabolic responses of mature black locust trees to drought stress, offering insights for selecting drought-resistant species in vegetation restoration and informing ecological management practices in arid regions. Full article

Quinoa (Chenopodium quinoa Willd.) has been widely grown as a cash crop. However, the molecular mechanism by which it responds to cold stress at the seed germination stage is still largely unknown. In this study, we performed a comparative transcriptomic analysis between the cold-tolerant cultivar XCq and cold-sensitive cultivar QCq in response to cold stress. A total number of 4552 and 4845 differentially expressed genes (DEGs) were identified in XCq and QCq upon the treatment of cold stress, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that the mitogen-activated protein kinase (MAPK) signaling pathway was identified only among the up-regulated DEGs in XCq.The expression of DEGs, which encoding transcription factors, such as AP2/ERF, bHLH, bZIP, MYB, ICEs, and CORs related to cold response, were higher in XCq than in QCq in response to cold stress. Weighted gene co-expression network analysis (WGCNA) showed that DEGs clustered in the co-expression modules positively correlated with the factors of quinoa variety and temperature were significantly enriched in the oxidative phosphorylation metabolic pathway. Further physiochemical analyses showed that the activities of superoxide dismutase and peroxidase as well as the contents of soluble protein and sugar, were significantly higher in XCq than in QCq. In summary, MAPK signaling and oxidative metabolism were the key pathways in quinoa upon cold stress. Our findings revealed that the enhanced activities of antioxidant enzymes alleviate the lipid peroxidation of membranes and promote the accumulation of osmotic adjustment substances, thereby enabling seeds to better resist oxidative damage under cold stress. Full article

Salt stress has become a major limiting factor of rice (Oryza sativa L.) yield worldwide. Appropriate nitrogen application contributes to improvement in the salt tolerance of rice. Here, we show that improvement in nitrogen-use efficiency increases salt stress tolerance in rice. Rice varieties with different nitrogen-use efficiencies were subjected to salt stress; they were stimulated with 50, 100, and 150 mmol/L of NaCl solution at the seedling stage and subjected to salinities of 0.2, 0.4%, and 0.6% at the reproductive growth stage. Compared with nitrogen-inefficient rice varieties, the nitrogen-efficient rice varieties showed significant increases in the expression levels of nitrogen-use-efficiency-related genes (TOND1 and OsNPF6.1), nitrogen content (5.1–12.1%), and nitrogen-use enzyme activities (11.7–36.4%) when under salt stress conditions. The nitrogen-efficient rice varieties showed a better adaptation to salt stress, as shown by the decrease in leaf-withering rate (4.7–10.3%), the higher chlorophyll (3.8–9.7%) and water contents (1.1–9.2%), and the better root status (7.3–9.1%) found in the rice seedlings under salt stress conditions. Analysis of physiological indexes revealed that the nitrogen-efficient rice varieties accumulated higher osmotic adjustment substances (9.7–79.9%), lower ROS (23.1–190.8%) and Na⁺ (15.9–97.5%) contents, higher expression levels of salt stress-related genes in rice seedlings under salt stress conditions. Furthermore, the nitrogen-efficient rice varieties showed higher yield under salt stress, as shown by a lower salt-induced decrease in 1000-grain weight (2.1–6.2%), harvest index (1.4–4.9%), and grain yield (2.8–4.1%) at the reproductive growth stage in salinized soil. Conversely, the nitrogen-efficient rice varieties showed better growth and physiological metabolism statuses under severe salt stress conditions. Our results suggest that nitrogen-efficient rice varieties could improve nitrogen-use and transport efficiency; accordingly, their use can improve the gene expression network, alleviating salt damage and improving grain yield under severe salt stress conditions. Full article

Phosphorus application is widely regarded as a key measure for improving crop resistance to drought. This study investigated the effect of appropriate phosphorus fertilization on photosynthesis, physiological traits, and yield under water stress during the soybean flowering stage and selected the drought-sensitive soybean variety “Sui Nong 26” as the pot experiment object under a completely randomized design. The experiment was designed with three irrigation lower limits, corresponding to 70%, 60%, and 50% of the field capacity (FC), referred to as T1, T2, and T3. Four phosphorus fertilizer applications were also included: 0, 40, 50, and 60 mg·kg (designated as P0, P1, P2, and P3), resulting in a total of 12 treatments. Photosynthetic parameters, antioxidant enzyme activities, membrane lipid peroxidation, osmotic adjustment substances, yield, and yield components were measured to assess the effects of phosphorus fertilization on drought resistance. Results showed that under water stress, moderate phosphorus application (P1 and P2) enhanced photosynthetic capacity, antioxidation, osmotic adjustment, and yield, particularly by scavenging excess reactive oxygen species, protecting cells from oxidative damage, and maintaining metabolic balance, leading to increased yield. The average net photosynthetic rate and yield per plant under P1 and P2 levels increased by 33.53% and 37.67%, and 20.7% and 15.6%, respectively, compared to P0. In contrast, excessive phosphorus application (P3) improved the above parameters but had a significantly lower effect than moderate phosphorus application. Thus, appropriate phosphorus application is crucial for soybeans under water stress. Moderate application not only alleviates drought stress but also boosts soybean yield. This study highlights the importance of appropriate phosphorus use for mitigating water stress, offering scientific evidence for its practical application in agriculture. At the same time, with the increasing severity of climate change and water scarcity, phosphorus fertilizer application strategies under varying water conditions provide critical support for the application of precision agriculture technologies and ensuring food security. Full article

This study investigated the seasonal variations in photosynthetic characteristics and adaptation mechanisms of the endangered Acer miaotaiense subsp. yangjuechi Fang et P. L. Chiu under different shading treatments, offering theoretical insights and technical support for its relocation and conservation strategies. Five shading intensity treatments were established: full light (CK), 30% (T1), 50% (T2), 70% (T3), and 90% (T4). The growth and physiological conditions of 5-year-old A. miaotaiense subsp. yangjuechi seedlings were monitored across seasons. The findings revealed that plants grown under 70% shade had the best growth performance and leaf morphological indices. In summer, the levels of osmotic adjustment substances and peroxidase activity were the highest, whereas malondialdehyde (MDA) levels increased progressively throughout the season. Notably, superoxide dismutase activity exhibited an opposite trend to MDA. Proline and MDA contents were the highest under full light conditions and lowest under 70% shade, whereas soluble sugars and starch showed the reverse pattern. Chlorophyll content and photosystem II efficiency peaked under 70% shade, with the highest net photosynthetic rate and light saturation point observed in the 70% and 90% shade treatments. A comprehensive evaluation suggests that 70% shade is more conducive to the normal growth and development of A. miaotaiense subsp. yangjuechi seedlings. Full article