Root Stress Research Articles

Integration of Genetic and Imaging Data to Detect QTL for Root Traits in Interspecific Soybean Populations

Wild soybean, which has many desirable traits, such as adaptability to climate change-related stresses, is a valuable resource for expanding the narrow genetic diversity of cultivated soybeans. Plants require roots to adapt to different environments and optimize water and nutrient uptake to support growth and facilitate the storage of metabolites; however, it is challenging and costly to evaluate root traits under field conditions. Previous studies of quantitative trait loci (QTL) have been mainly based on cultivated soybean populations. In this study, an interspecific mapping population from a cross between wild soybean ‘PI483463’ and cultivar ‘Hutcheson’ was used to investigate QTLs associated with root traits using image data. Our results showed that 39 putative QTLs were distributed across 10 chromosomes (chr.). Seventeen of these were clustered in regions on chr. 8, 14, 15, 16, and 17, accounting for 19.92% of the phenotypic variation. We identified five significant QTL clusters influencing root-related traits, such as total root length, surface area, lateral total length, and number of tips, across five chr., with favorable alleles from both wild and cultivated soybeans. Furthermore, we identified eight candidate genes controlling these traits based on functional annotation. These genes were highly expressed in root tissues and directly or indirectly affected soybean root growth, development, and stress responses. Our results provide valuable insights for breeders aiming to optimize soybean root traits and leveraging genetic diversity from wild soybean species to develop varieties with improved root morphological traits, ultimately enhancing overall plant growth, productivity, and resilience.

Effect of Axial Modification on the Meshing Performance of Involute Beveloid Gear Pair

In order to enhance the load-bearing capacity of the involute beveloid gear pair, this study proposes research on improving the contact stress through axial modification. Under the condition of segmented parabolic axial modification, the mathematical equation for the tooth flank of the beveloid gear is derived. A simulation meshing model for the beveloid gear pair is constructed to investigate the effects of different amounts and lengths of axial modification on the meshing performance, changes in flank and root stress, and transmission error before and after modification. The results indicate that as the modification amount increases, the maximum equivalent stress initially decreases and then exhibits a tendency towards stability. Moreover, an increase in modification length concentrates the contact zone towards the middle of the tooth flank while expanding the range of tooth root stress distribution, and it also leads to a decrease in maximum equivalent stress. The implementation of the modification has been observed to result in a reduction in cumulative transmission error and an effective reduction in edge load on the beveloid gear pair, which has been demonstrated to enhance the bearing capacity and transmission stability extension while also impacting the dynamic meshing performance.

Flow environment affects nutrient transport in soft plant roots.

This work estimates Michaelis-Menten kinetics parameters for nutrient transport under varying flow rates in the soft roots of Indian mustard (Brassica juncea) using a plant fluidic device. To find the metallic components within the roots, inductively coupled plasma mass spectrometry (ICP-MS) analysis was performed. The flow rate-dependent metabolic changes were examined using Raman spectral analysis. In addition, three-dimensional numerical simulations were conducted to assess mechanical stresses resulting from the concentration difference that enhances osmotic pressure and flow loading at the root-liquid interface. Convection, the primary mode of nutrient transport in flowing media, was observed to reduce nutrient uptake at higher flow rates. In contrast, diffusion became more prevalent in areas where the complex root structure restricted the flow field. The concentration gradient between the upstream and downstream regions of the root caused nutrient diffusion from downstream to upstream. As seen, an increase in flow rate resulted in a decrease in root length due to the reduction of advantageous metabolites, which led to lower average mechanical stress and osmotic pressure loading. Additionally, osmotic pressure at the root-liquid interface was found to increase over time. Numerical simulations revealed that the average internal mechanical stress was substantially greater when osmotic pressure was considered. This emphasizes the importance of accounting for osmotic pressure when assessing mechanical stress in roots. This study uses a fluidic device that replicates hydroponic conditions for the first time in order to evaluate the convection-dependent Michaelis-Menten kinetics of nutrient uptake in plant roots.

Pearl Millet Cover Crop Extract Inhibits the Development of the Weed Ipomoea grandifolia by Inducing Oxidative Stress in Primary Roots and Affecting Photosynthesis Efficiency.

The cover crop Pennisetum glaucum (L.) R.Br. (pearl millet) reduces the emergence of weed species in the field through a mechanism that is not fully known. The identification of the allelopathic activity of pearl millet can contribute to the development of no-tillage techniques to produce crops without or with low doses of herbicides. This issue was investigated by testing the effects of extracts from the aerial parts of pearl millet on the germination and growth of the weeds Bidens pilosa L., Euphorbia heterophylla L., and Ipomoea grandifolia (Dammer) O'Donell under laboratory conditions. The ethyl acetate fraction (EAF) at a concentration of 2000 µg mL-1 was inactive on Bidens pilosa; it inhibited root length (-72%) and seedling fresh weight (-41%) of E. heterophylla, and in I. grandifolia the length of primary root and aerial parts and the fresh and dry weight of seedlings were reduced by 63%, 32%, 25%, and 12%, respectively. In roots of I. grandifolia seedlings, at the initial development stage, EAF induced oxidative stress and increased electrolyte leakage. At the juvenile vegetative stage, a lower concentration of EAF (250 µg mL-1) induced a stimulus in seedling growth (+60% in root length and +23% in aerial parts length) that was associated with increased photosynthetic efficiency. However, at higher concentrations (1000 µg mL-1), it induced the opposite effects, inhibiting the growth of root (-41%) and aerial parts (-25%), with reduced superoxide dismutase activity and photosynthetic efficiency. The stilbenoid pallidol was identified as the main compound in EAF. The allelopathic activity of pearl millet may be attributed, at least in part, to the impairment of energy metabolism and the induction of oxidative stress in weed seedlings, with pallidol possibly involved in this action. Such findings demonstrated that the application of the EAF extract from pearl millet can be a natural and renewable alternative tool for weed control.

The basal level of salicylic acid represses the PRT6 N-degron pathway to modulate root growth and stress response in rice.

Maintaining a stable basal level of salicylic acid (SA) is crucial for plant growth, development, and stress response, though basal levels of SA vary significantly among plant species. However, the molecular mechanisms by which basal SA regulates plant growth and stress response remain to be elucidated. In this study, we performed a genetic screen to identify suppressors of the root growth defect in Osaim1, a rice mutant deficient in basal SA biosynthesis. We found that mutation in the E3 ligase OsPRT6, a key component of the Arg/N-degron pathway, rescued the root growth defect of Osaim1. Further analysis revealed that OsWRKY62 and OsWRKY76 act as substrates of the OsPRT6 N-degron pathway to modulate root growth. We demonstrated that reducing the basal SA levels activate the PRT6 N-degron pathway. Additionally, we found that basal SA modulates stress response partially through the PRT6 N-degron pathway. Importantly, the effects of basal SA levels on PRT6 N-degron pathway are conserved in plants. Taken together, these findings uncover a novel regulatory mechanism in which the basal SA represses the PRT6 N-degron pathway to modulate root growth and abiotic stress response in rice.

Function of Nodulation-Associated GmNARK Kinase in Soybean Alkali Tolerance.

Soybean (Glycine max) is a vital crop that is rich in high-quality protein and edible oil for human nutrition and agriculture. Saline-alkali stress, a severe environmental challenge, significantly limits soybean productivity. In this study, we found that the nodule receptor kinase GmNARK enhances soybean tolerance to alkali stress besides nodulation. GmNARK could be induced by alkali stress in soybean roots. Ectopic overexpression of the GmNARK gene in Arabidopsis could significantly improve plant tolerance to alkaline stress. Moreover, overexpression or silencing of the GmNARK gene in soybean hairy roots also enhanced composite soybean plant tolerance to alkaline stress on plates and in soils. Additionally, overexpression of the GmNARK gene upregulated expression levels of the genes that are involved in the reactive oxygen species (ROS) signaling pathways. These findings provide a critical theoretical basis for further elucidating the role of GmNARK kinase in salt-alkali resistance and lay a foundation for improving soybean productivity under salt-alkali stress.

Measurement of localized dynamic gear meshing forces based on distributed root stress

Measurement of localized dynamic gear meshing forces based on distributed root stress

Identification and Characterization of Key Genes for Nitrogen Utilization from Saccharum spontaneum Sub-Genome in Modern Sugarcane Cultivar.

Sugarcane (Saccharum spp.) is globally considered an important crop for sugar and biofuel production. During sugarcane production, the heavy reliance on chemical nitrogen fertilizer has resulted in low nitrogen use efficiency (NUE) and high loss. Up until now, there has been extensive research on the transcriptomic dynamics during sugarcane response to low nitrogen (LN) stress. However, the specific contribution of S. spontaneum to the NUE of modern sugarcane remains unclear. In the present study, the comparative transcriptome analysis of two contrasting sugarcane cultivars in response to nitrogen deficiency was performed via the combination of genomes of S. spontaneum and S. officinarum. Sub-genome analysis indicated that S. spontaneum supports the high NUE of modern sugarcane by providing genes related to nitrogen and carbohydrate metabolism, photosynthesis, and amino acid metabolism. Additionally, the key genes involved in nitrogen metabolism from the S. spontaneum were successfully identified through weighted gene co-expression network analyses (WGCNA), and a high-affinity nitrate transporter named ScNRT2.3 was subsequently cloned. Heterogeneous expression of the ScNRT2.3, a cell membrane-localized protein, could enhance the growth of Arabidopsis under low nitrate conditions. Furthermore, a conserved protein module known as NAR2.1/NRT2.3 was shown to regulate the response to LN stress in sugarcane roots through molecular interaction. This work helps to clarify the contribution of S. spontaneum to the NUE in modern sugarcane, and the function of the ScNRT2.3 in sugarcane.

Non-Extraction Management fo a Camouflaged Class III with Mandibular Repositioning Due to Occlusal Interferences and Severe Dental Wear in an Adult Patient Using Distalization Technique with Skeletal Anchorage

Class III malocclusion results from a combination of hereditary and environmental factors and affects various populations, with higher prevalence in Asians and Hispanics. Characteristics include maxillary deficiency, mandibular prognathism, or both, often leading to a pseudo-Class III if left untreated. Traditional treatments involve extractions or interproximal reductions (IPR), but these approaches can be time-consuming and less acceptable to patients, especially in aesthetic zones. Skeletal anchorage with mini-screws offers a modern solution, enabling movements such as full arch distalization, intrusion beyond 1 mm, and multi-planar adjustments without excessive root stress. This method reduces treatment time and avoids complications like bowing effects often seen in conventional techniques. The case study describes a 30-year-old patient with Class III malocclusion, lower arch crowding, and incisor wear. Treatment involved using mini-screws for asymmetrical distalization in all quadrants. Bite blocks facilitated mandibular repositioning, and space was created to align the lower incisors without compromising periodontal health. The treatment took 16 months, including temporary incisal reconstructions and final restoration with lithium disilicate veneers. The patient’s malocclusion, mandibular deviation, and tooth wear were successfully addressed. The skeletal anchorage allowed precise control over movements, maintaining facial height and achieving stable occlusion. Condylar repositioning eliminated zigzag deviation and discomfort. Compared to traditional methods, this approach was faster and tailored to the patient’s needs, avoiding extractions while improving aesthetics and function. Skeletal anchorage proves effective in addressing challenges that traditional orthodontics cannot resolve, offering faster treatment times, better control in all three spatial planes, and improved patient satisfaction. This technique represents a significant advancement in orthodontic care for complex cases.

Comparative analysis of the LEA gene family in seven Ipomoea species, focuses on sweet potato (Ipomoea batatas L.)

Late Embryogenesis Abundant (LEA) proteins are extensively distributed among higher plants and are crucial for regulating growth, development, and abiotic stress resistance. However, comprehensive data regarding the LEA gene family in Ipomoea species remains limited. In this study, we conducted a genome-wide comparative analysis across seven Ipomoea species, including sweet potato (I. batatas), I. trifida, I. triloba, I. nil, I. purpurea, I. cairica, and I. aquatica, identifying 73, 64, 77, 62, 70, 70, and 74 LEA genes, respectively. The LEA genes were divided into eight subgroups: LEA_1, LEA_2, LEA_3, LEA_4, LEA_5, LEA_6, SMP, and Dehydrin according to the classification of the LEA family in Arabidopsis. Gene structure and protein motif analyses revealed that genes within the same phylogenetic group exhibited comparable exon/intron structures and motif patterns. The distribution of LEA genes across chromosomes varied among the different Ipomoea species. Duplication analysis indicated that segmental and tandem duplications significantly contributed to the expansion of the LEA gene family, with segmental duplications being the predominant mechanism. The analysis of the non-synonymous (Ka) to synonymous (Ks) ratio (Ka/Ks) indicated that the duplicated Ipomoea LEA genes predominantly underwent purifying selection. Extensive cis-regulatory elements associated with stress responses were identified in the promoters of LEA genes. Expression analysis revealed that the LEA gene exhibited widespread expression across diverse tissues and showed responsive modulation to various abiotic stressors. Furthermore, we selected 15 LEA genes from sweet potatoes for RT-qPCR analysis, demonstrating that five genes responded to salt stress in roots, while three genes were responsive to drought stress in leaves. Additionally, expression changes of seven genes varied at different stages of sweet potato tuber development. These findings enhanced our understanding of the evolutionary dynamics of LEA genes within the Ipomoea genome and may inform future molecular breeding strategies for sweet potatoes.

Melatonin Enhances the Low-Calcium Stress Tolerance by Regulating Brassinosteroids and Auxin Signals in Wax Gourd.

In plants, calcium (Ca) serves as an essential nutrient and signaling molecule. Melatonin is a biologically active and multi-functional hormone that plays an important role in improving nutrient use efficiency. However, its involvement in plant responses to Ca deficiency remains largely unexplored. This study aimed to assess the effects of melatonin on Ca absorption, the antioxidant system, and root morphology under low-Ca (LCa) stress conditions, as well as to identify key regulatory factors and signaling pathways involved in these processes using transcriptome analysis. Under LCa conditions, wax gourd seedling exhibited significant decreases in Ca accumulation, showed inhibition of root growth, and demonstrated the occurrence of oxidative damage. However, melatonin application significantly enhanced Ca content in wax gourd seedlings, and it enhanced the absorption of Ca2+ in roots by upregulating Ca2+ channels and transport genes, including BhiCNGC17, BhiCNGC20, BhiECA1, BhiACA1, and BhiCAX1. Furthermore, the application of exogenous melatonin mitigated the root growth inhibition and oxidative damage caused by LCa stress. This was evidenced by increases in the root branch numbers, root tips, root surface area, and root volume, as well as enhanced root vitality and antioxidant enzyme activities, as well as decreases in the reactive oxygen species content in melatonin treated plants. Transcriptome results revealed that melatonin mainly modulated the brassinosteroids (BRs) and auxin signaling pathway, which play essential roles in root differentiation, elongation, and stress adaptation. Specifically, melatonin increased the active BR levels by upregulating BR6ox (a BR biosynthesis gene) and downregulating BAS1 (BR degradation genes), thereby affecting the BR signaling pathway. Additionally, melatonin reduced IAA levels but activated the auxin signaling pathway, indicating that melatonin could directly stimulate the auxin signaling pathway via an IAA-independent mechanism. This study provides new insights into the role of melatonin in nutrient stress adaptation, offering a promising and sustainable approach to improve nutrient use efficiency in wax gourd and other crops.

Study on the parameters of steel plate reinforcement rib-deck crack considering local stress disturbances

Local reinforcement will change the local stiffness distribution of the component, causing perturbation effects on the local stress of the fatigue detail. Only considering the reinforcement effect may lead to excessive strengthening and induce new fatigue-prone points. For the fatigue detail of the rib-deck weld, steel plate reinforcement test and numerical simulations were conducted. The stress changes of the deck weld toe and weld root before and after reinforcement were analyzed. The influence of parameters such as steel plate length, thickness, and width on the reinforcement effect of the weld toe crack and local stress disturbance was discussed, and reasonable parameters were recommended. The results show that after the cracking of the weld toe, the stress concentration locations at the weld toe and weld root of the deck shift from the center of the specimen to the crack tip. Steel plate reinforcement can effectively restrain the crack propagation, but can lead to an increase in the stress at the deck weld root within the reinforced area. A good reinforcement effect can be achieved while the steel plate covers the crack, and further increasing the steel plate length has limited improvement on the reinforcement effect but reduces the adverse effect of steel plate reinforcement on the stress of the deck weld root. Increasing the steel plate width will increase the adverse effect of steel plate reinforcement on the deck weld root stress, and it is recommended to use steel plates with a length greater than 120 mm and a length-to-width ratio greater than 4 for reinforcement. Increasing the width of the steel plate has a relatively small effect on the reinforcement effect and the stress at the deck weld root, and steel plates with the same thickness as the deck are recommended.

Unravelling the role of Black Soldier Fly Frass (BSFF) in nutrient enrichment and growth promotion of groundnut (Arachis hypogaea L.)

The decomposition of organic waste by Black Soldier Fly (BSF) plays a potential role in plant growth promotion and soil nutrient enrichment. This study investigated the effect of different compost from food waste, vegetable & fruit waste, cow manure, pig manure, poultry manure, TNPL (Tamil Nadu Newsprint and Papers Limited) bio sludge and combinations of these materials induced varied growth promotion on groundnut. A pot culture experiment evaluated shoot length, root length, germination percentage, plant biomass and vigour index. The best results were observed in the treatment combining hostel food waste and vegetable waste (50 %) with poultry manure (50 %) (T7), showing a shoot length of 20.34 cm, vigour index of 3629, plant biomass of 24.3 g, and germination percentage of 93.33%. Other treatments, such as food waste (T1) and vegetable and fruit waste (T2), showed vigour indices of 2561.6 and 2692.9, respectively, while the untreated control had the lowest vigour index of 900.4. Nutrient analysis of T7 compost revealed high levels of nitrogen (462 kg/ha), phosphorus (375 kg/ha), potassium (320 kg/ha) and micronutrients like iron (29.04 ppm) and zinc (7.58 ppm). GC-MS analysis identified growth-promoting compounds like Cyclohexanol (64.3 %), Glycerol (3.9 %) and Dibutyl phthalate (1.49 %). Metabolite set enrichment analysis (MSEA) highlighted pathways like fatty acid biosynthesis and glycerolipid metabolism, which support root development and stress tolerance. The results indicated that BSF compost, especially from food and vegetable waste with poultry manure, significantly enhances soil fertility and plant growth, providing a sustainable solution for organic waste management.

Overexpression of the tomato pathogenesis-related gene SlPR-1.9 confers increased tolerance to salt stress in Arabidopsis thaliana

Pathogenesis-related (PR) proteins are essential components of plant defense mechanisms, responding to both biotic and abiotic stresses. Among these, PR-1 proteins feature a CAP (Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-related 1) domain, which is crucial for immune responses and pathogen defense due to its ability to stabilize protein structures and interact with various molecules. This study investigated the role of the tomato PR-1 gene SlPR-1.9 in enhancing salt tolerance in Arabidopsis thaliana. The gene’s coding sequence was cloned and transferred into Arabidopsis to create SlPR-1.9 overexpression lines. These transgenic lines, alongside wild-type plants, were exposed to salt stress (150 mM NaCl) to assess their tolerance. Morphological analysis revealed that the transgenic lines demonstrated greater resilience to salt stress compared to wild-type plants, with less severe leaf curling and color changes. Additionally, lower proline accumulation, a stress marker, in the transgenic lines indicated an enhanced adaptive response. Bioinformatics analysis of the protein encoded by SlPR-1.9, A0A3Q7HSC4, suggested a strong interaction with galactolipase. Expression analysis showed that SlPR-1.9 was mainly expressed in roots and during early fruit development, suggesting a significant role in root physiology and stress response. These findings indicate that overexpression of SlPR-1.9 can improve plant tolerance to salt stress, offering potential applications for enhancing crop resilience to environmental challenges.

ABA-activated low-nanomolar Ca2+-CPK signalling controls root cap cycle plasticity and stress adaptation.

Abscisic acid (ABA) regulates plant stress adaptation, growth and reproduction. Despite extensive ABA-Ca2+ signalling links, imaging ABA-induced increases in Ca2+ concentration has been challenging, except in guard cells. Here we visualize ABA-triggered [Ca2+] dynamics in diverse organs and cell types of Arabidopsis thaliana using a genetically encoded Ca2+ ratiometric sensor with a low-nanomolar Ca2+-binding affinity and a large dynamic range. The subcellular-targeted Ca2+ ratiometric sensor reveals time-resolved and unique spatiotemporal Ca2+ signatures from the initial plasma-membrane nanodomain, to cytosol, to nuclear oscillation. Via receptors and sucrose-non-fermenting1-related protein kinases (SnRK2.2/2.3/2.6), ABA activates low-nanomolar Ca2+ transient and Ca2+-sensor protein kinase (CPK10/30/32) signalling in the root cap cycle from stem cells to cell detachment. Surprisingly, unlike the prevailing NaCl-stimulated micromolar Ca2+ spike, salt stress induces a low-nanomolar Ca2+ transient through ABA signalling, repressing key transcription factors that dictate cell fate and enzymes that are crucial to root cap maturation and slough. Our findings uncover ABA-Ca2+-CPK signalling that modulates root cap cycle plasticity in adaptation to adverse environments.

Chemical Composition, Physiological and Morphological Variations in Salvia subg. Perovskia Populations in Response to Different Salinity Levels.

This study evaluated the salinity tolerance of five populations of Salvia subg. Perovskia (S. abrotanoides and S. yadngii). The aims of the study were to assess essential oil components, as well as growth and physiological parameters of two Salvia species in response to salt stress. Four different levels of salinity (0, 60, 90, and 120 mM NaCl) were applied. The effects of various concentrations of NaCl on essential oil content, composition, growth, water relation, proline, lipid peroxidation (MDA), hydrogen peroxide content, and antioxidant enzyme activity, as well as Na and K contents in leaves and the roots were evaluated. The results revealed that root dry weight loss was higher than that of shoots, indicating root vulnerability due to direct exposure to the salt stress. The lowest and highest oil content was obtained in PATKH (0.6%) at 60 mM and PABAD (0.6%) in 90 mM to 2.16% in PABSM population under 120 mM NaCl. Based on GC-MS analysis, 1,8-cineol (11.64 to 22.02%), camphor (2.67 to 27.14%), bornyl acetate (2.12 to 11.07%), borneol (2.38 to 24.37%), β-caryophyllene (3.24 to 7.58%), α-humulene (2.97 to 7.92%), and δ-3-carene (5.31 to 26.65%) were the most abundant compounds. Based on the principal component analysis (PCA), the most salinity-tolerant populations belonged to P. abrotanoides species. These populations are characterized by high root stress tolerance index (STI), root elements, and relative water content (RWC) with elevated levels of salinity stress. Finally, the findings might be useful in unraveling the salinity tolerance mechanisms for integrating stress tolerance with medicinal qualities in future studies.

Biostimulants for sustainable agriculture in forage crops

Biostimulants, a promising avenue in agriculture, are substances that significantly enhance plant growth and productivity. They are a rich source of various compounds and microorganisms, including humic substances, amino acids, seaweed extracts, chitin and chitosan polymers, inorganic compounds, seed and root extracts, and organic wastes. Humic substances derived from decomposed organic matter are crucial in improving soil structure and nutrient availability. On the other hand, amino acids and protein hydrolysates promote nitrogen uptake and stress resistance, enhancing plant growth. The rich in polysaccharides and phytohormones, seaweed extracts enhance root development and stress tolerance. Polymers such as chitin and chitosan, derived from crustaceans and fungi, provide protective effects against pathogens and environmental stressors. Inorganic compounds and plant extracts also contribute to growth and resistance. The growing global biostimulants market is a testament to the increasing demand for environmentally friendly agricultural solutions, highlighting the urgency of adopting these solutions. Unlike traditional fertilizers, biostimulants do not directly provide nutrients but improve how plants use available nutrients more efficiently. Research underscores the potential of biostimulants to contribute to sustainable agriculture by increasing yield, quality, and disease resistance. Indispensable in modern agriculture, biostimulants are the key to creating sustainable and productive agricultural systems with more resilient plants by stimulating the development of crops, especially under unfavorable conditions, and improving crop quality.

Osmotic stress in roots drives lipoxygenase-dependent plastid remodeling through singlet oxygen production.

Osmotic stress, caused by the lack of water or by high salinity, is a common problem in plant roots. Osmotic stress can be reproducibly simulated with the application of solutions of the high-molecular-weight and impermeable polyethylene glycol. The accumulation of different reactive oxygen species, such as singlet oxygen, superoxide, and hydrogen peroxide, accompany this stress. Among them, singlet oxygen, produced as a byproduct of lipoxygenase activity, has been associated with limiting root growth. To better understand the source and effect of singlet oxygen, we followed its production at the cellular level in Arabidopsis (Arabidopsis thaliana). Osmotic stress initiated profound changes in plastid and vacuole structure. Confocal and electron microscopy showed that the plastids were a source of singlet oxygen accompanied by the appearance of multiple, small extraplastidic bodies that were also an intense source of singlet oxygen. A marker protein, CRUMPLED LEAF, indicated that these small bodies originated from the plastid outer membrane. Remarkably, LINOLEATE 9S-LIPOXYGENASE 5 (LOX5) was shown to change its distribution from uniformly cytoplasmic to a more clumped distribution together with plastids and the small bodies. In addition, oxylipin products of Type 9 lipoxygenase increased, while products of Type 13 lipoxygenases decreased. Inhibition of lipoxygenase by the salicylhydroxamic acid inhibitor or in downregulated lipoxygenase lines prevented cells from initiating the cellular responses, leading to cell death. In contrast, singlet oxygen scavenging halted terminal cell death. These findings underscore the reversible nature of osmotic stress-induced changes, emphasizing the pivotal roles of lipoxygenases and singlet oxygen in root stress physiology.

Novel application of cyclo(-Phe-Pro) in mitigating aluminum toxicity through oxidative stress alleviation in wheat roots

Microbial secondary metabolites are crucial in plant-microorganism interactions, regulating plant growth and stress responses. In this study, we found that cyclo(-Phe-Pro), a proline-based cyclic dipeptide secreted by many microorganisms, alleviated aluminum toxicity in wheat roots by increasing root growth, decreasing callose deposition, and decreasing Al accumulation. Cyclo(-Phe-Pro) also significantly reduced Al-induced reactive oxygen species (ROS) with H2O2, O2•-, and •OH levels decreasing by 19.1%, 42.8%, and 17.9% in root tips, thus protecting the plasma membrane from oxidative damage. Although Al stress increased the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in wheat roots, cyclo(-Phe-Pro) application reduced these enzyme activities. However, compared to the Al treatment, cyclo(-Phe-Pro) application increased DPPH and FRAP activities by 16.8% and 14.9%, indicating increased non-enzymatic antioxidant capacity in wheat roots. We observed that Al caused the oxidation of ascorbate (AsA) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively. Under Al stress, cyclo(-Phe-Pro) treatment maintained reduced AsA and GSH levels, as well as high AsA/DHA and GSH/GSSG redox pair ratios in wheat roots. High AsA/DHA and GSH/GSSG ratios can reduce Al toxicity by neutralizing free radicals and restoring redox homeostasis via antioxidant properties. These results suggest that cyclo(-Phe-Pro) maintains ASA- and GSH-dependent redox homeostasis to alleviate oxidative and Al stress in wheat roots. Findings of this study establishes a theoretical foundation for using microbial metabolites to mitigate Al toxicity in acidic soils, highlighting their potential in sustainable agriculture.

Response and Reliability of Composite Post Insulators Under Random Earthquake

Abstract This article examines the stochastic response and seismic reliability of composite post-insulators under random seismic excitation. A random seismic motion model, tailored for power facility seismic research in China and compliant with the “Seismic Design Specification for Power Facilities” (GB50260-2013), is developed. This model accounts for both amplitude and frequency non-stationary. A nonlinear dynamic model for composite post insulators is then established, incorporating the nonlinearity at the multi-section insulator and flange connections. Numerical methods are employed for random seismic response analysis to address the non-stationary nature of seismic motion. The proposed model’s validity is confirmed by comparing it with the vibration table test results. Finally, the seismic reliability of composite post insulators, with root stress as the control criterion, is assessed using the probability density evolution method.