Plant Growth Responses Research Articles

Effects of Nitrogen Fertilizer Rate with Urease and Nitrification Inhibitors on Certain Morphological Traits and Quality of Sugarcane (Saccharum officinarum L.)

In this study, we investigated the effects of the N fertilizer rates (commonly applied by farmers compared to rate based on soil analysis) with an appropriate N fertilizer rate associated with urease inhibitors (UIs), nitrification inhibitors (NIs) and their combinations (UINIs) on sugarcane (Saccharum officinarum L.) growth, morphological traits, and quality. The treatments consisted of 2 UIs (N-(n-butyl) thiophosphoric triamide (NBPT) and garlic (Allium sativum L.)) and 3 NIs (dimethylpyrazole phosphate (DMPP), ground neem seed (Azadirachta indica A. Juss. var. siamensis Valeton) and praxelis (Praxelis clematidea (Griseb.) R.M. King & H. Rob)). The results showed that increasing the N fertilizer rate encouraged sugarcane growth by up to 4.5% and increased N content by 16.2% in the cane yield. Adding inhibitors produced positive responses in plant growth and yield, possibly due to prolonging N fertilizer in the soil and extending the supply of N to the plant. Compared to biological inhibitors, the synthetic inhibitors resulted in longer stalk lengths but lower stalk diameters. The inhibitor treatments significantly enhanced the aboveground biomass and N content in plants by up to 41.5 and 41.9%, respectively, compared to only fertilizer. The inhibitor treatments in commercial cane sugar (CCS) increased by up to 13.6%. However, decreasing the N fertilizer rate with addition of inhibitors assisted in keeping mineral N in the soil, which further enhanced N uptake and led to improved plant growth and yield. Added DMPP showed the potential to slow down N loss from soil, which enhanced rapid growth and resulted in higher aboveground biomass.

Genetic Analysis of the Peach SnRK1β3 Subunit and Its Function in Transgenic Tomato Plants

Background/Objectives: The sucrose non-fermentation-related kinase 1 (SnRK1) protein complex in plants plays an important role in energy metabolism, anabolism, growth, and stress resistance. SnRK1 is a heterotrimeric complex. The SnRK1 complex is mainly composed of α, β, βγ, and γ subunits. Studies on plant SnRK1 have primarily focused on the functional α subunit, with the β regulatory subunit remaining relatively unexplored. The present study aimed to elucidate the evolutionary relationship, structural prediction, and interaction with the core α subunit of peach SnRK1β3 (PpSnRK1) subunit. Methods: Bioinformatics analysis of PpSnRK1 was performed through software and website. We produced transgenic tomato plants overexpressing PpSnRK1 (OEPpSnRK1). Transcriptome analysis was performed on OEPpSnRK1 tomatoes. We mainly tested the growth index and drought resistance of transgenic tomato plants. Results: The results showed that PpSnRK1 has a 354 bp encoded protein sequence (cds), which is mainly located in the nucleus and cell membrane. Phylogenetic tree analysis showed that PpSnRK1β3 has similar domains to other woody plants. Transcriptome analysis of OEPpSnRK1β3 showed that PpSnRK1β3 is widely involved in biosynthetic and metabolic processes. Functional analyses of these transgenic plants revealed prolonged growth periods, enhanced growth potential, improved photosynthetic activity, and superior drought stress tolerance. Conclusions: The study findings provide insight into the function of the PpSnRK1 subunit and its potential role in regulating plant growth and drought responses. This comprehensive analysis of PpSnRK1 will contribute to further enhancing our understanding of the plant SnRK1 protein complex.

Growth and biomass-allocation responses of arabica coffee young plants subjected to the interactive effects of root deformation and light availability

Growth and biomass-allocation responses of arabica coffee young plants subjected to the interactive effects of root deformation and light availability

Salt stress-induced polyamine biosynthesis contributes to blast resistance in rice

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is a destructive disease that affects rice (Oryzae sativa L.) on a global scale. Polyamines (PAs) play diverse roles in plant growth and development and responses to biotic and abiotic stimuli. Putrescine (PUT), spermidine (SPD), and spermine (SPM) are the primary forms of polyamines (PAs). In this study, we observed that the accumulation of apoplastic PAs significantly increased in rice plants after treatment with salt or M. oryzae. The salt-treated plants exhibited enhanced resistance to rice blast disease. RNA sequencing data indicate that S-adenosylmethionine decarboxylase (SAMDC), a key enzyme involved in the synthesis of polyamines, plays a significant role in enhancing plant resistance. Overexpression of rice SAMDC (OsSAMDC) led to a significant decrease of pathogen infection in the transgenic rice plants. Additionally, OsSAMDC overexpression plants accumulated polyamines in the cytosol and apoplast, particularly SPD and SPM. Conversely, the disease resistance and accumulation of PAs were reduced in OsSAMDC-silenced plants. Exogenous application of PAs inhibited the mycelium growth, spore germination, germ tube elongation, and appressorium formation in M. oryzae. These results demonstrated that OsSAMDC-mediated polyamine biosynthesis, especially SPD and SPM, plays an essential role in rice plants to resist biotic and abiotic stresses.

Identification of the FBN gene family in tomato and functional analysis of SlFBN11 in the electron transport under low night temperature

FBNs are lipid-associated proteins that play a critical role in plant growth and stress response. However, the mechanisms of how FBNs proteins participate in the low night temperature response in tomato still unclear. Here we conducted a comprehensive genome-wide analysis of the FBN gene family in Solanum lycopersicum. In total, 14 SlFBN genes were identified, and information on their gene structures, protein motifs, phylogenetic relationships, and stress-related cis-regulatory elements (CREs) was provided. Among these, SlFBN11 was selected as a promising candidate for further functional characterization. The silencing of SlFBN11 destroys the redox balance of the PSI reaction center under low night temperature (LNT) stress, which led to increased ROS accumulation. Surprisingly, we found that the silencing of SlFNR2 also displayed an imbalance in electron transport of the PSI under LNT stress. Further experiments showed SlFBN11 can interact with SlFNR2 to positively response electron transport low night temperature. Collectively, the study provides a comprehensive analysis of the FBN genes family in Solanum lycopersicum and provides a theoretical basis for our understanding of the function of FBN genes in adaptation to LNT stresses.

Genome-wide identification and expression analysis of the GT8 gene family in tomato(Solanum lycopersicum) and the functional of SlGolS1 under cold stress

Glycosyltransferases (GTs) are a diverse superfamily of enzymes involved in glycosylation reactions, with the GT8 (glycosyltransferase 8) playing a crucial role in plant growth, development, and abiotic stress responses. Tomato, widely cultivated and is a thermophilic plant. So it is significant to study how GT8 regulates cold resistance in tomato for plant growth. In this study, we screened the whole genome of tomato by using bioinformatics methods and identified 40 members of the GT8 gene family. Analysis of cold stress transcriptome data and qRT-PCR experiments revealed the potential significance of SlGolS1 in responding to cold stress. SlGolS1 was highly expressed in the stems and flowers of tomato, with its mature protein localized in the chloroplast. Used the VIGS method to transiently silence the SlGolS1 gene, the SlGolS1-silenced plants (pTRV2-SlGolS1) rendered tomato more sensitive to cold stress compared with the control (pTRV2) tomato plant phenotype after cold treatment; enzyme activity assays showed that oxidative damage was more severe in the pTRV2-SlGolS1. In summary, SlGolS1 positively regulates cold resistance in tomato.

Comparative analysis of amino acid sequence level in plant GATA transcription factors

Transcription factors (TFs) are essential regulators of gene expression, influencing numerous biological processes such as development, growth, and cellular responses in plants. Among these, GATA TFs are distinguished by their highly conserved DNA-binding domain, characterized by a class IV zinc finger motif (CX2CX18-20CX2C). This study investigates the amino acid sequence patterns of 5,335 GATA TFs across 165 plant species sourced from the PlantTFDB database (http://planttfdb.gao-lab.org/), encompassing diverse taxonomic groups. Through comparative sequence analysis, I identify conserved domains and structural features that enhance the understanding functional roles, evolutionary conservation, and lineage-specific adaptations of GATA TFs. These findings provide valuable insights into the diversification and functional specialization of GATA TFs, with implications for improving stress tolerance and adaptability in crops. This study contributes to the broader knowledge of transcriptional regulation in plant biology.

Impact of gibberellic acid GA3, quantum dot biochar, and rhizosphere bacteria on fenugreek plant growth and stress responses under lead stress

Lead (Pb) is a stress that can cause problems with several aspects of a plant’s metabolism, potentially impeding the plant’s ability to grow and develop. The use of gibberellic acid (GA3), quantum dot biochar (QDBC), and rhizobacteria (RB) can be effective methods to overcome this problem. Gibberellic acid is a crucial plant hormone that regulates plant growth, cell division, tissue differentiation, flowering, photosynthesis, and transpiration rate. It also significantly impacts crop resilience to stress, affecting plant morphology, enzymatic activity, and physiology. Biochar, a soil supplement, enhances plant development soil health, and reduces stress effects. Due to its large surface area and porosity, it increases soil water-holding capacity, nutrient retention, and microbial activity. Quantum dots, semiconductor nanoparticles, have been proposed as a potential method to alleviate plant stress by acting as antioxidants, reducing oxidative stress, and controlling nutrient and growth regulators. Rhizobacteria, soil bacteria in plant roots, stimulate plant growth, nutrient absorption, and harvesting capacity. They produce phytohormones, increase mineral and nitrogen accessibility, and can induce systemic resistance (ISR), affecting plant defense. This study investigates the effects of combining GA3, QDBC, and RB as amendments to fenugreek, both with 500 Pb stress and without Pb stress. Treatments (control, 0.25 GA3mg/L-QDBC, 0.5 GA3mg/L-QDBC, 0.25 GA3mg/L-QDBC + RB, and 0.5 GA3mg/L-QDBC + RB) were applied in six replications using a completely randomized design. Results demonstrate that the combination of 0.5 GA3mg/L-QDBC + RB with 500 Pb stress led to significant enhancements in fenugreek shoot fresh weight (15.62%), root fresh weight (73.53%), shoot dry weight (24.00%), and root dry weight (36.53%) compared to the control. Additionally, there were notable improvements in chlorophyll a (57.23%), chlorophyll b (19.21%), and total chlorophyll (36.23%) compared to the control under Pb stress, also showing the potential of 0.5 GA3mg/L-QDBC + RB with 500 Pb stress. The study suggests that combining 0.5 GA3mg/L-QDBC + RB with 500 Pb stress can effectively mitigate Pb stress in fenugreek.

Genome-wide identification and expression analysis of the glutathione transferase gene family and its response to abiotic stress in rye (Secale cereale)

BackgroundGlutathione S-transferases (GSTs) are a crucial class of plant enzymes, playing pivotal roles in plant growth, development, and stress responses. However, studies on the functions and regulatory mechanisms of GSTs in plants remain relatively limited.ResultsThis study aimed to comprehensively identify and analyze GST proteins in rye. A total of 171 rye GST genes were identified and classified into four subfamilies, Tau, Phi, Theta, and Zeta, based on their sequence similarity and structural features. Notably, genes classified under the Tau subfamily were the most abundant at 118, while only one gene was under the Theta subfamily. Subsequent phylogenetic and collinearity analysis revealed 29 tandem duplications and 6 segmental duplication events. There were 13 collinear genes between rye and wheat, maize, and rice, demonstrating the expansion and evolution of the GST gene family. An analysis of the expression profiles of 20 representative ScGST genes in different tissues and under various environmental stresses was performed to further understand the functions and expression patterns of ScGST genes. The results showed that these genes exhibited the highest expression levels in stems, followed by fruits and leaves.ConclusionsThis study provides a comprehensive identity, classification, and analysis of rye GST genes, which offer valuable insights into the functionality and regulatory mechanisms of the GST gene family in rye. Especially, ScGST39 was identified as a candidate gene because it was significantly upregulated under multiple stress conditions, indicating its potential crucial role in plant stress tolerance mechanisms.

Utilizing the mutant library to investigate the functional characterization of GhGLR3.4 regulating jasmonic acid to defense pest infestation.

The glutamate receptor (GLR) serves as a ligand-gated ion channel that plays a vital role in plant growth, development, and stress response. Nevertheless, research on GLRs in cotton is still very limited. The present study conducted a comprehensive analysis of GLRs gene family in cotton. In total, 41 members of the GLR family were identified in cotton unveiling distinct subgroups in comparison to Arabidopsis. Among these members, the third subgroup highlights its pivotal role in cotton's defense against insect infestation. Furthermore, the CRISPR/Cas9 system was utilized to create a mutant library of GLR members, which consisted of a total of 135 independent mutant lines, resulting in the production of novel cotton materials with valuable breeding potential for pest control. Further, this study elucidates the influence of GhGLR3.4 on jasmonic acid (JA) pathway signal transduction and demonstrated its participation in the influx of intracellular Ca2+, which regulates "calcium transients" following stimulation, thereby influencing multiple intracellular reactions. The study also found that GhGLR3.4 influences the synthesis of the JA pathway and actively partakes in long-distance signal transmission among plants, facilitating the transfer of defense signals to neighbor leaves and thereby triggering systemic defense. Consequently, this research advances our knowledge of plants' comprehensive defense mechanism against insect pest infestation.

Genome expression analysis of basic helix-loop-helix transcription factors in Sea buckthorn (Hippophae rhamnoides L.).

The basic helix-loop-helix (bHLH) transcription factor family is one of the largest gene families in plants, extensively involved in plant growth, organ development, and stress responses. However, limited studies of this family are available in sea buckthorn (Hippophae rhamnoides). In this study, we identified 144 bHLH genes in H. rhamnoides (HrbHLH) through a genome-wide search method, then explored their DNA and protein sequences and physicochemical properties. According to the sequence similarities, we classified them into 15 groups with specific motif structures. To explore their expressions, we performed gene expression profiling using RNA-Seq and identified 122 HrbHLH mRNAs were highly expressed, while the remaining 22 HrbHLH genes were expressed at very low levels in all 21 samples. Among these HrbHLH genes, HrbHLH47, HrbHLH74, HrbHLH90, HrbHLH131 showed the highest expression level in the root nodule, root, leaf, stem and fruit tissues. Furthermore, eleven HrbHLH genes displayed increased expressions during the fruit development process of sea buckthorn. Finally, we validated the expression patterns of HrbHLH genes using reverse transcription quantitative real-time PCR (QPCR). This comprehensive analysis provides a useful esource that enables further investigation of the physiological roles and molecular functions of the HrbHLH TFs.

Genome-Wide Identification of GATA Family Genes in Potato and Characterization of StGATA12 in Response to Salinity and Osmotic Stress.

GATA factors are evolutionarily conserved transcription regulators that are implicated in the regulation of physiological changes under abiotic stress. Unfortunately, there are few studies investigating the potential role of GATA genes in potato plants responding to salt and osmotic stresses. The physicochemical properties, chromosomal distribution, gene duplication, evolutionary relationships and classification, conserved motifs, gene structure, interspecific collinearity relationship, and cis-regulatory elements were analyzed. Potato plants were treated with NaCl and PEG to induce salinity and osmotic stress responses. qRT-PCR was carried out to characterize the expression pattern of StGATA family genes in potato plants subjected to salinity and osmotic stress. StGATA12 loss-of-function and gain-of-function plants were established. Morphological phenotypes and growth were indicated. Photosynthetic gas exchange was suggested by the net photosynthetic rate, transpiration rate, and stomatal conductance. Physiological indicators and the corresponding genes were indicated by enzyme activity and mRNA expression of genes encoding CAT, SOD, POD, and P5CS, and contents of H2O2, MDA, and proline. The expression patterns of StGATA family genes were altered in response to salinity and osmotic stress. StGATA12 protein is located in the nucleus. StGATA12 is involved in the regulation of potato plant growth in response to salinity and osmotic stress. Overexpression of StGATA12 promoted photosynthesis, transpiration, and stomatal conductance under salinity and osmotic stress. StGATA12 overexpression induced biochemical responses of potato plants to salinity and osmotic stress by regulating the levels of H2O2, MDA, and proline and the activity of CAT, SOD, and POD. StGATA12 overexpression induced the up-regulation of StCAT, StSOD, StPOD, and StP5CS against salinity and osmotic stress. StGATA12 could reinforce the ability of potato plants to resist salinity and osmosis-induced damages, which may provide an effective strategy to engineer potato plants for better adaptability to adverse salinity and osmotic conditions.

Impact of Pristine and Aged Tire Wear Particles on Ipomoea aquatica and Rhizospheric Microbial Communities: Insights from a Long-Term Exposure Study.

Tire wear particles (TWPs), generated from tire abrasion, contribute significantly to environmental contamination. The toxicity of TWPs to organisms has raised significant concerns, yet their effects on terrestrial plants remain unclear. Here, we investigated the long-term impact of pristine and naturally aged TWPs on water spinach (Ipomoea aquatica) and its rhizospheric soil. The results indicated that natural aging reduced the toxicity of TWPs, as evidenced by decreased levels of polycyclic aromatic hydrocarbons (PAHs) in soil and TWPs themselves. Consequently, aged TWPs were found to enhance the plant growth and chlorophyll content, whereas pristine TWPs increased the plant stress. Furthermore, aged TWPs improved soil organic matter (SOM) and total organic carbon (TOC), thereby boosting the microbial enzymes involved in nitrogen cycling. Metabolomic analysis revealed that aged TWPs upregulated key pathways related to carbon and nitrogen metabolism, enhancing plant growth and stress responses. Additionally, rhizosphere bacterial diversity was higher under aged TWPs, favoring nutrient-cycling taxa such as Acidobacteriota and Nitrospirota. Pristine TWPs may lead to overproliferation of certain dominant species, thereby reducing microbial diversity in soil, which could ultimately compromise the soil health. These findings contribute to a deeper understanding of the mechanisms underlying TWP toxicity in plants and highlight the necessity for further research on the impact of aged TWPs across various plant species over different exposure durations for comprehensive risk assessment.

Genome-Wide Identification and Characterization of bHLH Gene Family in Hevea brasiliensis

The basic helix-loop-helix (bHLH) transcription factors play crucial roles in plant growth, development, and stress responses. However, their identification and insights into the understanding of their role in rubber trees remain largely uncovered. In this study, the bHLH gene family was explored and characterized in rubber trees using systematic bioinformatics approaches. In total, 180 bHLH genes were identified in the rubber tree genome, distributed unevenly across 18 chromosomes, and phylogenetic analysis classified these genes into 23 distinct subfamilies. Promoter regions revealed a high density of cis-elements responsive to light and hormones. Enrichment analysis indicated involvement in numerous biological processes, including growth, development, hormone responses, abiotic stress resistance, and secondary metabolite biosynthesis. Protein interaction network analysis identified extensive interactions between HbbHLH genes and other functional genes, forming key clusters related to iron homeostasis, plant growth, and stomatal development. Expression profiling of HbbHLH genes have demonstrated varied responses to endogenous and environmental changes. RT-qPCR of eleven HbbHLH genes in different tissues and under ethylene, jasmonic acid, and cold treatments revealed tissue-specific expression patterns and significant responses to these stimuli, highlighting the roles of these genes in hormone and cold stress responses. These findings establish a framework for exploring the molecular functions of bHLH transcription factors in rubber trees.

Increasing Phylogenetic Clustering of Arbuscular Mycorrhizal Fungal Communities in Roots Explains Enhanced Plant Growth and Phosphorus Uptake

Temporal variation during the assembly of arbuscular mycorrhizal (AM) fungal communities within plant roots have been posited as critical drivers of the plant-fungal symbiotic outcomes. However, functional implications of these dynamics for the host plant remain poorly understood. We conducted a controlled pot experiment with Sorghum bicolor to investigate how temporal shifts in AM fungal community composition and phylogenetic diversity influence plant growth and phosphorus responses to the symbiosis. We characterised the root-colonising AM fungal communities across three time points and explored their community assembly processes by analysing their phylogenetic diversity and employing joint species distribution modelling with the Hierarchical Modelling of Species Communities (HMSC) framework. We found strong AM fungal turnover through time with a high phylogenetic signal, indicating recruitment of phylogenetically clustered AM fungal species in the host. This temporal phylogenetic clustering of communities coincided with marked increases in plant biomass and phosphorus responses to the AM fungal symbiosis, suggesting that host selection for specific fungi may be a key determinant of these benefits.

Microbiome and nutrient dynamics of organic manures for precision NPK management in sunflower (Helianthus annuus L.)

AbstractOrganic manure plays an important role in soil fertility, microbial communities and sustainable agricultural strategies. In organic cultivation of crops, manures are mostly used without any calculation of the nutrients added to soil through their application. The quantities of nutrients supplied by the organic manures to the crop have to equalize the quantity of nutrients supplied by inorganic chemical fertilizers, in order to replace chemical fertilizers in organic farming. Since the organic manures release nutrients slowly into the soil over a period of time, the availability of nutrients to the standing crop requires precise estimation. In the present study, the amount of nutrients available in the soil as well as in all the manures was calculated. Moreover, the study included metagenomic analysis of different organic manures used by farmers and gives an insight to the role the microbiome plays in plant growth. Using a formula of STCR‐IPNS (soil test crop response integrated plant nutrition system), the quantities of different combinations of organic manures required to supply nitrogen, phosphorus and potassium (NPK) to sunflower plants were calculated. Organic manure combinations using animal bone meal, neem cake, farmyard manure and vermicompost recorded better growth and yield responses in sunflower plants compared to inorganic chemical fertilizers. Based on the estimation of NPK in the individual manures and in the soil, pot experiments were carried out to understand the effect of organic manures as well as inorganic fertilizers in the vegetative and reproductive growth of sunflower.

The Effects of FR and UVA Irradiation Timing on Multi-Omics of Purple Lettuce in Plant Factories

The synergistic application of far-red (FR) and ultraviolet A (UVA) irradiation presents a promising approach for enhancing growth and the enrichment of secondary metabolites in plants. However, prolonged exposure to these combined light qualities imposes significant stress on plants, hindering their development. Therefore, an initial period of FR irradiation to promote plant growth, followed by a subsequent period of UVA irradiation to enhance the accumulation of plant quality, constitutes a viable strategy. Our study, focusing on purple lettuce, aims to elucidate the response mechanisms of the lettuce leaf under standard white light in commercial production, with the addition of different durations of FR and UVA irradiation, and to explore the complex dynamic changes at the multi-omics level. The results indicate that the duration of FR exposure is crucial in determining biomass-related phenotypes such as fresh weight, while the duration of UVA exposure significantly influences the accumulation of phenotypic markers like anthocyanins. At the transcriptional level, the most extensive transcriptional regulation was observed when FR was applied throughout the entire growth period, and UVA was applied eight days before harvest, significantly impacting pathways such as MAPK signaling cascades, plant hormone signal transduction, photosynthetic processes, and the biosynthesis of secondary metabolites. Metabolomic analysis corroborated the transcriptomic findings, with particular emphasis on antioxidant activity, photoprotection, and defense mechanisms. Our comprehensive analysis suggests that short-term UVA irradiation prior to harvest, based on full growth period FR irradiation, is feasible. The combined application of FR and UVA irradiation fine-tunes plant growth, developmental trajectories, and stress responses by modulating light signals, hormonal signals, and secondary metabolic pathways. These findings not only reveal the adaptive mechanisms of plants to fluctuating light environments but also provide a scientific basis for optimizing light management strategies in controlled plant production systems and precision agriculture.

MsERF17 Promotes Ethylene-Induced Anthocyanin Biosynthesis Under Drought Conditions in Malus spectabilis Leaves.

Drought is an important factor that affects plant anthocyanin biosynthesis. However, the underlying molecular mechanisms remain elusive. Ethylene response factors (ERFs) are pivotal regulators in plant growth and environmental responses, particularly in anthocyanin biosynthesis. This study investigated the leaf colour transition from green to red in Malus spectabilis under drought conditions. This transition was primarily attributed to the accumulation of anthocyanins, specifically cyanidin-3,5-diglucoside and cyanidin-3-O-galactoside. Our findings elucidate the pivotal role of MsERF17 in drought-induced anthocyanin biosynthesis. Biochemical and molecular analyses showed that MsERF17 positively regulates anthocyanin synthesis by binding to promoters of MsbHLH3 and MsF3' H, thereby activating their expression. Moreover, transient overexpression and virus-induced gene silencing of MsERF17 in fruit peel and leaves, respectively, regulated anthocyanin synthesis. The stable transformation of calli further corroborated the positive regulatory function of MsERF17 in anthocyanin biosynthesis. Our results provide novel insights into the mechanism by which MsERF17, induced by ethylene, promotes anthocyanin accumulation through the positive regulation of MsbHLH3 and MsF3'H expression under drought conditions in M. spectabilis leaves.

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.

Modulatory effects of glutamic acid on growth, photosynthetic pigments, and stress responses in olive plants subjected to cadmium stress

Cadmium (Cd) is a toxic heavy metal that severely impacts plant growth and photosynthesis and induces oxidative stress. This study investigates the modulatory effects of glutamic acid (GA) on Olea europaea (olive) seedlings subjected to cadmium stress. The experiment included control, Cd-stressed, GA-treated, and combined Cd and GA-treated groups. Cd exposure significantly reduced plant growth, as evidenced by decreased root length (3.5 cm) and shoot length (9 cm) compared to control plants (5 cm and 12 cm, respectively). Additionally, Cd stress led to a reduction in chlorophyll content (16.2 mg/g fresh weight) and elevated oxidative markers like H2O2 and MDA. The application of GA significantly improved plant growth and physiological parameters, with statistically significant increases in root length (up to 6.5 cm) and shoot length (up to 14 cm) in the combined treatment group (p ≤ 0.05). Furthermore, GA treatment led to a marked elevation in total chlorophyll content (up to 27.5 mg/g fresh weight), compared to 16.2 mg/g in Cd-stressed plants (p ≤ 0.05), reflecting a significant improvement in photosynthetic efficiency. GA also elevated the antioxidant enzyme activity catalase (CAT) and peroxidase (POD), reducing oxidative stress by decreasing hydrogen peroxide and MDA levels. The findings suggest that glutamic acid effectively mitigates Cd-induced phytotoxicity, enhancing stress resistance and promoting plant growth. This research provides valuable insights into using glutamic acid as a possible approach to mitigate heavy metal stress in plants, offering implications for agriculture and environmental management in Cd-contaminated areas. Specific applications may include its use in phytoremediation practices or as a supplement in agricultural management to improve crop resilience in polluted environments. Further research could explore the molecular mechanisms underlying GA’s protective effects and its potential synergy with other biostimulants to enhance heavy metal tolerance in a broader range of crops.