Growth Of Rice Seedlings Research Articles

The Effects of Polystyrene Microplastics and Copper Ion Co-Contamination on the Growth of Rice Seedlings.

Microplastics (MPs) are emerging pollutants of global concern, while heavy metals such as copper ions (Cu2+) are longstanding environmental contaminants with well-documented toxicity. This study investigates the independent and combined effects of polystyrene microplastics (PS-MPs) and Cu on the physiological and biochemical responses of rice seedlings (Oryza sativa L.), a key staple crop. Hydroponic experiments were conducted under four treatment conditions: control (CK), PS-MPs (50 mg·L-1), Cu (20 mg·L-1 Cu2+), and a combined PS-MPs + Cu treatment. The results showed that PS-MPs had a slight stimulatory effect on root elongation, while Cu exposure mildly inhibited root growth. However, the combined treatment (PS-MPs + Cu) demonstrated no significant synergistic or additive toxicity on growth parameters such as root, stem, and leaf lengths or biomass (fresh and dry weights). Both PS-MPs and Cu significantly reduced peroxidase (POD) activity in root, stem, and leaf, indicating oxidative stress and disrupted antioxidant defenses. Notably, in the combined treatment, PS-MPs mitigated Cu toxicity by adsorbing Cu2+ ions, reducing their bioavailability, and limiting Cu accumulation in rice tissues. These findings reveal a complex interaction between MPs and heavy metals in agricultural systems. While PS-MPs can alleviate Cu toxicity by reducing its bioavailability, they also compromise antioxidant activity, potentially affecting plant resilience to stress. This study provides a foundation for understanding the combined effects of MPs and heavy metals, emphasizing the need for further research into their long-term environmental and agronomic impacts.

Mitigation Effect of Exogenous Nano-Silicon on Salt Stress Damage of Rice Seedlings

Salt stress represents a significant abiotic stress factor that impedes the growth of rice. Nano-silicon has the potential to enhance rice growth and salt tolerance. In this experiment, the rice variety 9311 was employed as the test material to simulate salt stress via hydroponics, with the objective of investigating the mitigation effect of foliar application of nano-silicon on rice seedlings. The results demonstrated that NaCl stress markedly impeded the growth of rice seedlings after seven days of NaCl treatment. The foliar application of nano-silicon followed by NaCl stress alleviated the growth of rice seedlings, markedly improved the spatial conformation of the root system, and enhanced photosynthesis compared with that of NaCl stress alone. The activities of antioxidant enzymes were improved. The contents of antioxidants were increased, and the over-accumulation of ROS was reduced. Furthermore, the foliar application of nano-silicon was found to enhance the uptake of Si4+, K+, and Ca2+ in plants, while simultaneously reducing Na+ and Cl− accumulation. Additionally, the content of IAA, CTK, GA, JA, and SA was increased, and ABA was decreased. In conclusion, the foliar application of nano-silicon has been demonstrated to alleviate salt stress injury and improve the growth of rice seedlings.

Biopriming of seeds with microbial biostimulant (Bacillus megaterium ) on improvement of seedling growth, biochemical and root traits of rice (Oryza sativa L.)

This study aimed to evaluate the potential of Bacillus megaterium in improvingseed germination and rice seedling's morpho-physiological andbiochemical traits. The experiment was conducted using a completely randomizeddesign to evaluate the effect of different concentrations of the biostimulantB. megaterium on rice seedlings growth and development undernursery conditions. Biopriming seeds with B. megaterium significantly enhancedseed germination and seedling traits, such as seedling shoot androot length, seedling height, number of leaves, seedling vigor, and shootand root dry biomass, compared to the untreated control. Among the treatments,biopriming seeds with B. megaterium at a concentration of 10g kg-1resulted in the greatest improvements across all the recorded parameters.Root traits such as total root length, surface area, average root diameter,root volume, and root tips and forks were also significantly enhanced. Additionally,biochemical changes like total chlorophyll and soluble protein contentshowed notable improvements with the concentration of B. megaterium. Hence, these results suggest that biopriming seeds with B. megateriumare an efficient strategy to improve seed germination and shoot and rootvigor in rice seedlings.

Screening the Effect of Burkholderia glumae on Seed Germination and Seedling Growth of Rice (Oryza sativa L.)

The increasing prevalence of diseases like Burkholderia glumae-produced bacterial panicle blight has an influence on rice production worldwide. In rice plants, the symptoms caused by the pathogen include browning of the leaf sheath, grain rot, and seedling rot. It is observed that the pathogen enters the plant through contaminated seeds and environmental sources of the microbe. The present study analysed the effect of B.glumae on seed germination and root- shoot growth under control condition, and also the screening of different varieties against BPB under glasshouse condition.In all the studied varieties growth responses were varied whereas healthy seeds showed maximum responses followed by artificially infected and naturally infected seeds respectively for root and shoot growth.

Investigating the mechanism of auxin-mediated fulvic acid-regulated root growth in Oryza sativa through physiological and transcriptomic analyses.

As rice is one of the most crucial staple food sources worldwide, enhancing rice yield is paramount for ensuring global food security. Fulvic acid (FA), serving as a plant growth promoter and organic fertilizer, holds significant practical importance in studying its impact on rice root growth for improving rice yield and quality. This study investigated the effects of different concentrations of FA on the growth of rice seedlings. The results indicated that 0.05 g/L FA could promote the growth of rice seedlings, while 0.5 g/L FA inhibited root growth, reduced cell activity and enzyme activity in the root tips, and accumulated reactive oxygen species in root cells. To further elucidate the molecular mechanisms underlying these effects, we performed transcriptomic analysis and found that auxin (Aux) may be involved in the growth process mediated by FA. Furthermore, transcriptome heatmap analysis revealed a significant upregulation of the Aux/indoleacetic acid (Aux/IAA) gene family after FA treatment, suggesting that this gene family plays a crucial role in the impact of FA on root growth. Additionally, by detecting endogenous Aux content and adding exogenous Aux inhibitors, we confirmed the involvement of FA in rice seedling root growth as well as in the synthesis and transduction pathway of Aux.

Plant growth-promoting Bacillus amyloliquefaciens orchestrate homeostasis under nutrient deficiency exacerbated drought and salinity stress in Oryza sativa L. seedlings.

Nutrient deficiency intensifies drought and salinity stress on rice growth. Bacillus amyloliquefaciens inoculation provides resilience through modulation in metabolic and gene regulation to enhance growth, nutrient uptake, and stress tolerance. Soil nutrient deficiencies amplify the detrimental effects of abiotic stresses, such as drought and salinity, creating substantial challenges for overall plant health and crop productivity. Traditional methods for developing stress-resistant varieties are often slow and labor-intensive. Previously, we demonstrated that plant growth-promoting rhizobacteria Bacillus amyloliquefaciens strain SN13 effectively alleviates stress induced by sub-optimum nutrient conditions in rice. In this study, we evaluated the effectiveness of SN13 in reducing the compounded impacts of drought and salinity under varying nutrient regimes in rice seedlings. The results demonstrated that PGPR inoculation not only improved the growth parameters, nutrient content, and physio-biochemical characteristics under nutrient-limited conditions, but also reduced the oxidative stress markers. The altered expression of stress-related and transcription factor genes (USP, DEF, CYP450, GST, MYB, and bZIP) revealed the regulatory effect of PGPR in enhancing stress tolerance through these genes. GC-MS-based untargeted metabolomic analysis revealed that PGPR significantly influenced various metabolic pathways, including galactose metabolism, fructose and mannose metabolism, and fatty acid biosynthesis pathways, suggesting that PGPR affects both energy production and stress-protective mechanisms, facilitating better growth and survival of rice seedlings.

U + LSTM-F: A data-driven growth process model of rice seedlings

Accurately predicting the growth status of rice seedlings and understanding their growth rate and health status in a timely manner helps adjust the growth cycle and management measures. By predicting the growth status of the seedlings, the best time for transplanting can be selected, improving the survival rate and overall health of the seedlings, thereby enhancing yield and quality. Therefore, this study proposes a data-driven time-series model, the U + LSTM-F model, for predicting the growth status of Wuyou Rice 4 seedlings. First, the U-Net model is employed to segment sequentially collected images, extracting features such as leaf age and stem length of the rice seedlings. Subsequently, the collected ambient temperature and humidity data are aligned with the leaf age and stem length data. Finally, the LSTM model is used for time-series analysis, enabling the model to learn the temporal relationship between environmental and growth data and predict the growth trend of the rice seedlings. Additionally, an attention mechanism is introduced to enhance model performance, and the model's effectiveness is evaluated using multiple quantitative metrics. The proposed model achieves an RMSE of 0.032 and MAPE of 0.895 % for leaf age prediction, and an RMSE of 0.067 and MAPE of 0.814 % for stem length prediction. The experimental results show that this data-driven approach, which combines growth data with environmental data, exhibits high accuracy in predicting the leaf age and stem length of rice seedlings. This provides a more accurate tool for predicting the growth of rice seedlings, offering valuable insights for rice seedling cultivation research.

Genome Wide Association Analysis for Uniform Coleoptiles Emergence and Early Seedling Growth in Rice

Early seedling vigour (ESV) is a complex trait in rice. Detection of QTLs/genes controlling these traits can help us in enhancing the yield potential in rice varieties. Association mapping is a technique based on the principle of linkage disequilibrium that is used to find genes or quantitative trait loci (QTL) underlying the complex traits. In this study of haplotype breeding 281 rice genotypes were taken. ANOVA analysis showed P- value for traits and genotypes was found significant. Similarly, P-value for interaction between the traits and genotypes was also found to be highly significant (1.8663*10-208). Further, mean germination data positively correlated with mean shoot length, mean leaf number, mean culm diameter, mean shoot dry weight, and mean shoot area of 21st day among the 281 genotypes. Among the 281 number of genotypes, 111 genotypes are found to be in PCA1 and 170 genotypes are found to be in PCA2 based on the phenotypic analysis. PCA1 component constituted 29.93% and PCA2 constituted the 13.68% of total variation in the analysis. Besides, whole genome phylogenetic analysis showed three major groups of which Group 1 consists of 215 genotypes, group 2 consists of 38 genotypes and group 3 consists of 28 genotypes respectively. Especially, both the subgroups II and III comprised of the unique genotypes from the indica and aus subpopulations of rice. In this analysis, 16 significant associations (LOD Score >7) for different traits were identified using the three different models (MLM, farmCPU, and blink) for GWAS studies Especially, one major QTL was identified for the mean coleoptiles’ emergence for 10 DAS on 11th chromosome (18983591) which explained 49% of the phenotypic variance. Additionally, another major QTL contributing to the shoot length variation of 29.75% was identified in the Chr02 (32954393) for shoot length trait on 28 DAS. A candidate gene namely Os02g0778400 UMP/CMP kinase A/adenylate kinase (LOC_Os02g53790) was located in the significant SNP region of the GWAS analysis. Further characterization of this gene would assist in elucidation of the mechanism regulating the early seedling length in rice under direct seeded rice.

Melatonin Mediates Trade–Off in Antioxidant Responses and Nitrogen Metabolism and Benefits the Growth of Fragrant Rice Seedlings Under Light–Nitrogen Levels

Melatonin Mediates Trade–Off in Antioxidant Responses and Nitrogen Metabolism and Benefits the Growth of Fragrant Rice Seedlings Under Light–Nitrogen Levels

Influence of Foliar Application of Nanoparticles on Low Temperature Resistance of Rice Seedlings.

Chilling stress, a common abiotic factor, adversely affects the growth and biomass of rice seedlings during the early stages, ultimately reducing the yield. Effective strategies to mitigate these negative impacts are essential for improving rice productivity. The application of nanotechnology in agriculture, particularly nanoparticles (NPs), has shown a promising effect in alleviating chilling stress in plants. This study evaluates the effects of various nanoparticles, ZnO (0, 50, 100, and 200 mg/L), Fe2O3 (0, 50, 75, and 100 mg/L), TiO2 (0, 50, 75, and 100 mg/L), and CeO2 (0, 50, 75, and 100 mg/L) on the chilling resistance with one control (a water spray) under a normal temperature. Four rice cultivars: LLY-7108 and XZX-6 (Low-temperature-tolerant), and LLY-32 and ZJZ-17 (Low-temperature-susceptible) were tested in this experiment. Rice seedlings were subjected to low temperature conditions (12 h light 14 °C/12 h dark, at 10 °C) for five days, followed by seven days of recovery. The results of this study demonstrate that NPs significantly enhanced seedling height fresh/dry weight and root length compared to untreated controls under chilling stress. NP treatment also reduced the reactive oxygen species (ROS), malondialdehyde (MDA), and proline content, while enhancing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, thereby mitigating oxidative damage. The four rice varieties exhibited clear signs of rapid growth recovery and positive physiological changes due to NPs' application. Among the tested cultivars, LLY-7108 showed the most substantial recovery and physiological responses, while ZJZ-17 exhibited the least. The findings of this study indicate that the foliar application of ZnO (100 mg/L), Fe2O3 (50 mg/L), TiO2 (50 mg/L), and CeO2 (75 mg/L) NPs effectively mitigates chilling stress in rice seedlings, likely by enhancing the antioxidant enzymatic activity while reducing the oxidative damage. This study highlights the potential of NPs as effective agents in reducing the adverse effects of chilling stress on rice.

Bacillus altitudinis Mediated Lead Bioremediation for Enhanced Growth of Rice Seedlings.

Lead (Pb) is a hazardous environmental pollutant that threatens soil health, water quality, and agricultural productivity. Plant growth-promoting rhizobacteria (PGPRs) mediated bioremediation is considered as an eco-friendly approach for agro-environmental sustainability. This study investigated the Pb bioremediation potential of Bacillus altitudinis (IHBT-705). The results revealed that IHBT-705 strain tolerated upto 15mM of Pb, possessed 96% Pb bioaccumulation efficiency, and also maintained its plant growth-promoting (PGP) traits under Pb stress. Furthermore, IHBT-705 strain treated with 15mM Pb solution (IHBT-W) and soil containing 15mM Pb treated with IHBT-705 inoculum (IHBT-S) ameliorated the detrimental effects of Pb stress. Both IHBT-W and IHBT-S treatment significantly improved the shoot length, root length, total roots, chlorophyll content, and antioxidants enzyme activity of the rice seedlings as compared to the seedlings treated with 15mM Pb solution (Pb-W) and soil containing 15mM Pb (Pb-S). Also, IHBT-W and IHBT-S treatment decreased the Pb content in the rice plant by 97 and 96% over their respective Pb-W and Pb-S plants. Overall, our research underscores the remarkable Pb bioremediation potential of IHBT-705, offering a promising avenue for dual function, i.e. improving soil health and promoting plant growth under Pb contamination.

Allelochemicals Released from Rice Straw Inhibit Wheat Seed Germination and Seedling Growth

Recently, returning rice straw to soil has become a common problem in wheat production because it causes decreased wheat seedling emergence. Allelopathy is an important factor affecting seed germination. However, the effects of rice straw extracts on wheat seed germination and seedling growth remain unclear. Wheat seeds and seedlings were treated with 30 g L−1 of rice leaf extracts (L1), 60 g L−1 of rice leaf extracts (L2), 30 g L−1 of rice stem extracts (S1), 60 g L−1 of rice stem extracts (S2) and sterile water (CK) to study the allelopathic effects of rice straw extracts on wheat seed germination and seedling growth. The α-amylase and antioxidant enzyme activities in wheat seeds; the agronomic traits, photosynthetic indicators, and nutrient contents of wheat seedlings; and the phenolic acids in rice stem extracts were determined. Common allelochemicals, including 4-hydroxybenzoic acid, hydrocinnamic acid, trans-cinnamic acid, vanillic acid, benzoic acid, protocatechualdehyde, caffeic acid, syringic acid, sinapic acid, and salicylic acid, were detected in rice stem extracts. Low-concentration rice leaf and stem extracts (30 g L−1) had no effect on the germination rate of wheat seeds. High-concentration (60 g L−1) rice stem and leaf extracts decreased the seed germination rate by 11.00% and 12.02%. Rice stem extract (60 g L−1) decreased the α-amylase activity, and gibberellin content of wheat seeds but increased superoxide dismutase, peroxidase, and catalase activities and malondialdehyde content in wheat seeds. Allelochemicals entered the internal tissues of wheat seeds, where they decreased the gibberellin content and α-amylase activity and increased the antioxidant enzyme activity, ultimately leading to an inhibitory effect on seed germination. Rice stem and leaf extracts decreased the SPAD value and photosynthetic indicators of wheat seedlings. Rice stem extract (60 g L−1) decreased the fresh weight and root length of wheat seedlings by 31.37% and 45.46%. Low-concentration rice leaf and stem extract (30 g L−1) had no effect on the nutrient contents of wheat seedlings. Rice leaf and stem extracts (60 g L−1) decreased the nitrogen and potassium contents of wheat seedlings. These results indicated that low-concentration rice leaf and stem extract (30 g L−1) had no effect on wheat seed germination and the high-concentration rice stem extract (60 g L−1) released allelochemicals and inhibited wheat seed germination and seedling growth. These findings provide a basis for the improvement of straw return techniques.

Exogenous MgH2-derived hydrogen alleviates cadmium toxicity through m6A RNA methylation in rice

Cadmium (Cd) contamination poses a substantial threat to crop yields and human health. While magnesium hydride (MgH2) has been reported as a hydrogen (H2) donor that promotes plant growth under heavy metal contamination, its role in rice remains elusive. Herein, seedlings of Oryza sativa L. Japonica variety Zhonghua 11 (ZH11) were selected and exposed to 20 µL of 1-mol/L cadmium chloride (CdCl2) solution via hydroponics to simulate Cd stress. Meanwhile, 0.1 mg of MgH2 was used to slow-release H2 to the experimental group to explore its potential effects on rice over a 2-week period. The results indicated that Cd exposure severely inhibited the growth and development of ZH11 rice seedlings. However, the exogenous slow-release of H2 from MgH2 effectively mitigated this inhibitory effect by restoring the balance of reactive oxygen species (ROS), maintaining endogenous H2 homeostasis, and supporting the photosynthetic system. High-performance liquid chromatography analysis revealed that exogenous H2 reduces m6A RNA methylation levels in mRNA under Cd stress. Consequently, MeRIP-seq was conducted to investigate the effect of Cd exposure in rice in the presence and absence of H2. The m6A modifications were enriched at the start codon, stop codon, and 3′ UTR. By integrating RNA-seq data, 118 transcripts were identified as differentially methylated and expressed genes under Cd stress. These gene annotations were associated with ROS, biological stress, and hormonal responses. Notably, 297 differentially methylated and expressed genes were identified under Cd stress in the presence of H2, linked to heavy metals, protein kinases, and calcium signaling regulation. Cd strongly activates the MAPK pathway in response to stress. Exogenous H2 reduces Cd accumulation as well as enhances plant tolerance and homeostasis by lowering m6A levels, thereby decreasing the mRNA stability of these genes. Our findings indicate that MgH2, by supplying H2, regulates gene expression through m6A RNA methylation and confers Cd tolerance in rice. This study provides potential candidate genes for studying the remediation of heavy metal pollution in plants.

Plant growth-promoting Bacillus cereus MCC3402 facilitates rice seedling growth under arsenic-spiked soil

Microorganisms can solve the global problem of arsenic (As) contamination in soil and water, by eliminating the hazardous metalloid from contaminated habitats. A native As-resistant PMM6 strain was isolated from the tainted agricultural field in Durgapur, India. Following phenotypic investigations, fatty acid methyl ester analysis, and 16S rDNA sequence-based homology, it was identified as Bacillus cereus. Various analytical techniques such as atomic absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy studies revealed a positive correlation between the strain's resistance properties against arsenate (75 mM) and arsenite (25 mM) and the biosorption and bioaccumulation of arsenic. The strain exhibited several important plant growth-promoting traits, including indole-3-acetic acid production (110.0±0.33μg/mL), 1-aminocyclopropane-1-carboxylate deaminase activity (2334.2±1.90 nm α-ketobutyrate/mg protein/h), phosphate solubilization, and siderophore production (68.0±2%). These traits facilitated the growth augmentation of rice seedlings under As stress, both in terms of physiological and biochemical parameters. Compared to uninoculated soil, the use of strain PMM6 helped to reduce As mobilization and oxidative stress in rice seedlings growing in As-spiked soil. Therefore, strain PMM6 holds the potential as bioremediator to restore As-contaminated agricultural lands while also promoting the growth of rice seedlings. It could thus be utilized in the bioremediation of As-contaminated agricultural lands in the near future.

The role of Ni- and Cd-resistant rhizobacteria in promoting the growth of rice seedlings and alleviating the combined phytotoxicity of Ni and Cd

The problem of potentially toxic metal pollution is increasingly acute with the development of human society. In this study, we investigated the remediation of nickel (Ni) and cadmium (Cd) co-contamination through inoculating rice with three new-isolated Ni- and Cd-resistant plant growth-promoting rhizobacteria (PGPR) Y3, Y4, and Y5. These three strains possessed growth-promoting properties, including 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, the ability of indoleacetic acid (IAA) production, phosphate solubilization, siderophores production, and exopolysaccharide (EPS) development. According to 16S rDNA sequence homology, strains Y3, Y4, and Y5 were identified as Pseudomonas sp., Chryseobacterium sp., and Enterobacter sp., respectively. Based on the results of rice germination experiments conducted under combined toxicity, we set the contamination concentrations for Ni2+ at 20 μg mL−1 and Cd2+ at 40 μg mL−1. Then we conducted potting experiments at these concentration levels to study the effects of strains Y3, Y4, and Y5 on rice growth under synergistic Ni and Cd stress. The results indicated that the inoculated strains Y3, Y4, and Y5 were effective in promoting the growth of rice seedlings under the combined stress of Ni and Cd, and conferring tolerance to Ni and Cd by increasing the antioxidant enzyme activities of the seedlings. Among them, strain Y3 exhibited stronger ACC deaminase activity, IAA production capacity, and EPS production capacity, showing the most pronounced growth-promoting effect on rice. It was demonstrated that after inoculation with strain Y3, the germination rate of rice seeds increased by 43 %, the fresh weight of stems improved by 35 %, and the chlorophyll content enhanced by 70 % and other growth-promoting phenomena. Additionally, under Ni and Cd stress, strain Y5 performed better than strain Y4 in terms of IAA production capacity and its influence on rice root growth, suggesting that IAA production might play a specifically essential role in root growth under Ni and Cd stress.

Impact of root-stem coupling damage from mechanical transplanting on the growth of large rice seedlings

Impact of root-stem coupling damage from mechanical transplanting on the growth of large rice seedlings

Regional propolis extracts suppress Fusarium fujikuroi and boost rice seedling growth and response against Bakanae disease

Bakanae, caused by Fusarium fujikuroi, is a serious seed-borne disease affecting rice production worldwide. Herein, we investigated the potential of propolis, a natural honeybee product, collected from three geographic locations in Egypt: North (Menofia), Middle (Cairo), and South (Sohag), and extracted with four different solvents (ethanol, olive oil, hexane, and water) as a sustainable eco-friendly alternative to control the Bakanae disease in rice. In vitro experiments showed that propolis extracts exhibited antifungal activity against F. fujikuroi and significantly suppressed its mycelial growth and sporulation. The antifungal activity of propolis extracts was associated with its chemical composition which varied depending on geographical origin, and the extraction solvents. Moreover, SEM-based analysis revealed that ethanolic extract of northern propolis prominently altered the microconidia morphology of F fujikuroi, which shrunken and seemed to lose their viability. These findings were further confirmed in vivo under greenhouse conditions. Soaking F fujikuroi-inoculated rice seeds in 1000 ppm of propolis extract significantly reduced the bakanae disease incidence, and disease severity index compared to mock-treated controls. Although infection with F fujikuroi induced the accumulation of H2O2, the application of propolis extracts alleviated oxidative stress and significantly reduced the H2O2 levels within infected rice seedlings. Moreover, propolis extracts enhanced the profile of enzymatic antioxidants (guaiacol-dependent peroxidase [POX] and polyphenol oxidase [PPO]) in F. fujikuroi-infected rice seedlings. Finally, Propolis extracts-treated rice seedlings exhibited higher transcript levels of three PTI-marker genes including nonexpressor of pathogenesis-related genes 1 (OsNPR1), WRKY transcription factor 21(OsWRKY21), and phenylalanine ammonia-lyase (OsPAL1), which are associated with systemic acquired resistance (SAR) and crucial for the plant's defense response against pathogens. Collectively, these findings suggest that propolis might be a promising sustainable, eco-friendly alternative to control bakanae disease and other fungal seed-borne phytopathogens due to its antifungal properties and ability to induce a complex multilayered defense system within infected plants.

Endophytic consortium exhibits varying effects in mitigating cadmium toxicity in rice cultivars with distinct cadmium accumulation capacities

Cadmium (Cd)-contaminated rice is the main source of Cd exposure that threatens food safety and human health. While plant growth-promoting bacteria (PGPB) have been reported to reduce Cd toxicity in rice, the effect of endophytic consortium is less understood compared to the single strain. Here, we reported that the PGPB consortium consisting of Cd-tolerant endophytic bacteria Pseudomonas sp. 4N2 and Bacillus sp. TB1 increased extracellular polymeric substance secretion and demonstrated a higher Cd removal rate compared to individual 4N2 and TB1. Further, two rice cultivar, namely the low-Cd-accumulating (LA) cultivar 728B and the high-Cd-accumulating (HA) cultivar BB, were inoculated with the 4N2-TB1 consortium. As expected, the consortium had a more pronounced effect on 728B, from which the endophytic bacteria were screened. The 4N2-TB1 consortium was found to facilitate the growth of rice seedlings and enhance their antioxidation activity. Moreover, the consortium significantly reduced Cd transfer coefficient from root to shoot through Cd immobilization in rice roots, resulting in a reduction from 30 % to 6 % in 728B and from 31 % to 13 % in BB. Furthermore, alpha-diversity analysis indicated an increased diversity and richness of the root bacterial community after 4N2-TB1 inoculation. Also, redundancy analysis confirmed a positive correlation between rice biomass and Cd content with a specific assemblage of bacteria including Bacillus and Leifsonia. These results demonstrated that the 4N2-TB1 consortium may alleviate Cd stress in rice cultivars through recruiting PGPB and Cd-binding bacteria on the root surface, thus strengthening the immobilization of Cd in rice roots.

Multiomics Analysis of the Mechanism by Which Gibberellin Alleviates S-Metolachlor Toxicity in Rice Seedlings.

S-metolachlor is a selective pre-emergence herbicide used in dryland. However, it is challenging to employ in paddy fields due to its phytotoxic effects on rice. As a common phytohormone, Gibberellin-3 (GA3) is inferred to have the ability to alleviate herbicide phytotoxicity. This study first quantitatively verified the phytotoxicity of s-metolachlor to rice and then demonstrated the mitigative effect of GA3 on these adverse reactions. Furthermore, a transcriptome of rice seedlings subjected to different treatments was constructed to assemble the reference genes, followed by comparative metabolomics and proteomics analyses. Metabolomics revealed an enrichment of flavonoid metabolites in the group of adding GA3, and these flavonoids can eliminate ROS in plants. Proteomics analysis indicated that differential proteins were enriched in the phenylpropanoid biosynthesis pathway responsible for the synthesis of flavonoids and that the functions of most differential proteins are associated with peroxidase. The proteome, combined with the transcriptome, revealed that the expressions of proteins and genes was related to the POD activity in the group of adding GA3. It was speculated that the elimination of ROS is key to alleviating the stress of s-metolachlor on rice growth. It was inferred that the mechanism of GA3 in alleviating the phytotoxicity of the substance s-metolachlor is by increasing the activity of the POD and influencing the growth of rice seedlings through the restoration of flavonoid synthesis. In this study, we screened GA3 as a safener to alleviate the phytotoxicity of s-metolachlor on rice. On this basis, the mechanism of alleviating phytotoxicity was studied. The application range of s-metolachlor might be expanded, providing a new supplementary method for weed control and herbicide resistance management.

The Diterpene Isopimaric Acid Modulates the Phytohormone Pathway to Promote Oryza sativa L. Rice Seedling Growth.

Many plant secondary metabolites are active and important in the regulation of plant growth. Certain plant-derived diterpenes are known to promote plant growth, but the pathways by which this promotion occurs are still unknown. Activity screening revealed that the plant-derived diterpene isopimaric acid exhibits growth-promoting activity in rice (Oryza sativa L.) seedlings. Furthermore, 25 μg/mL of isopimaric acid promoted the growth of 15 self-incompatible associated populations from different rice lineages to different extents. Quantitative analyses revealed a significant decrease in the concentration of the defense-related phytohormone abscisic acid (ABA) following treatment with isopimaric acid. Correlation analysis of the phytohormone concentrations with growth characteristics revealed that the length of seedling shoots was significantly negatively correlated with concentrations of 3-indole-butyric acid (IBA). Moreover, the total root weight was not only negatively correlated with ABA concentrations but also negatively correlated with concentrations of isopentenyl adenine (iP). These data suggest that isopimaric acid is able to influence the phytohormone pathway to balance energy allocation between growth and defense in rice seedlings and also alter the correlation between the concentrations of phytohormones and traits such as shoot and root length and weight. We provide a theoretical basis for the development and utilization of isopimaric acid as a plant growth regulator for rice.