Transporters and phytohormones analysis reveals differential regulation of ryegrass (Lolium perenne L.) in response to cadmium and arsenic stresses.

Cadmium (Cd) and arsenic (As) are two highly toxic heavy metals and metalloids that coexist in many situations posing severe threats to plants. Our investigation was conducted to explore the different regulatory mechanisms of ryegrass (Lolium perenne L.) responding to individual and combined Cd and As stresses in hydroponics. Results showed that the ryegrass well-growth phenotype was not affected by Cd stress of 10 mg·L-1. However, As of 10 mg·L-1 caused rapid water loss, proline surge, and chlorosis in shoots, suggesting that ryegrass was highly sensitive to As. Transcriptomic analysis revealed that the transcription factor LpIRO2 mediated the upregulation of ZIP1 and YSL6 that played an important role in Cd tolerance. We found that the presence of As caused the overexpression of LpSWT12, a process potentially regulated by bHLH14, to mitigate hyperosmolarity. Indoleacetic acid (IAA) and abscisic acid (ABA) contents and expression of their signaling-related genes were significantly affected by As stress rather than Cd. We predict a regulatory network to illustrate the interaction between transporters, transcription factors, and signaling transduction, and explain the antagonism of Cd and As toxicity. This present work provides a research basis for plant protection from Cd and As pollution.

Plant growth promoting bacteria and citric acid promote growth and cadmium phytoremediation in ryegrass.

Based on the growth-promoting effect of plant growth promoting bacteria on plants and the mobilization of Cd by citric acid, an experiment was designed in which the combined treatment of Bacillus megaterium and citric acid promoted ryegrass to repair Cd-contaminated soil. This study aimed to evaluate the effects of different treatments on the antioxidant enzyme activity, photosynthesis intensity, Cd accumulation, and rhizosphere cadmium migration under cadmium contamination conditions. And the soil morphology and structure changes were studied by infrared spectroscopy FourierTransformInfrared(FT-IR) and scanning electron microscope Energy Dispersive Spectrometer(SEM-EDS) before and after different treatments. The results show that the combined treatment of Bacillus megaterium and citric acid significantly improved the oxidative stress defense and plant photosynthesis and increased of rye biomass. rye biomass 1.28 times higher than CK treatment. Joint treatment significantly increased the amount of shoot accumulation of Cd, 2.31 times higher than CK treatment, increased the migration and accumulation of cadmium. FTIR and SEM-EDS also showed that the organic constituents such as O-H, C-O and C-N in soils as a major mechanism for mobilization of the heavy metal Cd. Thus, the combined treatment of Bacillus megaterium and citric acid can promote plant growth, improve the damage to ryegrass caused by single organic acid addition, and improve the plant extraction efficiency, which is a feasible way to repair Cd-contaminated soil through activated extraction system.

The novelty of this study is the combined application of bacteria and chelating agents to ryegrass to improve phytoremediation efficiency. Bacillus giganosus has a good role in promoting the growth of ryegrass. As citrate, a small molecule chelate, can activate heavy metal cadmium and detoxify heavy metals, so it was selected. This study revealed in detail the response of ryegrass to the heavy metal Cd after exogenous addition of Bacillus gigansus and citrate, which is important for the application of cadmium removal by phytoremediation.

Identification of carboxymethyl (CM)-binding proteins derived from Lolium multiflorum pollen extract and antibody reactivity in Brazilian allergic patients.

Lolium multiflorum grass is the major pollen allergen source in the southern region of Brazil, but most of its allergens remain poorly characterized. The aim of this study was to investigate antibody reactivity to L. multiflorum crude and carboxymethyl-ligand extracts in allergic patients and healthy individuals. Ion exchange carboxymethyl (CM) chromatography (CM-Sepharose) was used to isolate proteins (S2) from L. multiflorum crude extract (S1), which were assessed by SDS-PAGE. S1- and S2-specific IgE and IgG4 levels were measured by ELISA using sera from 55 atopic and 16 non-atopic subjects. Reactive polypeptide bands in S1 and S2 were detected by immunoblotting, and the most prominent bands in S2 were analyzed by mass spectrometry (MS-MS). Similar IgE and IgG4 levels were observed to both S1 (IgE median absorbance: 1.22; IgG4 median absorbance: 0.68) and S2 (IgE median absorbance: 1.26; IgG4 median absorbance: 0.85) in atopic subjects. S1 and S2 had positive correlations for IgE and IgG4 (IgE: r=0.9567; IgG4: r=0.9229; P<0.0001) levels. Homology between S1 and S2 was confirmed by IgE (84%) and IgG4 (83%) inhibition. Immunoblotting revealed that the 29-32 kDa band was recognized by 100% of atopic subjects in both S1 and S2. MS-MS analysis identified similarity profile to groups 1 and 5 grass allergens. This study revealed that carboxymethyl-ligand fraction played an important role for pollen allergy diagnosis by containing clinically relevant allergens and constituted a promising candidate for allergen-specific immunotherapy.

Integrated metabolomics, transcriptomics, and proteomics analyses reveal co-exposure effects of polycyclic aromatic hydrocarbons and cadmium on ryegrass (Lolium perenne L.).

Cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs) are prominent soil contaminants found in industrial sites, and their combined effects on plants are not yet fully understood. To investigate the mechanisms underlying the co-exposure of Cd and PAHs and identify key biomarkers for their co-effects, an integrated analysis of metabolomics, transcriptomics, and proteomics was conducted on ryegrass leaves cultivated in soil. In nontarget metabolomics analysis, nine differentially expressed metabolites that were specifically induced by the compound exposure were identified. When combined with the analysis of differentially expressed genes and proteins, it was determined that the major pathways involved in the response to the co-stress of Cd and PAHs were linoleic acid metabolism and phenylpropanoid biosynthesis. The upregulation of 12,13-dihydroxy-9Z-octadecenoic acid and the downregulation of sinapyl alcohol were identified as typical biomarkers, respectively. Compared to scenarios of single exposures, the compound exposure to Cd and PAHs disrupted the oxidation of linoleic acid, leading to alterations in the profiles of linoleate metabolites. Additionally, it intensified hydroxylation, carboxylation, and methylation processes, and interfered with reactions involving coenzyme A, thus inhibiting lignin production. As a result, oxidative stress was elevated, and the cell wall defense system in ryegrass was weakened. The findings of this study highlight the ecological risks associated with unique biological responses in plants co-exposed to Cd and PAHs in polluted soils.

Plant-growth promoting activity of three fungal endophytes isolated from plants living in dehesas and their effect on Lolium multiflorum.

Endophytic fungi have been demonstrated to produce bioactive secondary metabolites, some of which promote plant growth. Three endophytic fungi isolated from healthy plants living in dehesas of Extremadura (Spain) were identified and evaluated for their ability to produce phytohormone-like substances, antioxidant activity, total polyphenol content, phosphate solubilization ability and siderophore and ammonia production. The filtrates and extracts produced by the three endophytes were applied to Lolium multiflorum seeds and seedlings under both in vitro and greenhouse conditions, to analyse their influence on plant growth traits such as germination, vigour index, chlorophyll data, number and length of leaves and roots, and dry weight. All three endophytes, which were identified as Fusarium avenaceum, Sarocladium terricola and Xylariaceae sp., increased the germination of L. multiflorum seeds by more than 70%. Shoot and root length, plant dry weight and the number of roots were positively affected by the application of fungal filtrates and/or extracts, compared with controls. The tentative HPLC-MS identification of phytohormone-like substances, such as gibberellin A2 and zeatin, or the antioxidant acetyl eugenol, may partially explain the mechanisms of L. multiflorum plant growth promotion after the application of fungal filtrates and/or extracts.

Pseudomonas aeruginosa improved the phytoremediation efficiency of ryegrass on nonylphenol-cadmium co-contaminated soil.

The effect of Pseudomonas aeruginosa (P. aeruginosa) on the phytoremediation efficiency of ryegrass on soil contaminated with nonylphenol (NP) and cadmium (Cd) was investigated by pot experiments. Pseudomonas aeruginosa application stimulated the adsorption of Cd by ryegrass and facilitated the biodegradation of NP in the soil. Exogenous P. aeruginosa inoculation increased the activities of urease, dehydrogenase, and polyphenol oxidase in the soil of the T4 treatment by 38.5%, 50.0%, and 56.5% compared to that of the T2 treatment, respectively. There was a significant positive correlation between the activities of dehydrogenase and polyphenol oxidase and the NP removal rate (P < 0.001). The relative abundances of beneficial microorganisms (such as Sphingomonas, Lysobacter, Streptomyces, Chloroflexia, Deltaproteobacteria, and Alphaproteobacteria) were increased as a result of P. aeruginosa inoculation. These microorganisms play important roles in nutrient cycling, Cd adsorption, and NP degradation. Additionally, P. aeruginosa was not the dominate bacterial species at the end of the experiment. According to this study, P. aeruginosa application improved the phytoremediation efficiency of ryegrass on soil contaminated with NP and Cd, with a minimal risk of alien microbial invasion.

Arbuscular Mycorrhizal Fungus "Rhizophagus irregularis" impacts on physiological and biochemical responses of ryegrass and chickpea plants under beryllium stress.

Heavy metals such as beryllium (Be) have been identified as toxic for plants with a negative impact on plant growth. Therefore, there is an urgent need for environmentally friendly techniques to reduce Be toxicity on plant growth and productivity. To this end, arbuscular mycorrhizal fungi (AMF) are widely applied to induce plant growth and stress tolerance. However, how AMF-plant symbiosis can support plants under Be stress has not been studied. Accordingly, we investigated the physiological and biochemical responses of AMF inoculated ryegrass and chickpea plants to Be stress. The associated changes in Be uptake and accumulation, photosynthesis, oxidative stress, carbon and nitrogen metabolism were studied. Soil contamination with Be induced higher Be accumulation, particularly in ryegrass, which consequentially reduced plant growth and photosynthesis. However, photorespiration and oxidative damage (H2O2 accumulation, lipid oxidation, and LOX activity) were increased, mainly in ryegrass. In both plant species, AMF inoculation reduced Be accumulation and mitigated growth inhibition and oxidative damage, but to a more extent in ryegrass. This could be explained by improved photosynthesis as well as the upregulation of osmoprotectants i.e., sucrose and proline biosynthesis pathways. The increase in proline level was consistent with higher nitrogen (N) metabolism as reflected by N level and nitrate reductase. Species-specific responses were recorded and supported by principal component analysis. This study provided insight into the mechanism of AMF's impact on Be-stressed ryegrass and chickpea plants. Hence, the current research suggested that AMF inoculation could be used as a viable strategy to mitigate Be phytotoxicity in ryegrass and chickpea plants.

Cytokinin or ethylene regulation of heat-induced leaf senescence involving transcriptional modulation of WRKY in perennial ryegrass.

Heat stress is a major abiotic stress for temperate plant species with characteristic symptoms of premature leaf senescence. The objectives of this study were to evaluate the physiological effects of cytokinins (CK) and an ethylene inhibitor, aminoethoxyvinylglycine (AVG) on heat-induced leaf senescence in the temperate perennial grass species, perennial ryegrass (Lolium perenne), and to investigate whether WRKY transcription factors (TFs) could be associated with CK- or ethylene-mediated regulation of heat-induced leaf senescence by exogenously applying CK or AVG to perennial ryegrass. Perennial ryegrass plants foliar-sprayed with 6-benzylaminopurine (6-BA), and AVG exhibited prolonged stay-green phenotypes and a lesser degree of leaf senescence under heat stress (35/30°C), as shown by a decline in electrolyte leakage, malondialdehyde content, hydrogen peroxide, and superoxide content, and increased chlorophyll (Chl) content along with reduced activities of Chl-degrading enzymes (pheophytinase and chlorophyllase) and increased activity of Chl-synthesizing enzyme (porphobilinogen deaminase) due to 6-BA or AVG application. The suppression of heat-induced leaf senescence by 6-BA or AVG treatment corresponded with the upregulation of LpWRKY69 and LpWRKY70. The LpWRKY69 and LpWRKY70 promoters were predicted to share conserved cis-elements potentially recognized by TFs in the CK or ethylene pathways. These results indicate that LpWRKY69 and LpWRKY70 may negatively regulate heat-induced leaf senescence through CK or ethylene pathways, conferring heat tolerance in perennial ryegrass.

Redox status upon herbicides application in the control of Lolium multiflorum (2n and 4n) as weed.

Lolium multiflorum Lam. is a winter weed of difficult control found as diploid (2n) and tetraploid plants (4n). Our study aimed to evaluate the responses of antioxidant enzymes and lipid peroxidation, in both diploid and tetraploid ryegrass varieties. Treatments consisted of control plants (without any herbicide application), and four herbicides with different mechanisms of action. Leaf material was collected 36 h after treatment imposition to determine the lipid peroxidation by ferrous oxidation-xylenol (FOX) content, and the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione-S-transferase (GST), and δ-aminolevulinic acid dehydratase (ALAD). Both ryegrass varieties showed oxidative stress mainly due to a downregulated decreased (>31%) in SOD activity and an increase (>32%) in lipid peroxidation (FOX), mainly in ryegrass genotypes exposed to haloxyfop, glyphosate, and iodosulfuron. On the other hand, clethodim-treated plants had an increase in SOD and APX activities, associated with a reduced ALAD activity in both 2n (32%) and 4n (11%) genotypes. In general, the 2n genotype was more affected than the 4n genotype.

Responses of antioxidant enzymes and key resistant substances in perennial ryegrass (Lolium perenne L.) to cadmium and arsenic stresses.

Cadmium (Cd) and arsenic (As) exist simultaneously in soil environment, which poses a serious threat to the safety of agricultural products and forage production. Four Perennial Ryegrass (Lolium perenne L.) cultivars with different accumulation characteristics ('Nicaragua', 'Venus', 'Excellent' and 'Monro') were selected as the material for pot experiment. The coupled responses of key components and related enzyme activities under combined stresses of Cd and As were investigated. key components contents include Non protein sulfhydryl (NPT), glutathione (GSH) and phytochelatins (PCs). The related enzyme includes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), γ-glutamylcysteine synthetase (γ-ECS), glutathione synthetase (GSS), phytochelatin synthetases (PCSase) and arsenate reductase (AR). The results showed that Cd contents of perennial ryegrass were higher than those of As contents with TFCd/As < 1. Cd and As contents in roots were in the higher proportion than those in shoots. Compared to control, POD activities increased by 2.72 folds under 120 mg kg-1 As treatment. The contents of PCs increased by 5.68 folds under 120 mg kg-1 As treatment. Under combined Cd and As stress, the MDA contents and antioxidant enzyme activities of 'Venus' were higher than those of 'Nicaragua'. 'Nicaragua', a high accumulation cultivar. Under the combined stresses of Cd and As, the enzyme activities and the key components were significantly correlated (P < 0.05) with the contents of Cd and As. The tolerance to Cd and As was improved with increase in GSH and PCs contents and γ-ECS, GSS, PCSase and AR activities. In conclusion, the antioxidant enzyme system and key resistant substances of perennial ryegrass have important and antagonistic effects on Cd and As stresses.

Rhizospheric mechanisms of Bacillus subtilis bioaugmentation-assisted phytostabilization of cadmium-contaminated soil.

Plant growth promoting (PGP) traits of inoculation in bioaugmentation assisted phytostabilization of heavy metal-contaminated soil have been well documented. The property of inoculation to immobilize heavy metals is another major contributor to phytostabilization efficiency. This study investigated the effects of inoculation with different concentrations of rhizobacteria Bacillus subtilis on the cadmium (Cd) bioavailability and distribution, enzyme activities, and bacterial community structure in soil planted with ryegrass (Lolium multiflorum L.). Addition of a high dosage of Bacillus subtilis decreased plant malondialdehyde (MDA) amount, increased plant antioxidant enzyme and soil nutrient cycling-involved enzyme activities, and subsequently enhanced biomass by 20.9%. In particular, the inoculation reduced the Cd bioavailability in soil, bioaccumulation coefficient (BCF), translocation factors (TF), and accumulation in ryegrass by 39.1%, 36.5%, 24.2%, and 27.9%, respectively. Furthermore, 16S rRNA gene sequencing analysis of rhizosphere soil revealed microbial community structure alterations (e.g., enrichment of Proteobacteria), eight phenotype regulations, and seventeen Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway transformations accounted for the stress mitigation and Cd immobilization in the presence of inocula. Besides, intracellular accumulation and biofilm sequestration were proposed as primary immobilization mechanisms induced by bioaugmentation.

Arbuscular mycorrhizal fungus facilitates ryegrass (Lolium perenne L.) growth and polychlorinated biphenyls degradation in a soil applied with nanoscale zero-valent iron.

Nanoscale zero-valent iron (nZVI) shows an excellent degradation effect on chlorinated contaminants in soil, but poses a threat to plants in combination with phytoremediation. Arbuscular mycorrhizal (AM) fungus can reduce the phyototoxicity of nZVI, but their combined impacts on polychlorinated biphenyls (PCBs) degradation and plant growth remain unclear. Here, a greenhouse pot experiment was conducted to investigate the influences of nZVI and/or Funneliformis caledonium on soil PCB degradation and ryegrass (Lolium perenne L.) antioxidative responses. The amendment of nZVI significantly reduced not only the total and homolog concentrations of PCBs in the soil, but also the ryegrass biomass as well as soil available P and root P concentrations. Moreover, nZVI significantly decreased leaf superoxide disutase (SOD) activity, while tended to decrease the protein content. In contrast, the additional inoculation of F. caledonium significantly increased leaf SOD activity and protein content, while tended to increase the catalase activity and tended to decrease the malondialdehyde content. The additional inoculation of F. caledonium also significantly increased soil alkaline phosphatase activity, and tended to increase root P concentration, but had no significantly effects on soil available P concentration, the biomass and P acquisition of ryegrass, which could be attributed to the fixation of soil available nutrients by nZVI. Additionally, F. caledonium facilitated PCB degradation in the nZVI-applied soil. Thus, AM fungus can alleviate the nZVI-induced phytotoxicity, showing great application potentials in accompany with nZVI for soil remediation.

Cadmium accumulation in oilseed rape is promoted by intercropping with faba bean and ryegrass.

The mechanisms of intercropping increasing plant biomass, cadmium accumulation, and organic acids secreted in rhizosphere soil are still unclear. Oilseed rape and intercrops were grown in boxes separated either with no barrier between the compartments or by a nylon mesh barrier (37 µm) to license partial root interaction, or a solid barrier to stop any root interactions. Two intercropping systems (oilseed rape-faba bean and oilseed rape-ryegrass) were carried out in soil with Cd content of 5 mg/kg. The intermingling of roots between oilseed rape and faba bean enhanced the biomass of oilseed rape. However, the biomass was negatively affected implying the higher nutrient apportionment to the ryegrass than oilseed rape. Oilseed rape intercropping with both faba bean and ryegrass played a positive role in the shoot Cd concentration of oilseed rape. The intermingling of roots played a positive role in the citric and malic acids when intercropping with faba bean. A remarkable increase in water-soluble Cd and DTPA-Cd content was observed during oilseed rape-faba bean complete root interaction treatment, up to 175.00% and 46.65%, respectively, which compare with the monoculture treatment. In both systems, the translocation factor values were higher for oilseed rape (O-F system) than for the other test plants and were always >1. Thus the Cd removal potential of oilseed rape can be further improved in the future by optimizing agronomic practices and intercropping with faba bean.

Analysis of time varying response on uptake patterns of Cu and Zn ions under application of ethylene diamine disuccinic acid and gibberellic acid in Lolium perenne.

The present study explores the effect of ethylene diamine disuccinic acid (EDDS) and gibberellic acid (GA) application on the phytoextraction of copper and zinc ions by Lolium perenne. When Cu was individually applied, accumulation diminished over time with little translocation from roots to shoots. In contrast, Zn accumulation and damage to roots rapidly increased over 3 days with increase in Zn translocation to shoots. Co-application of Zn to Cu amended treatments enhanced Cu concentration in shoots. For the CuEDDS application, EDDS significantly increased Cu accumulation and the damage to root increased over time, while gibberellic acid applied with Cu and Zn generally lowered metal uptake and decreased cell membrane damage. The application of EDDS and GA-EDDS, by themselves or with Cu and Zn, lowered transpiration and increased translocation, while GA increased transpiration but decreased translocation. EDDS application typically increased metal ion uptake by causing more cell damage, while GA typically lowered the damage and decreased metal uptake even though the transpiration increased over time and plant growth occurred. Furthermore, the behaviour of metal uptake changed over time and, for some treatments, the short-term and long-term response differed greatly. These results show that EDDS can be successfully used in phytoextraction of both Cu and Zn ions by Lolium perenne while GA can resist damage and protect against plant stress.

In vitro gas production and rumen fermentation profile of fresh and ensiled genetically modified high-metabolizable energy ryegrass.

We previously generated a high-metabolizable energy (HME) perennial ryegrass (Lolium perenne) by genetically modifying the plant to increase the leaf lipid content. Although substantial progress has been made toward characterizing physiological changes of HME ryegrass, very limited information exists for feeding value and its suitability for adoption into the pastoral system. In this study, independent HME ryegrass lines with a range of elevated leaf lipid concentrations were analyzed for changes in fatty acids and possible associated changes in the broader nutritional profile, including the gross energy, which was found to increase by 6.8%. Because ryegrass is often ensiled and fermentation in the rumen leads to biohydrogenation of fatty acids as well as enteric methane production, we sought to investigate these effects on HME ryegrass. This was achieved by performing mini-scale silos and using an automated gas measurement system to incubate the material in rumen fluid in vitro for 24 h. Our study included treatments comprising 3 independent HME ryegrass genotypes and wild-type control materials prepared fresh and as silage, employing in total 5 incubation studies, using rumen fluids collected from 4 nonlactating Jersey × Holstein cows. At intervals during the incubation, the production of gases, volatile fatty acids, and the degree of biohydrogenation were measured. Statistical data analysis indicated that differences in the nutritional compositions of the ensiled materials largely reflected those of their fresh counterparts. Incubation of both fresh and ensiled HME ryegrass in rumen fluid resulted in: (1) a greater percentage of valuable unsaturated fatty acids compared with the control; (2) a significant reduction of butyrate; and (3) a 10 to 15% decrease in the methane proportion of the total gas production. We conclude that ensiling could be a convenient option for preserving HME as a locally produced high-value supplementary feed; however, large-scale application needs to be investigated. In this paper we discuss the potential use of HME ryegrass to enhancing forage feeding value and the potential environmental benefits to the pastoral agriculture industry.

Carbohydrate-rich supplements can improve nitrogen use efficiency and mitigate nitrogenous gas emissions from the excreta of dairy cows grazing temperate grass.

Temperate pasture species constitute a source of protein for dairy cattle. On the other hand, from an environmental perspective, their high N content can increase N excretion and nitrogenous gas emissions by livestock. This work explores the effect of energy supplementation on N use efficiency (NUE) and nitrogenous gas emissions from the excreta of dairy cows grazing a pasture of oat and ryegrass. The study was divided into two experiments: an evaluation of NUE in grazing dairy cows, and an evaluation of N-NH3 and N-N2O volatilizations from dairy cow excreta. In the first experiment, 12 lactating Holstein × Jersey F1 cows were allocated to a double 3 × 3 Latin square (three experimental periods of 17 days each) and subjected to three treatments: cows without supplementation (WS), cows supplemented at 4.2 kg DM of corn silage (CS) per day, and cows supplemented at 3.6 kg DM of ground corn (GC) per day. In the second experiment, samples of excreta were collected from the cows distributed among the treatments. Aliquots of dung and urine of each treatment plus one blank (control - no excreta) were allotted to a randomized block design to evaluate N-NH3 and N-N2O volatilization. Measurements were performed until day 25 for N-NH3 and until day 94 for N-N2O. Dietary N content in the supplemented cows was reduced by 20% (P < 0.001) compared with WS cows, regardless of the supplement. Corn silage cows had lower N intake (P < 0.001) than WS and GC cows (366 v. 426 g/day, respectively). Ground corn supplementation allowed cows to partition more N towards milk protein compared with the average milk protein of WS cows or those supplemented with corn silage (117 v. 108 g/day, respectively; P < 0.01). Thus, even though they were in different forms, both supplements were able to increase (P < 0.01) NUE from 27% in WS cows to 32% in supplemented cows. Supplementation was also effective in reducing N excretion (761 v. 694 g/kg of Nintake; P < 0.001), N-NH3 emission (478 v. 374 g/kg of Nmilk; P < 0.01) and N-N2O emission (11 v. 8 g/kg of Nmilk; P < 0.001). Corn silage and ground corn can be strategically used as feed supplements to improve NUE, and they have the potential to mitigate N-NH3 and N-N2O emissions from the excreta of dairy cows grazing high-protein pastures.

Mixture toxicity and uptake of 1-butyl-3-methylimidazolium bromide and cadmium co-contaminants in water by perennial ryegrass (Lolium perenne L.).

Ionic liquids, a kind of emerging and persistent organic contaminants, always coexist with heavy metals in aquatic and terrestrial environments. However, the feasibility of phytoremediation to remove ionic liquids and heavy metals co-contaminants is still unclear. Thus, in this study, the hydroponic experiment was conducted to investigate the combined effect of 1-butyl-3-methylimidazolium bromide ([C4mim]+Br-) and cadmium (Cd2+) on growth and physiological indictors of perennial ryegrass, together with their uptake and translocation by plants. Results show that the exposure of ryegrass to [C4mim]+ and Cd2+ mixture significantly inhibited the biomass growth and affected the photosynthetic pigments contents in leaves. The increases of lipid peroxidation and catalase, peroxidase activity were also observed under the co-exposure experiments. The mixture toxicity of [C4mim]+ and Cd2+ to ryegrass growth showed an additive effect predicted by concentration addition and independent action. [C4mim]+ uptake and acropetal translocation by ryegrass were significantly inhibited with dosing Cd2+. In contrast, [C4mim]+ had no obvious effect on Cd2+ uptake by ryegrass, while enhanced Cd2+ translocation from roots to shoots occurred with increasing [C4mim]+ dosages. These results indicate that the co-contamination of ionic liquids and heavy metals would affect their fates during phytoremediation.

Exploration of Chlorophyll a Fluorescence and Plant Gas Exchange Parameters as Indicators of Drought Tolerance in Perennial Ryegrass.

Perennial ryegrass (Lolium perenne L.) belongs to the common cultivated grass species in Central and Western Europe. Despite being considered to be susceptible to drought, it is frequently used for forming the turf in urban green areas. In such areas, the water deficit in soil is recognized as one of the most important environmental factors, which can limit plant growth. The basic aim of this work was to explore the mechanisms standing behind the changes in the photosynthetic apparatus performance of two perennial ryegrass turf varieties grown under drought stress using comprehensive in vivo chlorophyll fluorescence signal analyses and plant gas exchange measurements. Drought was applied after eight weeks of sowing by controlling the humidity of the roots ground medium at the levels of 30, 50, and 70% of the field water capacity. Measurements were carried out at four times: 0, 120, and 240 h after drought application and after recovery (refilling water to 70%). We found that the difference between the two tested varieties' response resulted from a particular re-reduction of P700+ (reaction certer of PSI) that was caused by slower electron donation from P680. The difference in the rate of electron flow from Photosystem II (PSII) to PSI was also detected. The application of the combined tools (plants' photosynthetic efficiency analysis and plant gas exchange measurements) allowed exploring and explaining the specific variety response to drought stress.

Interactions between electrokinetics and rhizoremediation on the remediation of crude oil-contaminated soil.

An electrokinetics (EK)-enhanced phytoremediation system with ryegrass was constructed to remediate crude oil-polluted soil. The four treatments employed in this study included (1) without EK or ryegrass (CK-NR), (2) EK only (EK-NR), (3) ryegrass only (CK-R), and (4) EK and ryegrass (EK-R). After 30d of ryegrass growth, EK at 1.0 V·cm-1 with polarity reversal (PR-EK) was supplied for another 30 d. The electric current was recorded during remediation. The pH, electrical conductivity, total petroleum hydrocarbon content (TPH), 16S rDNA, functional genes of AlkB, Nah, and Phe, DGGE, and dehydrogenase activity in soil were measured. The physical-chemical indexes of the plant included the length, dry mass, and chlorophyll contents of the ryegrass. Results showed that EK-R removed 18.53 ±â€¯0.53% of TPH, which was higher than that of other treatments (13.34-14.31%). Meanwhile, the values of 16S rDNA, AlkB, Nah, Phe, and dehydrogenase activity in the bulk soil of EK-R all increased. Further clustering analysis with numbers of genes and DGGE demonstrated that EK-R was similar to the ryegrass rhizosphere soils in both EK-R and CK-R, while the EK treatment of EK-NR was similar to that of CK-NR without EK and ryegrass. These results indicate that the PR-EK treatment used in this experiment successfully enlarged the existing scale of the rhizosphere microorganisms, improved microbial activity and enhanced degradation of TPH.

Differentiation between physical and chemical effects of oil presence in freshly spiked soil during rhizoremediation trial.

Petroleum contamination and its remediation via plant-based solutions have got increasing attention by environmental scientists and engineers. In the current study, the physiological and growth responses of two diesel-tolerant plant species (tolerance limit: 1500-2000 mg/kg), Italian ryegrass (Lolium multiflorum) and Birdsfoot trefoil (Lotus corniculatus), have been investigated in vegetable oil- and diesel oil-amended soils. A long-term (147-day) greenhouse pot experiment was conducted to differentiate the main focus of the study: physical and chemical effects of oil (vegetable and diesel) in freshly spiked soils via evaluating the plant performance and hydrocarbon degradation. Moreover, plant performance was evaluated in terms of seed germination, plant shoot biomass, physiological parameters, and root biomass. Addition of both diesel oil and vegetable oil in freshly spiked soils showed deleterious effects on seedling emergence, root/shoot biomass, and chlorophyll content of grass and legume plants. Italian ryegrass showed more sensitivity in terms of germination rate to both vegetable and diesel oil as compared to non-contaminated soils while Birdsfoot trefoil reduced the germination rate only in diesel oil-impacted soils. The results of the current study suggest that both physical and chemical effects of oil pose negative effects of plant growth and root development. This observation may explain the phenomenon of reduced plant growth in aged/weathered contaminated soils during rhizoremediation experiments.