Genome-Wide Identification, Characterization, and Expression of TCP Genes Family in Orchardgrass.

Plant-specific TCP transcription factors regulate several plant growth and development processes. Nevertheless, little information is available about the TCP family in orchardgrass (Dactylis glomerata L.). This study identified 22 DgTCP transcription factors in orchardgrass and determined their structure, phylogeny, and expression in different tissues and developmental stages. The phylogenetic tree classified the DgTCP gene family into two main subfamilies, including class I and II supported by the exon-intron structure and conserved motifs. The DgTCP promoter regions contained various cis-elements associated with hormones, growth and development, and stress responses, including MBS (drought inducibility), circadian (circadian rhythms), and TCA-element (salicylic acid responsiveness). Moreover, DgTCP9 possibly regulates tillering and flowering time. Additionally, several stress treatments upregulated DgTCP1, DgTCP2, DgTCP6, DgTCP12, and DgTCP17, indicting their potential effects regarding regulating responses to the respective stress. This research offers a valuable basis for further studies of the TCP gene family in other Gramineae and reveals new ideas for increasing gene utilization.

Genome-wide identification of MADS-box gene family in orchardgrass and the positive role of DgMADS114 and DgMADS115 under different abiotic stress.

Abiotic stress, a major factor limit growth and productivity of major crops. Orchardgrass is one of the most important cool-season forage grasses in the world, and it is highly tolerant to abiotic stress. The MADS-box transcription factor family is one of the largest families in plants, and it plays vital roles in multiple biological processes. However, MADS-box transcription factors in orchardgrass, especially those involved in abiotic stress, have not yet been elucidated. Here, 123 DgMADS-box members were identified in orchardgrass and a detailed overview has been presented. Syntenic analysis indicated that the expansion of the DgMADS-box genes in orchardgrass is mainly dependent on tandem duplication events. Some DgMADS-box genes were induced by multiple abiotic stresses, indicating that these genes may play critical regulatory roles in orchardgrass response to various abiotic stresses. Heterologous expression showed that DgMADS114 and DgMADS115 could enhance stress tolerance of transgenic Arabidopsis, as revealed by longer root length or higher survival rates under PEG, NaCl, ABA, and heat stress. The results of this study provide a scientific basis for clarifying the functional characterization of MADS-box genes in orchardgrass in response to environmental stress can be further used to improve forages and crops via breeding programs.

METABOLISMS OF 13C IN CATTLE SEMITENDINOSUS MUSCLE AFTER ADMINISTRATION OF 13C LABELED ORCHARD GRASS.

14C released from nuclear facilities is transferred to cattle through their consumption of 14C contaminated grasses. To estimate the concentrations of 14C in their meat, we conducted two sets of experiments. In the first experiment, 230 mg of 13C per day was administered to cattle aged 10 months for 28 days in the form of 13C-labeled grass. The 13C concentration in the semitendinosus muscle decreased exponentially after reaching its peak value. The mean half-life was 76 ± 13 days. In the second experiment, 550 mg of 13C per day was administered to 24-month-old cattle. The change in the semitendinosus muscle was smaller than that recorded in the first experiment, even though the amount of 13C administered per body weight was slightly higher than that in the first experiment. Consequently, the half-life was not determined. Therefore, further studies are required to clarify the metabolism of carbon in 2-year-old cattle.

Genome-wide identification and characterization of bHLH family genes from orchardgrass and the functional characterization of DgbHLH46 and DgbHLH128 in drought and salt tolerance.

Basic helix-loop-helix (bHLH) is the second largest family of transcription factors that widely exist in plants and animals, and plays a key role in a variety of biological processes. As an important forage crop worldwide, little information is available about the bHLH family in orchardgrass (Dactylis glomerata L.), although a huge number of bHLH family have been identified and characterized in plants. In this study, we performed genome-wide analysis of bHLH transcription factor family of orchardgrass and identified 132 DgbHLH genes. The phylogenetic tree was constructed by using bHLH proteins of orchardgrass, with Arabidopsis thaliana and Oryza sativa bHLH proteins, to elucidate their homology and classify them into 22 subfamilies. The results of conserved motifs and gene structure support the classification of DgbHLH family. In addition, chromosomal location and gene duplication events of DgbHLH genes were further studied. Transcriptome data exhibited that DgbHLH genes were differentially expressed in different tissues of orchardgrass. We analyzed the gene expression level of 12 DgbHLH genes in orchardgrass under three types of abiotic stresses (heat, salt, and drought). Finally, heterologous expression assays in yeast indicated that DgbHLH46 and DgbHLH128 may enhance the resistance to drought and salt stress. Furthermore, DgbHLH128 may also be involved in abiotic stress by binding to the MYC element. Our study provides a comprehensive assessment of DgbHLH family of orchardgrass, revealing new insights for enhancing gene utilization and improving forage performance.

DNA hypermethylation promotes the flowering of orchardgrass during vernalization.

Vernalization, influenced by environmental factors, is an essential process associated with the productivity of temperate crops, during which epigenetic regulation of gene expression plays an important role. Although DNA methylation is one of the major epigenetic mechanisms associated with the control of gene expression, global changes in DNA methylation in the regulation of gene expression during vernalization-induced flowering of temperate plants remain largely undetermined. To characterize vernalization-associated DNA methylation dynamics, we performed whole-genome bisulfite-treated sequencing and transcriptome sequencing in orchardgrass (Dactylis glomerata) during vernalization. The results revealed that increased levels of genome DNA methylation during the early vernalization of orchardgrass were associated with transcriptional changes in DNA methyltransferase and demethylase genes. Upregulated expression of vernalization-related genes during early vernalization was attributable to an increase in mCHH in the promoter regions of these genes. Application of an exogenous DNA methylation accelerator or overexpression of orchardgrass NUCLEAR POLY(A) POLYMERASE (DgPAPS4) promoted earlier flowering, indicating that DNA hypermethylation plays an important role in vernalization-induced flowering. Collectively, our findings revealed that vernalization-induced hypermethylation is responsible for floral primordium initiation and development. These observations provide a theoretical foundation for further studies on the molecular mechanisms underlying the control of vernalization in temperate grasses.

Genome-wide identification of C2H2-type zinc finger gene family members and their expression during abiotic stress responses in orchardgrass (Dactylis glomerata).

The C2H2-type zinc finger protein (ZFP) family is one of the largest transcription factor families in the plant kingdom and its members are involved in plant growth, development, and stress responses. As an economically valuable perennial graminaceous forage crop, orchardgrass (Dactylis glomerata) is an important feedstuff resource owing to its high yield and quality. In this study, 125 C2H2-type ZFPs in orchardgrass (Dg-ZFPs) were identified and further classified by phylogenetic analysis. The members with similar gene structures were generally clustered into the same groups, with proteins containing the conserved QALGGH motif being concentrated in groups VIII and IX. Gene ontology and miRNA target analyses indicated that Dg-ZFPs likely perform diverse biological functions through their gene interactions. The RNA-seq data revealed differentially expressed genes across tissues and development phases, suggesting that some Dg-ZFPs might participate in growth and development regulation. Abiotic stress responses of Dg-ZFP genes were verified by qPCR and Saccharomyces cerevisiae transformation, revealing that Dg-ZFP125 could enhance the tolerance of yeasts to osmotic and salt stresses. Our study performed a novel systematic analysis of Dg-ZFPs in orchardgrass, providing a reference for this gene family in other grasses and revealing new insights for enhancing gene utilization.

Orchardgrass ACTIVATOR OF HSP90 ATPASE possesses autonomous chaperone properties and activates Hsp90 transcription to enhance thermotolerance.

High temperature stress is an environmental factor that negatively affects the growth and development of crops. Hsp90 (90 kDa heat shock protein) is a major molecular chaperone in eukaryotic cells, contributing to the maintenance of cell homeostasis through interaction with co-chaperones. Aha1 (activator of Hsp90 ATPase) is well known as a co-chaperone that activates ATPase activity of Hsp90 in mammals. However, biochemical and physiological evidence relating to Aha has not yet been identified in plants. In this study, we investigated the heat-tolerance function of orchardgrass (Dactylis glomerata L.) Aha (DgAha). Recombinant DgAha interacted with cytosolic DgHsp90s and efficiently protected substrates from thermal denaturation. Furthermore, heterologous expression of DgAha in yeast (Saccharomyces cerevisiae) cells and Arabidopsis (Arabidopsis thaliana) plants conferred thermotolerance in vivo. Enhanced expression of DgAha in Arabidopsis stimulates the transcription of Hsp90 under heat stress. Our data demonstrate that plant Aha plays a positive role in heat stress tolerance via chaperone properties and/or activation of Hsp90 to protect substrate proteins in plants from thermal injury.

Genome-wide identification, phylogenetic analysis, and expression analysis of the SPL gene family in orchardgrass (Dactylis glomerata L.).

SPL (SQUAMOSA promoter binding protein-like) is a plant-specific transcription factor family that contains the conserved SBP domain, which plays a vital role in the vegetative-to-reproductive phase transition, flowering development and regulation, tillering/branching, and stress responses. Although the SPL family has been identified and characterized in various plant species, limited information about it has been obtained in orchardgrass, which is a critical forage crop worldwide. In this study, 17 putative DgSPL genes were identified among seven chromosomes, and seven groups that share similar gene structures and conserved motifs were determined by phylogenetic analysis. Of these, eight genes have potential target sites for miR156. cis-Element and gene ontology annotation analysis indicated DgSPLs may be involved in regulating development and abiotic stress responses. The expression patterns of eight DgSPL genes at five developmental stages, in five tissues, and under three stress conditions were determined by RNA-seq and qRT-PCR. These assays indicated DgSPLs are involved in vegetative-to-reproductive phase transition, floral development, and stress responses. The transient expression analysis in tobacco and heterologous expression assays in yeast indicated that miR156-targeted DG1G01828.1 and DG0G01071.1 are nucleus-localized proteins, that may respond to drought, salt, and heat stress. Our study represents the first systematic analysis of the SPL family in orchardgrass. This research provides a comprehensive assessment of the DgSPL family, which lays the foundation for further examination of the role of miR156/DgSPL in regulating development and stress responses in forages grasses.

Directly quantifying multiple interacting influences on plant competition.

When plants compete what influences that interaction? To answer this we measured belowground competition directly, as the simultaneous capture of soil ammonium and nitrate by co-existing herbaceous perennials, Dactylis glomerata and Plantago lanceolata, under the influence of: species identity; N uptake and biomass of focal and neighbour plants; location (benign lowland versus harsher upland site); N availability (low or high N fertilizer); N ion, ammonium or nitrate production (mineralisation) rate, and competition type (intra- or interspecific), as direct effects or pairwise interactions in linear models. We also measured biomass as an indirect proxy for competition. Only three factors influenced both competitive N uptake and biomass production: focal species identity, N ion and the interaction between N ion and neighbour N uptake. Location had little effect on N uptake but a strong influence on biomass production. N uptake increased linearly with biomass only in isolated plants. Our results support the view that measuring resource capture or biomass production tells you different things about how competitors interact with one another and their environment, and that biomass is a longer-term integrative proxy for the outcomes of multiple separate interactions-such as competition for N-occurring between plants.

Genome-wide AP2/ERF gene family analysis reveals the classification, structure, expression profiles and potential function in orchardgrass (Dactylis glomerata).

The AP2/ERF transcription factor (TF) family is of great importance in developmental regulation and responses to stress and pathogenic stimuli. Orchardgrass (Dactylis glomerata), a perennial cold-season forage of high quality in the world's temperate zones, contributes to grazing land through mixed sowing with alfalfa (Medicago sativa) and white clover (Trifolium repens). However, little is known about AP2/ERF TFs in orchardgrass. In this study, 193 AP2/ERF genes were classified into five subfamilies and 13 subgroups through phylogenetic analysis. Chromosome structure analysis showed that AP2/ERF family genes in orchardgrass were distributed on seven chromosomes and specific conservative sequences were found in each subgroup. Exon-intron structure and motifs in the same subgroup were almost identical, and the unique motifs contributed to the classification and functional annotation of DgERFs. Expression analysis showed tissue-specific expression of DgERFs in roots and flowers, with most DgERFs widely expressed in roots. The expression levels of each subgroup (subgroups Vc, VIIa, VIIIb, IXa, and XIa) were high at the before-heading and heading stages (BH_DON and H_DON). In addition, 12 DgERFs in various tissues and five DgERFs associated with abiotic stresses were selected for qRT-PCR analysis showed that four dehydration-responsive element binding (DREB) genes and one ERF subfamily gene in orchardgrass were regulated with PEG, heat and salt stresses. DgERF056 belonged to ERF subfamily was involved in the processes of flowering and development stage. This study systematic explored the DgERFs at the genome level for the first time, which lays a foundation for a better understanding of AP2/ERF gene function in Dactylis glomerata and other types of forage.

Identification and Distribution of NBS-Encoding Resistance Genes of Dactylis glomerata L. and Its Expression Under Abiotic and Biotic Stress.

Orchardgrass (Dactylis glomerata L.) is drought resistant and tolerant to barren landscapes, making it one of the most important forages for animal husbandry, as well as ecological restoration of rocky landscapes that are undergoing desertification. However, orchardgrass is susceptible to rust, which can significantly reduce its yield and quality. Therefore, understanding the genes that underlie resistance against rust in orchardgrass is critical. The evolution, cloning of plant disease resistance genes, and the analysis of pathogenic bacteria induced expression patterns are important contents in the study of interaction between microorganisms and plants. Genes with nucleotide binding site (NBS) structure are disease-resistant genes ubiquitous in plants and play an important role in plant attacks against various pathogens. Using sequence analysis and re-annotation, we identified 413 NBS resistance genes in orchardgrass. Similar to previous studies, NBS resistance genes containing TIR (toll/interleukin-1 receptor) domain were not found in orchardgrass. The NBS resistance genes can be divided into four types: NBS (up to 264 homologous genes, accounting for 64% of the total number of NBS genes in orchardgrass), NBS-LRR, CC-NBS, and CC-NBS-LRR (minimum of 26 homologous genes, only 6% of the total number of NBS genes in orchardgrass). These 413 NBS resistance genes were unevenly distributed across seven chromosomes where chromosome 5 had up to 99 NBS resistance genes. There were 224 (54%) NBS resistance genes expressed in different tissues (roots, stems, leaves, flowers, and spikes), and we did not detect expression for 45 genes (11%). The remaining 145 (35%) were expressed in some tissues. And we found that 11 NBS resistance genes were differentially expressed under waterlogging stress, 5 NBS resistance genes were differentially expressed under waterlogging and drought stress, and 1 NBS resistance was is differentially expressed under waterlogging and heat stress. Most importantly, we found that 65 NBS resistance genes were significantly expressed in different control groups. On the 7th day of inoculation, 23 NBS resistance genes were differentially expressed in high resistance materials alone, of which 7 NBS resistance genes regulate the "plant-pathogen interaction" pathway by encoding RPM1. At the same time, 2 NBS resistance genes that were differentially expressed in the high resistance material after inoculation were also differentially expressed in abiotic stress. In summary, the NBS resistance gene plays a crucial role in the resistance of orchardgrass to rust.

Plant volatile emission depends on the species composition of the neighboring plant community.

BACKGROUND: Plants grow in multi-species communities rather than monocultures. Yet most studies on the emission of volatile organic compounds (VOCs) from plants in response to insect herbivore feeding focus on one plant species. Whether the presence and identity of neighboring plants or plant community attributes, such as plant species richness and plant species composition, affect the herbivore-induced VOC emission of a focal plant is poorly understood. METHODS: We established experimental plant communities in pots in the greenhouse where the focal plant species, red clover (Trifolium pratense), was grown in monoculture, in a two species mixture together with Geranium pratense or Dactylis glomerata, or in a mixture of all three species. We measured VOC emission of the focal plant and the entire plant community, with and without herbivory of Spodoptera littoralis caterpillars caged on one red clover individual within the communities. RESULTS: Herbivory increased VOC emission from red clover, and increasing plant species richness changed emissions of red clover and also from the entire plant community. Neighbor identity strongly affected red clover emission, with highest emission rates for plants growing together with D. glomerata. CONCLUSION: The results from this study indicate that the blend of VOCs perceived by host searching insects can be affected by plant-plant interactions.

Local plant responses to global problems: Dactylis glomerata responses to different traffic pollutants on roadsides.

The growing number of road vehicles is a major source of regional and global atmospheric pollution increasing concentrations of CO2 in the air, and levels of metals in air and soil. Nevertheless, the effects of these pollutants on plants growing at roadsides are poorly documented. We carried out an observational study of unmanipulated plants growing by the road, to identify the morpho-physiological responses in a perennial grass Dactylis glomerata. Firstly, we wanted to know the general effect of traffic intensity and ambient CO2 and its interactions on different plant traits. Accordingly, we analyzed the photosynthetic response by field A/Ci Response Curves, SLA, pigment pools, foliar nitrogen, carbohydrates and morphological traits in plants at three distances to the road. Secondly, we wanted to know if Dactylis glomerata plants can accumulate metals present on the roadside (Pb, Zn, Cu, and Sr) in their tissues and rhizosphere, and the effect of these metals on morphological traits. The MANCOVA whole model results shown: 1) a significant effect of road ambient CO2 concentration on morphological traits (not affected by traffic intensity, P interaction CO2 x traffic intensity>0.05), that was mainly driven by a significant negative relationship between the inflorescence number and ambient CO2; 2) a positive and significant relationship between ambient CO2 and the starch content in leaves (unaffected by traffic intensity); 3) a reduction in Jmax (electron transport rate) at high traffic intensity. These lines of evidences suggest a decreased photosynthetic capacity due to high traffic intensity and high levels of ambient CO2. In addition, Pb, Cu, Zn and Sr were detected in Dactylis glomerata tissues, and Cu accumulated in roots. Finally, we observed that Dactylis glomerata individuals growing at the roadside under high levels of CO2 and in the presence of metal pollutants, reduced their production of inflorescences.

Tracing the fate and transport of secondary plant metabolites in a laboratory mesocosm experiment by employing mass spectrometric imaging.

Mass spectrometric imaging (MSI) has received considerable attention in recent years, since it allows the molecular mapping of various compound classes, such as proteins, peptides, glycans, secondary metabolites, lipids, and drugs in animal, human, or plant tissue sections. In the present study, the application of laser-based MSI analysis of secondary plant metabolites to monitor their transport from the grass leaves of Dactylis glomerata, over the crop of the grasshopper Chorthippus dorsatus to its excrements, and finally in the soil solution is described. This plant-herbivore-soil pathway was investigated under controlled conditions by using laboratory mesocosms. From six targeted secondary plant metabolites (dehydroquinic acid, quinic acid, apigenin, luteolin, tricin, and rosmarinic acid), only quinic acid, and dehydroquinic acid, an in-source-decay (ISD) product of quinic acid, could be traced in nearly all compartments. The tentative identification of secondary plant metabolites was performed by MS/MS analysis of methanol extracts prepared from the investigated compartments, in both the positive and negative ion mode, and subsequently compared with the results generated from the reference standards. Except for tricin, all secondary metabolites could be tentatively identified by this approach. Additional liquid-chromatography mass spectrometry (LC-MS) experiments were carried out to verify the MSI results and revealed the presence of quinic acid only in grass and chewed grass, whereas apigenin-hexoside-pentoside and luteolin-hexoisde-pentoside could be traced in the grasshopper body and excrement extracts. In summary, the MSI technique shows a trade-off between sensitivity and spatial resolution. Graphical abstract Monitoring quinic acid in a mesocosm experiment by mass spectrometric imaging (MSI).

Water use efficiency and shoot biomass production under water limitation is negatively correlated to the discrimination against 13C in the C3 grasses Dactylis glomerata, Festuca arundinacea and Phalaris arundinacea.

Climate change impacts rainfall patterns which may lead to drought stress in rain-fed agricultural systems. Crops with higher drought tolerance are required on marginal land with low precipitation or on soils with low water retention used for biomass production. It is essential to obtain plant breeding tools, which can identify genotypes with improved drought tolerance and water use efficiency (WUE). In C3 plant species, the variation in discrimination against 13C (Δ13C) during photosynthesis has been shown to be a potential indicator for WUE, where discrimination against 13C and WUE were negatively correlated. The aim of this study was to determine the variation in the discrimination against 13C between species and cultivars of three perennial C3 grasses (Dactylis glomerata (cocksfoot), Festuca arundinacea (tall fescue) and Phalaris arundinacea (reed canary grass)) and test the relationships between discrimination against 13C, season-long water use WUEB, shoot and root biomass production in plants grown under well-watered and water-limited conditions. The grasses were grown in the greenhouse and exposed to two irrigation regimes, which corresponded to 25% and 60% water holding capacity, respectively. We found negative relationships between discrimination against 13C and WUEB and between discrimination against 13C and shoot biomass production, under both the well-watered and water-limited growth conditions (p < 0.001). Discrimination against 13C decreased in response to water limitation (p < 0.001). We found interspecific differences in the discrimination against 13C, WUEB, and shoot biomass production, where the cocksfoot cultivars showed lowest and the reed canary grass cultivars highest values of discrimination against 13C. Cocksfoot cultivars also showed highest WUEB, shoot biomass production and potential tolerance to water limitation. We conclude that discrimination against 13C appears to be a useful indicator, when selecting C3 grass crops for biomass production under drought conditions.

Use of two grasses for the phytoremediation of aqueous solutions polluted with terbuthylazine.

The capacity of two grasses, tall fescue (Festuca arundinacea) and orchardgrass (Dactylis glomerata), to remove terbuthylazine (TBA) from polluted solutions has been assessed in hydroponic cultures. Different TBA concentrations (0.06, 0.31, 0.62, and 1.24 mg/L) were chosen to test the capacity of the two grasses to resist the chemical. Aerial biomass, effective concentrations (to cause reductions of 10, 50, and 90% of plant aerial biomass) and chlorophylls contents of orchardgrass were found to be more affected. Tall fescue was found to be more capable of removing the TBA from the growth media. Furthermore, enzymes involved both in the herbicide detoxification and in the response to herbicide-induced oxidative stress were investigated. Glutathione S-transferase (GST, EC. 2.5.1.18) and ascorbate peroxidase (APX, EC. 1.11.1.11) of tall fescue were found to be unaffected by the chemical. GST and APX levels of orchardgrass were decreased by the treatment. These negative modulations exerted by the TBA on the enzyme of orchardgrass explained its lower capacity to cope with the negative effects of the TBA.

Divergent utilization patterns of grass fructan, inulin, and other nonfiber carbohydrates by ruminal microbes.

Fructans are an important nonfiber carbohydrate in cool season grasses. Their fermentation by ruminal microbes is not well described, though such information is needed to understand their nutritional value to ruminants. Our objective was to compare kinetics and product formation of orchardgrass fructan (phlein; PHL) to other nonfiber carbohydrates when fermented in vitro with mixed or pure culture ruminal microbes. Studies were carried out as randomized complete block designs. All rates given are first-order rate constants. With mixed ruminal microbes, rate of substrate disappearance tended to be greater for glucose (GLC) than for PHL and chicory fructan (inulin; INU), which tended to differ from each other (0.74, 0.62, and 0.33 h(-1), respectively). Disappearance of GLC had almost no lag time (0.04 h), whereas the fructans had lags of 1.4h. The maximum microbial N accumulation, a proxy for cell growth, tended to be 20% greater for PHL and INU than for GLC. The N accumulation rate for GLC (1.31h(-1)) was greater than for PHL (0.75 h(-1)) and INU (0.26 h(-1)), which also differed. More microbial glycogen (+57%) was accumulated from GLC than from PHL, though accumulation rates did not differ (1.95 and 1.44 h(-1), respectively); little glycogen accumulated from INU. Rates of organic acid formation were 0.80, 0.28, and 0.80 h(-1) for GLC, INU, and PHL, respectively, with PHL tending to be greater than INU. Lactic acid production was more than 7-fold greater for GLC than for the fructans. The ratio of microbial cell carbon to organic acid carbon tended to be greater for PHL (0.90) and INU (0.86) than for GLC (0.69), indicating a greater yield of cell mass per amount of substrate fermented with fructans. Reduced microbial yield for GLC may relate to the greater glycogen production that requires ATP, and lactate production that yields less ATP; together, these processes could have reduced ATP available for cell growth. Acetate molar proportion was less for GLC than for fructans, and less for PHL than for INU. In studies with pure cultures, all microbes evaluated showed differences in specific growth rate constants (µ) for GLC, fructose, sucrose, maltose, and PHL. Selenomonas ruminantium and Streptococcus bovis showed the highest µ for PHL (0.55 and 0.67 h(-1), respectively), which were 50 to 60% of the µ achieved for GLC. The 10 other species tested had µ between 0.01 and 0.11h(-1) with PHL. Ruminal microbes use PHL differently than they do GLC or INU.

Phytoremediation of Polycyclic Aromatic Hydrocarbons in Soils Artificially Polluted Using Plant-Associated-Endophytic Bacteria and Dactylis glomerata as the Bioremediation Plant.

The reaction of soil microorganisms to the contamination of soil artificially polluted with polycyclic aromatic hydrocarbons (PAHs) was evaluated in pot experiments. The plant used in the tests was cock's foot (Dactylis glomerata). Three different soils artificially contaminated with PAHs were applied in the studies. Three selected PAHs (anthracene, phenanthrene, and pyrene) were used at the doses of 100, 500, and 1000 mg/kg d.m. of soil and diesel fuel at the doses of 100, 500, and 1000 mg/kg d.m. of soil. For evaluation of the synergistic effect of nitrogen fixing bacteria, the following strains were selected: associative Azospirillum spp. and Pseudomonas stutzerii. Additionally, in the bioremediation process, the inoculation of plants with a mixture of the bacterial strains in the amount of 1 ml suspension per 500 g of soil was used. Chamber pot-tests were carried out in controlled conditions during four weeks of plant growth period. The basic physical, microbiological and biochemical properties in contaminated soils were determined. The obtained results showed a statistically important increase in the physical properties of soils polluted with PAHs and diesel fuel compared with the control and also an important decrease in the content of PAHs and heavy metals in soils inoculated with Azospirillum spp. and P. stutzeri after cock's foot grass growth. The bioremediation processes were especially intensive in calcareous rendzina soil artificially polluted with PAHs.

The effect of high polyphenol oxidase grass silage on metabolism of polyunsaturated fatty acids and nitrogen across the rumen of beef steers.

Polyphenol oxidase (PPO) activity in red clover (Trifolium pratense) has been reported to reduce both proteolysis and lipolysis, resulting in greater N use efficiency and protection of PUFA across the rumen. Although high levels of PPO have been reported in grasses such as cocksfoot (orchard grass; Dactylis glomerata), no in vivo research has determined whether grass PPO elicits the same response as red clover PPO. To test the hypothesis that silage ensiled from grass with high levels of PPO protects N and PUFA across the rumen, 6 steers with ruminal and duodenal cannulas were offered cocksfoot silage (CO; high-PPO grass), perennial ryegrass silage (PR; Lolium perenne; low-PPO grass), or red clover silage (RC; high-PPO control) at 16 g DM/kg BW daily with the experiment consisting of two 3 × 3 Latin squares with 21-d periods, consisting of 12 d of diet adaptation, 6 d of duodenal marker infusion, 2 d of duodenal sampling, and 1 d of ruminal sampling. All silages were well preserved, with DM of 34.4, 55.3, and 45.4% for CO, PR, and RC. Activity of PPO in silages was low due to deactivation but was greater in CO than either PR or RC (0.15 vs. 0.05 and 0.08 µkatal/g DM). Protein-bound phenol (mg/g DM) as a measure of the degree of oxidation and an indication of PPO protection was greatest for RC (15.9) but comparable for PR (10.1) and CO (12.2). Biohydrogenation of C18 PUFA was significantly lower on RC compared to the 2 grass silages with CO greater than PR. Despite lower levels of total fatty acid intake and subsequent duodenal flow, CO resulted in greater levels of phytanic acid and total branched and odd chain fatty acids in duodenal digesta than RC or PR. Ruminal ammonia concentration was greatest for RC, with no difference between the grasses. Duodenal flow of microbial N and efficiency of microbial protein synthesis were lowest for CO and comparable for RC and PR. The CO (high-grass PPO) did not result in elevated levels of C18 PUFA escaping the rumen or improve efficiency of total N transfer through the rumen compared to PR. The RC resulted in a greater flow of N and nonmicrobial N to the duodenum than the 2 grasses with PR greater than CO.

Efficacy of biosolids in assisted phytostabilization of metalliferous acidic sandy soils with five grass species.

The role of sewage sludge as an immobilising agent in the phytostabilization of metal-contaminated soil was evaluated using five grass species viz., Dactylis glomerata L., Festuca arundinacea Schreb., F. rubra L., Lolium perenne L., L. westerwoldicum L. The function of metal immobilization was investigated by monitoring pH, Eh and Cd, Pb, and Zn levels in column experiment over a period of 5-months. Grasses grown on sewage sludge-amendments produced high biomass in comparison to controls. A significant reduction in metal uptake by plants was also observed as a result of sewage sludge application, which was attributed to decreased bioavailability through soil stabilisation. We have observed that the sludge amendment decreased metal bioavailability and concentrations in soil at a depth of 25 cm, in contrast to untreated columns, where metal concentrations in the soil solution were very high.