Effect of phosphorus supplementation on growth, nutrient uptake, physiological responses, and cadmium absorption by tall fescue (Festuca arundinacea Schreb.) exposed to cadmium

Cadmium is a common heavy metal pollutant. In some plants, its absorption is inhibited by exogenous phosphorus. Here, the effect of P supplementation on the growth of tall fescue exposed to Cd was evaluated in a hydroponic culture experiment. Plants were exposed to five concentrations of P (0, 0.25, 0.5, 0.75, and 1.0 mmol L^-1) and three concentrations of Cd (50, 100, and 150 mg L^-1), and plant growth, Cd content, absorption, physiological characteristics, and nutrient accumulation were investigated. P supplementation significantly reduced the Cd content, Cd translocation factor (TF), Cd removal efficiency, plant P absorption, chlorophyll content, glutathione levels, glutathione reductase levels, and superoxide dismutase (SOD) activity in tall fescue under Cd stress (P < 0.05). Moreover, it increased the vertical growth rate and biomass of tall fescue. At a constant P concentration, the biomass and vertical growth rate significantly decreased with an increasing Cd concentration, and the shoot Cd content, SOD activity, and TF significantly increased (P < 0.05). High P supplementation (0.75 and 1.0 mmol L^-1) ameliorated the damage caused by 150 mg L^-1 Cd stress, and the biomass, vertical shoot and vertical root growth rates were increased by 72.06-82.06%, 250.00-316.67%, 300.00-312.00%, respectively. In the plants subjected to 50 mg L^-1 Cd stress, 0.5 mmol L^-1 P supplementation enhanced biomass, vertical shoot and vertical root growth rates by 29.99%, 20.41%, and 21.43%, respectively, and reduced the Cd content in shoots (45.85%) and roots (9.71%). Except for the total potassium content and catalase activity, different concentrations of Cd negatively affected all parameters tested. Such negative effects were limited by P supplementation. Optimizing the nutrient composition and concentrations could minimize the potential negative impacts of Cd on plant growth.

Comparative study of alleviation effects of DMTU and PCIB on root growth inhibition in two tall fescue varieties under cadmium stress

In plants, tolerance to cadmium (Cd) stress is closely related to indole-3-acetic acid (IAA) and hydrogen peroxide (H₂O₂). However, it is unclear whether Cd-resistant and -sensitive varieties respond differently to Cd stress. In this study, the effects of dimethylthiourea (DMTU, a H₂O₂ scavenger) and p-chlorophenoxy isobutyric acid (PCIB, an IAA signaling inhibitor) on root growth, endogenous hormones and antioxidant system were investigated to decipher how DMTU and PCIB treatments alleviate the inhibition of root elongation in Cd-resistant (Commander) and -sensitive (Crossfire III) tall fescue varieties under Cd stress. Both varieties subjected to 10 μM Cd treatments for 12 h presented a substantial decrease in root elongation coupled with a reduction in brassinosteroid (BR) and zeatin riboside (ZR) contents, but the changes in IAA and abscisic acid (ABA) contents under Cd stress were opposite in the two varieties. In addition, the H₂O₂ content and antioxidant enzyme activities significantly increased in both varieties. However, pretreatment with PCIB or DMTU mitigated the inhibition of root elongation caused by Cd, accompanied by the significant changes of aforementioned physiological parameters. PCIB significantly reduced the IAA content in 'Commander', while DMTU significantly increased the IAA content in 'Crossfire III' and effectively relieved the inhibition of root elongation. But both treatments decreased the Cd-induced H₂O₂ accumulation. These results indicated that DMTU or PCIB can alleviate the Cd-inhibited root elongation in two varieties whose resistance differed under Cd stress, but they presented differences in the response of hormones, especially IAA, which may be due to the different adaptation mechanisms of two varieties in response to Cd stress.

Evaluation of seed nitrate assimilation and stimulation of phenolic-linked antioxidant on pentose phosphate pathway and nitrate reduction in three feed-plant species

BACKGROUND

Soil and water pollution due to nitrate are becoming increasingly serious worldwide. The government also put forward relevant governance policies, and a large number of scholars studied chemical physics and other methods to remove nitrate in water, but the cost was substantial. Studies have found that planting systems including grasses have the potential to remove nitrates. However, there are few studies on nitrate linked pathway and nitrate assimilation during its early growth.

RESULTS

We have evaluated three different feed-plant species with three levels of overnight seed nitrate treatments along with a control. The activity of different enzymes from 2 weeks old shoots was measured to get a comprehension of proline-associated pentose phosphate pathway coupled with nitrate assimilation and phenolic-linked antioxidant response system in these species under nitrate treatments. All three feed-plant species showed high nitrate tolerance during germination and early growth stages. It is perceived that the accumulation of total soluble phenolics and total antioxidant activity was high in all three feed-plant species under high nitrate treatments. In terms of high G6PDH activity along with low SDH activity in alfalfa, there may be a shift of carbon flux in this species under high nitrate treatments. Higher activity of these enzymes along with higher SOD and GPX activity was observed in alfalfa. The efficient mechanism of nitrate stress tolerance of alfalfa also correlated with higher photochemical efficiency. Perennial ryegrass also showed excellent potential under high nitrate treatments by adopting an efficient mechanism to counter nitrate-induced oxidative stress.

CONCLUSIONS

Under the condition of nitrate treatment, the germination rates of the three feed-plant species are still ideal, and they have good enzyme activity and have the potential to remove nitrate.

Application of Festuca arundinacea in phytoremediation of soils contaminated with Pb, Ni, Cd and petroleum hydrocarbons

Phytoremediation is a promising "green technique" used to purify contaminated soils. The performed phytoremediation experiments assisted by the fertilization process involving pots of F.arundinacea grown on soils with diverse concentrations and types of contaminations produced the following decreased percentages after 6 months: Pb (25.4-34.1%), Ni (18.7-23.8%), Cd (26.3-46.7%), TPH (49.4-60.1%). Primarily, TPH biodegradation was occurring as a result of basic bioremediation stimulated by adding optimal volumes of biogenic substances and corrections in the soil reaction, while phytoremediation improved this process by 17.4 - 23.1%. The highest drop in a range of 45.6 - 55.5% was recorded for the group of C₁₂-C₁₈ hydrocarbons, with the lowest one for C₂₅-C₃₆, amounting to 9.1-17.4%. Translocation factor values were: TF<1 and ranged, respectively, for: Pb (0.46-0.53), Ni (0.29-0.33), and Cd (0.21-0.25), which indicate that heavy metals absorbed by Festuca arundinacea they mainly accumulated in the root of the tissue in descending order: Cd <Ni <Pb, showing poor metal translocation from roots to shoots. Co-occurrence of petroleum pollutants (TPH) in contaminated (Pb, Cd, Ni) soils results in reducing their contents in Festuca arundinacea roots. The process of phytoremediation of contaminated soil using F.arundinacea assisted with fertilization was monitored by means of toxicological tests: Microtox SPT (inhibition of the luminescence of V. fischeri), Ostracodtoxkit F (mortality, growth inhibition Heterocypris incongruens) and MARA (growth of 11 microorganisms) and Phytotoxkit F (germination assessment, inhibition root growth: Sorghum saccharatum, Lepidium sativum and Sinapis alba). The sensitivity of toxicological tests used was comparable and increased in the order: MARA<Ostracodtoxkit<Microtox. The performed phytotoxicity tests have indicated variable sensitivity of the tested plants on contaminants occurring in the studied soils, following the sequence: L. Sativum<S. saccharatum<S. alba. The obtained results indicate a decrease in soil toxicity during phytoremediation assisted by the fertilization process using Festuca arundinacea, which correlates with a decrease in the amount of harmful impurities contained in soils subjected to phytoremediation.

Lead-induced oxidative stress triggers root cell wall remodeling and increases lead absorption through esterification of cell wall polysaccharide

Tall fescue (Festuca arundinacea Schreb) shows remarkable tolerance to lead (Pb), but the mechanisms involved in metal tolerance are not yet well understood. Here, tall fescue were firstly cultivated hydroponically with Pb²⁺ (0, 50, 200 and 1000 mg/L) for 14 days. The results showed that remodeling of root architecture plays important roles in tolerance of tall fescue to Pb²⁺ stress. Increased cell wall (CW) components contribute to restrict high amount of Pb²⁺ in roots. Additionally, the uronic acid contents of pectin, hemicellulose 1 (HC1) and hemicellulose 2 (HC2) increased under Pb²⁺ stress. We further observed that tall fescue cultivated with H₂O₂ showed similar remodeling of root architecture as Pb²⁺ treatment. Furthermore, pectin, HC1 and HC2 fractions were sequentially extracted from 0 and 10 mM H₂O₂ treated roots, and Pb²⁺ adsorption capacity and contents of carboxyl groups of pectin and HC2 fractions were steadily increased under H₂O₂ treatment in vitro. Our results suggest that degrees of esterification of pectin and HC2 are regulated by H₂O₂. High amount of low-esterified pectin and HC2 offer more carboxyl groups, provide more Pb²⁺ binding sites, and restrict more Pb²⁺ in the CW, which may enhance tolerance of tall fescue to Pb²⁺ stress.

Effect of 24-epibrassinolide on reactive oxygen species and antioxidative defense systems in tall fescue plants under lead stress

Lead is one of the most hazardous pollutants to both the environment as well as human beings. As one of the approaches to enhance phytoremediation, brassinosteroids are predicted as a potential candidate phytohormone for assisted phytoremediation. Few studies have focused on the physiological regulations of tall fescue plants (Festuca arundinacea Schreb.), a potential phytoremediation species, for its responses to applications of brassinosteroids under lead stress. Therefore, the objectives of this study were to investigate the effects of foliar application of 24-epibrassinolide, a brassinosteroids analogue, on reactive oxygen species accumulation and antioxidative defense systems of tall fescue when exposed to lead, and ultimately its potential to be used in phytoremediation. When exposed to lead (1000 mg/kg) for 80 d, decreases in shoot and root biomass of tall fescue biomass as well as chlorophyll and carotenoid productions were found. Foliar application of 24-epibrassinolide at three rates and five applications every 7 d improved the biomass of both shoots and roots, and increased the photosynthetic pigments. The improved lead tolerance in tall fescue plants after 24-epibrassinolide applications was associated with reduced H₂O₂ and O₂^.- accumulations and increased antioxidative enzyme activities including superoxide dismutase, catalase, and guaiacol peroxidase. Additionally, osmoprotectants increased and lipid peroxidation decreased. Ultimately, foliar applications of 24-epibrassinolide enhanced the lead recovery rate of tall fescue plants, proving its potential role in phytoremediation for soil contaminated with heavy metals such as lead.

Interactions between decabromodiphenyl ether and lead in soil-plant system

Pot experiments were conducted under abiotic conditions to investigate the interactive influence of decabromodiphenyl ether (BDE-209) and lead (Pb) on the seed germination, germ length, root exudation and physiological characteristics of tall fescue (Festuca arundinaceae), and the uptake, accumulation of Pb and BDE-209 in the plant tissues. Results show that seed germination and germ length were impacted by Pb but less influenced by BDE-209. BDE-209 spiking (10 and 50 mg/L) could alleviate the toxicity of high Pb concentration on seed germination and growth. The chlorophyll content was significantly increased at 500 mg/kg Pb but declined at 2000 mg/kg Pb. Low-level Pb contamination (500 mg/kg) activated antioxidase activity; however, 2000 mg/kg Pb significantly reduced the antioxidase activity. Plant biomass slightly decreased at 500 mg/kg Pb but significantly declined at 2000 mg/kg Pb. The addition of a moderate dosage of BDE-209 (10-50 mg/kg) lessened Pb phytotoxicity, leading to improved plant growth relative to the case of Pb spiking alone. The exudate secretion was significantly enhanced by Pb addition, but BDE-209 spiking only caused slightly increased secretion. Pb could interfere with BDE-209 adsorption and translocation of tall fescue by affecting physiological behavior of the plant, but BDE-209 exhibited little influence on the Pb fate in the plant. Overall, BDE-209 had slight interference on the impact of Pb towards tall fescue. The results demonstrate the complex interactive effects of organic pollutants and heavy metals in the soil-plant system.

The evaluation of resistance to Co 2+ of lawn plant at seedling stage and its concentration property at adult stage

In order to evaluate the resistance of lawn plant to Co²⁺ at germination stage and discuss its concentration property at adult stage, four kinds of lawn plant which have some growth advantages in Co²⁺ polluted environment were selected as experimental materials in this research. They are tall fescue, timothy grass, inflorescences, and annual ryegrass. The results show that the evaluation of resistance to Co²⁺ of tall fescue's seed is the highest; the evaluation of resistance to Co²⁺ of annual ryegrass seed is the lowest. The low consistence Co²⁺ could improve the seed germination. With Co²⁺ concentration increase, the accumulation coefficient of four plants increased at first and decreased later; the accumulation coefficient of underground portion is higher than the accumulation coefficient of aboveground; with Co²⁺ concentration increase, the transfer coefficient of four plants have a remarkable decline. In these plants, the accumulation coefficient of tall fescue and annual ryegrass is bigger than other two plants. As the concentration of Co²⁺ treatment increased to 100 mg/kg, the aboveground enrichment of Co²⁺ in F. elata reached 75 mg/kg, followed by L. multiflorum (68.9 mg/kg), P. pratense (48.8 mg/kg), and D. glomerata (27.2 mg/kg).The highest underground enrichment of Co²⁺ in F. elata reached 836.46 mg/kg, in contrast to the lowest underground enrichment in D. glomerata, 264.67 mg/kg. It shows that fescue and annual ryegrass have a better enrichment property to Co²⁺ and have a better prospect for the treatment of cobalt-contaminated soil. This research could provide some scientific basis and main technical approach for the soil contaminated by Co²⁺.

Plant toxicity and accumulation of biosolids-borne ciprofloxacin and azithromycin

Trace organic chemicals (TOrCs) in land applied biosolids can cause phytotoxicities and contaminate human and animal food chains. Information on phytotoxicity and phytoaccumulation of environmentally relevant concentrations of two antibiotic TOrCs, ciprofloxacin (CIP) and azithromycin (AZ), from biosolids-amended soils is limited. Greenhouse studies were conducted to assess the plant toxicity and accumulation of a range of environmentally relevant concentrations of biosolids-borne CIP and AZ in biosolids-amended soils. Separate studies assessed phytotoxicity potential of soil-borne CIP and AZ (soils directly spiked with the target antibiotics without biosolids) at concentrations much greater than those of environmental relevance in biosolids-amended soils. Both the biosolids-borne and the soil-borne antibiotic studies involved three plants (radish (Raphanus sativus), lettuce (Lactuca sativa), and tall fescue grass (Festuca arundinacea)) of different morphologies, physiologies, and chemical exposure scenarios. Phytotoxicity and phytoaccumulation from the biosolids-borne antibiotics were minimal at environmentally relevant concentrations, even in sand. The separate phytotoxicity experiments involving the soil-borne antibiotics revealed no observed adverse effect concentration (NOAEC) of 3.2 mg kg-1 (AZ) and 36.1 mg kg-1 (CIP) for the three plants grown in soils mimicking typical agricultural soils. These NOAEC values are about 100-fold greater than the antibiotic concentrations expected in biosolids-amended soils. NOAEC values under an unrealistic worst-case where the antibiotics were directly spiked to sand (NOAEC = 3.2 mg kg-1 for AZ; and ≥0.36 mg kg-1 for CIP) were also greater than the environmentally relevant concentrations of the biosolids-borne antibiotics. The results suggest that land application of biosolids-borne CIP and AZ pose De minimis risks to plants. Point estimates of plant bioaccumulation factors (dry weight basis) were 0.01 (CIP) and 0.1 (AZ), suggesting minimal impacts of the target TOrCs on human and/or animal food chains.

Nitric oxide alleviates toxicity of hexavalent chromium on tall fescue and improves performance of photosystem II

Tall fescue (Festuca arundinacea Schreb) was widely studied for phytoremediation of organic or heavy metal contaminated soils. However, there is still little information concerning toxicity of chromium (Cr) to tall fescue and roles of nitric oxide (NO) in plants against Cr(VI) stress. In this study, different Cr(VI) treatments (0, 1, 5 and 10 mg/L Cr(VI)) and NO treatments were applied with different combinations in hydroponics culture and their interactions to tall fescue were studied. Specifically, 100 µM sodium nitroprusside (SNP) and 100 µM N^G-nitro-L-arginine-methyl ester (L-NAME) treatments were used to apply exogenous NO or inhibit synthesis of NO respectively. Our results showed that tall fescue exhibits comparable Cr(VI) tolerance as wheat (Triticum aestivum L.). Additionally, Cr(VI) accumulation in tall fescue leaves were carefully studied and discussed. Moreover, we observed the significantly increased reactive oxygen species (ROS) contents of tall fescue when subjected to Cr(VI) stress, as well as decreased photosynthetic activities induced by Cr(VI) stress by methods of chlorophyll a fluorescence transient, slow chlorophyll fluorescence kinetics and rapid light response curves. Decreased behaviors of photosynthetic activities may due to destruction of antennae pigments by Cr(VI), ROS burst induced by Cr(VI), and down regulation of photosystem II (PSII) by non-photochemical quenching to avoid over reduction of quinone A, which could be considered as an important strategy to cope with Cr(VI) stress. Meanwhile, exogenous NO treatment improves overall physiological and photosynthetic behaviors of tall fescue against Cr(VI) stress. Moreover, increased translocation factors and improved Cr(VI) tolerance of plants under exogenous NO treatment suggest that SNP treatment could be a useful application for Cr phytoremediation.

Distribution and phytotoxicity of soil labile aluminum fractions and aluminum species in soil water extracts and their effects on tall fescue

Soil acidification can alter the biogeochemistry of ecosystems and adversely affect biota; however, there are still many debates about the toxicity of aluminum (Al) fractions and Al species in soil:water extracts to plants. In this study, five crude soils with different pH values (4.92-8.51) were collected, seeded with tall fescue and grown in rhizosphere boxes for 120 days. Then, soil properties, labile Al fractions and Al species in soil:water extracts were determined, and their toxicities to plants were analyzed. Our study showed that a stable exchangeable Al fraction (ExAl) pool exists and is supplied by other labile Al fractions. Dissolution of Al from adsorbed hydroxyl-Al fraction (HyAl) and organic-Al fraction (OrAl) may play important roles in soil Al toxicity, as HyAl and OrAl account for major parts of soil labile Al. Additionally, Al³⁺ and mononuclear hydroxyl-Al species in soil:water extracts have few effects to plants. Nevertheless, high negative correlations were found between Al-F^- complexes and tall fescue biomass, indicating their toxicity in the natural soil environment. Thus, in many cases, Al³⁺ toxicity should not be emphasized because of its lower activity in soil water extracts. Moreover, toxicities of AlF₃(aq) and AlF₄^- to plants should be emphasized, because they have been confirmed in soil water extracts in this study.

Transcriptome analysis providing novel insights for Cd-resistant tall fescue responses to Cd stress

Cadmium (Cd) is a severely toxic heavy metal and environmental pollutant. Tall fescue is a cold season turf grass which has high resistance to Cd as well as the ability to enrich it. To investigate the molecular mechanism underlying the adaptability of tall fescue to Cd stress, RNA-Seq was used to examine Cd stress responses of tall fescue at a transcriptional level. A total of 12 cDNA libraries were constructed from the total RNA of roots or leaves of tall fescue with or without Cd treatments. A total of 2594 (1768 up- and 826 down-regulated) differentially expressed genes (DEGs) were detected in the roots of Cd-stressed tall fescue compared with control roots (R_cd vs R_ck), while only 52 (29 up- and 23 down-regulated) DEGs were found in the leaves of Cd-stressed plants versus the controls (L_cd vs L_ck). The genes encoding glutathione S-transferase (GST), transporter proteins including the ABC transporter, ZRT/IRT-like protein, potassium transporter/channel, nitrate transporter, putative iron-phytosiderophore transporter, copper-transporting ATPase or transporter and multidrug and toxic compound extrusion (MATE) proteins, and numerous transcription factors were found to be significantly induced in Cd-treated roots. In addition, pathogenesis/disease-related gene mRNAs were accumulated in Cd-treated roots of tall fescue. Furthermore, the significantly enriched KEGG pathways in roots were related to 'Glutathione metabolism', 'Ribosome', 'alpha-Linolenic acid metabolism', 'Diterpenoid biosynthesis', 'Sulfur metabolism', 'Phenylpropanoid biosynthesis', 'Protein processing in endoplasmic reticulum', 'Protein export' and 'Nitrogen metabolism'. The study provides novel insights for further understanding the molecular mechanisms of tall fescue responses to Cd stress.

Effect of single and mixed polycyclic aromatic hydrocarbon contamination on plant biomass yield and PAH dissipation during phytoremediation

Polycyclic aromatic hydrocarbon (PAH)-contaminated sites have a mixture of PAH of varying concentration which may affect PAH dissipation differently to contamination with a single PAH. In this study, pot experiments investigated the impact of PAH contamination on Medicago sativa, Lolium perenne, and Festuca arundinacea biomass and PAH dissipation from soils spiked with phenanthrene (Phe), fluoranthene (Flu), and benzo[a]pyrene (B[a]P) in single and mixed treatments. Stimulatory or inhibitory effects of PAH contamination on plant biomass yields were not different for the single and mixed PAH treatments. Results showed significant effect of PAH treatments on plant growth with an increased root biomass yield for F. arundinacea in the Phe (175%) and Flu (86%) treatments and a root biomass decrease in the mixed treatment (4%). The mean residual PAHs in the planted treatments and unplanted control for the single treatments were not significantly different. B[a]P dissipation was enhanced for single and mixed treatments (71-72%) with F. arundinacea compared to the unplanted control (24-50%). On the other hand, B[a]P dissipation was inhibited with L. perenne (6%) in the single treatment and M. sativa (11%) and L. perenne (29%) in the mixed treatment. Abiotic processes had greater contribution to PAH dissipation compared to rhizodegradation in both treatments. In most cases, a stimulatory effect of PAH contamination on plant biomass yield without an enhancement of PAH dissipation was observed. Plant species among other factors affect the relative contribution of PAH dissipation mechanisms during phytoremediation. These factors determine the effectiveness and suitability of phytoremediation as a remedial strategy for PAH-contaminated sites. Further studies on impact of PAH contamination, plant selection, and rhizosphere activities on soil microbial community structure and remediation outcome are required.

Differential effects of citric acid on cadmium uptake and accumulation between tall fescue and Kentucky bluegrass

Organic acids play an important role in cadmium availability, uptake, translocation, and detoxification. A sand culture experiment was designed to investigate the effects of citric acid on Cd uptake, translocation, and accumulation in tall fescue and Kentucky bluegrass. The results showed that two grass species presented different Cd chemical forms, organic acid components and amount in roots. The dormant Cd accumulated in roots of tall fescue was the pectate- and protein- integrated form, which contributed by 84.85%. However, in Kentucky bluegrass, the pectate- and protein- integrated Cd was only contributed by 35.78%, and the higher proportion of Cd form was the water soluble Cd-organic acid complexes. In tall fescue, citric acid dramatically enhanced 2.8 fold of Cd uptake, 3 fold of root Cd accumulation, and 2.3 fold of shoot Cd accumulation. In Kentucky bluegrass, citric acid promoted Cd accumulation in roots, but significantly decreased Cd accumulation in shoots. These results suggested that the enhancements of citric acid on Cd uptake, translocation, and accumulation in tall fescue was associated with its promotion of organic acids and the water soluble Cd-organic acid complexes in roots.

Toxic effects of cadmium on tall fescue and different responses of the photosynthetic activities in the photosystem electron donor and acceptor sides

Tall fescue (Festuca arundinacea Schreb) is a turf grass species which is widely used for rhizoremediation of organic contaminants and shows notable prospects in heavy metal phytoremediation. In this study, different concentrations of cadmium ion (Cd2+) were applied to study toxic effects of Cd2+ and responses of tall fescue by soilless culture. Tall fescue showed comparable high tolerance to Cd2+ as Indian mustard (Brassica juncea L.). Additionally, the treatment with high concentration of Cd2+ leaded to decreased chlorophyll contents, production of reactive oxygen species (ROS) and lipid peroxidation, as well as damage of cell membrane, necrosis and apoptosis in tall fescue roots, and toxicity of Cd2+ on physiologic properties of tall fescue has been well discussed. Moreover, in photosystem II electron donor side, electron transport from oxygen evolution complex (OEC) to Yz residue of D1 protein was inhibited under high Cd2+ treatments, which may be due to the Cd2+ induced ROS production and the replacement of Ca2+ in the core of OEC. In electron acceptor side, electron transport efficiency from quinone B to photosystem I acceptors increased under high Cd2+ treatments, which may be an important response for plants against Cd2+ toxicity and its mechanism needs our further study.

Plant reproduction is altered by simulated herbicide drift to constructed plant communities

Herbicide drift may have unintended impacts on native vegetation, adversely affecting individual species and plant communities. To determine the potential ecological effects of herbicide drift, small plant community plots were constructed using 9 perennial species found in different Willamette Valley (OR, USA) grassland habitats. Studies were conducted at 2 Oregon State University (Corvallis, OR, USA) farms in 2 separate years, with single and combined treatments of 0.01 to 0.2× field application rates (f.a.r.) of 1119 g ha-1 for glyphosate (active ingredient [a.i.] of 830 g ha-1 acid glyphosate) and 560 g ha-1 a.i. for dicamba. Plant responses were percentage of cover, number of reproductive structures, mature and immature seed production, and vegetative biomass. Herbicide effects differed with species, year, and, to a lesser extent, farm. Generally, 0.1 to 0.2× f.a.r. of the herbicides were required to affect reproduction in Camassia leichtlinii, Elymus glaucus, Eriophyllum lanatum, Festuca idahoensis, Iris tenax, and Prunella vulgaris. Eriophyllum lanatum also had a significant increase in percentage of immature seed dry weight with 0.01× f.a.r. of dicamba or the combination of glyphosate plus dicamba. Other species showed similar trends, but fewer significant responses. These studies indicated potential effects of low levels of herbicides on reproduction of native plants, and demonstrated a protocol whereby species growing in a constructed plant community can be evaluated for ecological responses. Environ Toxicol Chem 2017;36:2799-2813. Published 2017 SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

The advantages of endophyte-infected over uninfected tall fescue in the growth and pathogen resistance are counteracted by elevated CO2

Atmospheric CO2 concentrations are predicted to double within the next century. Despite this trend, the extent and mechanisms through which elevated CO2 affects grass-endophyte symbionts remain uncertain. In the present study, the growth, chemical composition and pathogen resistance of endophyte-infected (E+) and uninfected (E-) tall fescue were compared under elevated CO2 conditions. The results showed that the effect of endophyte infection on the growth of tall fescue was significantly affected by elevated CO2. Significant advantage of E+ over E- tall fescue in tiller number, maximum net photosynthetic rate and shoot biomass occurred only under ambient CO2. With CO2 concentration elevated, the beneficial effect of endophyte infection on the growth disappeared. Similarly, endophyte infection reduced lesion number and spore concentration of Curvularia lunata only under ambient CO2. These results suggest that the beneficial effect of endophyte infection on the growth and pathogen resistance of tall fescue could be counteracted by elevated CO2. An explanation for the counteraction may be found in a change in photosynthesis and nutritive quality of leaf tissue.

Effects of untreated and treated wastewater at the morphological, physiological and biochemical levels on seed germination and development of sorghum (Sorghum bicolor (L.) Moench), alfalfa (Medicago sativa L.) and fescue (Festuca arundinacea Schreb.)

Wastewater reuse in agriculture may help mitigate water scarcity. This may be reached if high quality treatments removing harmful pollutants are applied. The aim of the present study was to compare the effect of untreated (UTW) and treated wastewater (TW) on germination and seedlings development of alfalfa (Medicago sativa L.), fescue (Festuca arundinacea Schreb.) and sorghum (Sorghum bicolor (L.) Moench). UTW presented high turbidity (130 NTU), chemical and biological oxygen demand (COD, 719mgL^-1, BOD_5, 291mgL^-1) and metal concentrations. These levels caused mortality (18% for fescue), decreased germination speed in seeds (37.5% for alfalfa) and reductions of root and stem length in seedlings (80% and 22% respectively for alfalfa). Adverse effects on seeds germination were reflected at the biochemical level by increased H₂O₂ levels (6 times for sorghum after 5days) and by increased Malondialdehyde (MDA) levels (more than 600 times for sorghum roots) during seedlings development. When TW was used, these parameters were close to control seeds ones. They were also dependent on plant species and developmental stage. Therefore, for efficient reclaimed wastewater reuse in irrigation, suitable crops, displaying wide tolerance to toxic contents during germination and later seedling development stages have to be selected.

Flavonolignans from Elymus natans L. and Phytotoxic Activities

Elymus natans, a perennial gramineous grass, plays an important role in animal husbandry and environmental sustenance in the Qinghai-Tibet plateau as a result of its high forage quality and good adaptability to the local environment. A bioassay showed that the extracts of green grasses of E. natans (GG) exhibited stronger phytotoxic activities than withered grasses (WG) against crops and grasses. In view of the secondary metabolites, which may be responsible for the resistance of the plant, the chemical components of GG were investigated. The flavone tricin, E1, and 10 flavonolignans, E2-E11, including three new flavonolignans, E2, E10, and E11, were isolated and identified. As far as we know, this is the first report on the chemical constitutions of the plant until now. The contents of compounds E1 and E4-E7 in GG were significantly higher than those in WG in high-performance liquid chromatography analysis, and they also showed observably phytotoxic activities against lettuce and Festuca arundinacea.

Use of radiometric indices to evaluate Zn and Pb stress in two grass species (Festuca rubra L. and Vulpia myuros L.)

Vegetation indices obtained from radiometric measurements have been used to estimate the stress response of plants grown in contaminated sites. The phytotoxicity of Pb and Zn in Festuca rubra L. and Vulpia myuros L. plants grown under hydroponic conditions was evaluated using vegetation indices obtained from radiometric measurements. The plants were supplied with 3 mM Zn (+Zn), 500 μM Pb (+Pb) and 500 μM Pb with EDTA (+PbEDTA) for 3 months. Significantly higher Zn concentrations in F. rubra shoots compared with V. myuros shoots were detected for Zn and Pb treatments. EDTA increased Pb transport to the shoots for both grasses, while Pb-treated plants retained Pb primarily in the roots. All vegetation indices tested showed the highest differences in F. rubra under +PbEDTA treatment and minor effects under +Zn, whereas the major variations for V. myuros corresponded to +Zn treatment, followed by +PbEDTA. Red edge normalized difference vegetation index, yellowness index and anthocyanin concentration index were the most sensitive indices to report Zn and Pb phytotoxicity in these grasses. According to the results obtained, both metal concentrations and radiometric indices suggested that Pb is more phytotoxic to F. rubra, which tolerates high Zn levels, whereas V. myuros was strongly affected by high Zn levels and markedly tolerant to Pb, even when applied in a mobile form (PbEDTA). Both species could be used in the phytostabilization of Zn- and Pb-contaminated soils. The abilities of F. rubra to accumulate Zn and V. myuros to accumulate Pb in the roots would facilitate a more efficient phytoremediation strategy when used in combination.

Hormone regulation of rhizome development in tall fescue (Festuca arundinacea) associated with proteomic changes controlling respiratory and amino acid metabolism

BACKGROUND AND AIMS

Rhizomes are underground stems with meristematic tissues capable of generating shoots and roots. However, mechanisms controlling rhizome formation and growth are yet to be completely understood. The objectives of this study were to investigate whether rhizome development could be regulated by cytokinins (CKs) and gibberellic acids (GAs), and determine underlying mechanisms of regulation of rhizome formation and growth of tall fescue (Festuca arundinacea) by a CK or GA through proteomic and transcript analysis.

METHODS

A rhizomatous genotype of tall fescue ('BR') plants were treated with 6-benzylaminopurine (BAP, a synthetic cytokinin) or GA3 in hydroponic culture in growth chambers. Furthermore, comparative proteomic analysis of two-dimensional electrophoresis and mass spectrometry were performed to investigate proteins and associated metabolic pathways imparting increased rhizome number by BAP and rhizome elongation by GA3 KEY RESULTS: BAP stimulated rhizome formation while GA3 promoted rhizome elongation. Proteomic analysis identified 76 differentially expressed proteins (DEPs) due to BAP treatment and 37 DEPs due to GA3 treatment. Cytokinin-related genes and cell division-related genes were upregulated in the rhizome node by BAP and gibberellin-related and cell growth-related genes in the rhizome by GA3 CONCLUSIONS: Most of the BAP- or GA-responsive DEPs were involved in respiratory metabolism and amino acid metabolism. Transcription analysis demonstrated that genes involved in hormone metabolism, signalling pathways, cell division and cell-wall loosening were upregulated by BAP or GA3 The CK and GA promoted rhizome formation and growth, respectively, by activating metabolic pathways that supply energy and amino acids to support cell division and expansion during rhizome initiation and elongation in tall fescue.

Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion

Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing ('K-31'), and a dwarf cultivar ('Bonsai') of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of 'K-31' was 63% greater than that of 'Bonsai', which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue.

He-Ne laser preillumination improves the resistance of tall fescue (Festuca arundinacea Schreb.) seedlings to high saline conditions

In this paper, we explored the protective effect and physiochemical mechanism of He-Ne laser preillumination in enhancement of tall fescue seedlings tolerance to high salt stress. The results showed that salt stress greatly reduced plant growth, plant height, biomass, leaf development, ascorbate acid (AsA) and glutathione (GSH) concentration, the enzymatic activities, and gene expression levels of antioxidant enzymes such as catalase (CAT) and glutathione reductase (GR) and enhanced hydrogen peroxide (H2O2) content, superoxide radical (O2 (·-)) generation rates, membrane lipid peroxidation, relative electrolyte leakage, the enzymatic activities, and gene expression levels of superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD), compared with controls. However, He-Ne laser preillumination significantly reversed plant growth retardation, biomass loss, and leaves development decay induced by salt stress. And the values of the physiochemical parameters observed in salt-stressed plants were partially reverted or further increased by He-Ne laser. Salt stress had no obvious effect on the transcriptional activity of phytochromeB, whereas He-Ne laser markedly enhanced its transcriptional level. Preillumination with white fluorescent lamps (W), red light (RL) of the same wavelength, or RL, then far-red light (FRL) had not alleviated the inhibitory effect of salt stress on plant growth and antioxidant enzymes activities, suggesting that the effect of He-Ne laser on improved salt tolerance was most likely attributed to the induction of phytochromeB transcription activities by the laser preillumination, but not RL, FRL or other light sources. In addition, we also utilized sodium nitroprusside (SNP) as NO donor to pre-treat tall fescue seedlings at the same conditions, and further evaluated the differences of physiological effects between He-Ne laser and NO in increasing salt resistance of tall fescue. Taken together, our data illustrated that He-Ne laser preillumination contributed to conferring an increased tolerance to salt stress in tall fescue seedlings due to alleviating oxidative damage through scavenging free radicals and inducing transcriptional activities of some genes involved in plant antioxidant system, and the induction of phytochromeB transcriptional level by He-Ne laser was probably correlated with these processes. Moreover, this positive physiochemical effect seemed more effective with He-Ne laser than NO molecule.

Angelicin as the principal allelochemical in Heracleum sosnowskyi fruit

Distribution patterns of furocoumarins in fruits of the invasive species Heracleum sosnowskyi Manden. (Sosnowskyi's hogweed) during a cold stratification period were investigated. Angelicin, bergapten, methoxalen and imperatorin were mainly localized in the fruit coats and their content varied depending on the fruit source. Cold stratification treatment (90 days, 2-3 degrees C) reduced the content of furocoumarins in the fruit coats by more than two times, compared with those before stratification. The specific activity of the detected furocoumarins and total activity of crude extracts were evaluated using Lactuca sativa, as acceptor plant. Crude extracts obtained from fruit coats and seeds of H. sosnowskyi suppressed 50% of radicle and hypocotyl growth of lettuce seedlings at the concentration range of 1.0-1.7 mg/mL. The inhibitory activity of angelicin was proved to be the highest compared with the other tested furocoumarins, and the inhibitory activity of crude extracts could be explained mainly by the presence of angelicin. Both, monocots (Lolium multiflorum, Phleum pratensis, Festuca pratesis, Lolium perenne) and dicots (Tripholium repens, Trifolium pretense) were found to be sensitive to the exudates of whole H. sosnowskyi fruits. Thus, we assume, that high inhibitory potential of furocoumarins, especially angelicin, at high seed productivity of H. sosnowskyi might have an ecological significance in plant-plant interaction.

Allelopathic Potential of Invasive Plantago virginica on Four Lawn Species

Plantago virginica L. has invaded many lawn ecosystems in the Eastern part of China. The invasion has incurred an economic cost to remove them. In order to prevent the invasion, it is critical to understand the invasive mechanisms of this species. However, few studies have been conducted on the allelopathic mechanisms of its invasion. In this study, we examined allelopathic effects of P. virginica on germination of seeds and growth of seedlings of four widely used lawn species. We found extensive allelopathic potential of P. virginica on other lawn species, which varied with species and developmental stage. While most effects of the extracts of P. virginica were inhibitory, some variables in some species were promoted by the addition of the extracts. The extracts of P. virginica significantly inhibited seed germination of Agrostis matsumurae. While the overall differences in seed germination rate of Poa annua were significant among treatments, difference between control and any of the treatments was not significant. The height of seedlings of A. matsumurae and Cynodon dactylon was significantly lower under the treatments of adding extracts of P. virginica. In contrast, growth of seedlings of Festuca elata and P. annua did not show significant differences among treatments. The root length of A. matsumurae, C. dactylon and P. annua was suppressed by the extracts of P. virginica whereas root length of F. elata was not affected. Aboveground biomass of A. matsumurae and F. elata was significantly higher than control, except for F. elata at the concentration of 50mg/mL, whereas aboveground biomass of C. dactylon and P. annua was reduced at higher concentrations of the extracts. Except for A. matsumurae, root biomass of the other three lawn species declined under the treatments with the extracts of P. virginica. Our results revealed that P. virginica had allelopathic potential on four lawn species and supported the theory of "novel weapons hypothesis". Invasion by P. virginica in lawn can be moderated by selecting those species that are not affected or promotionally affected by it.

Changes in the abundance of sugars and sugar-like compounds in tall fescue (Festuca arundinacea) due to growth in naphthalene-treated sand

The hydrophilic metabolome of tall fescue (Festuca arundinacea) adapted to grow in naphthalene-treated sand (0.8 g kg(-1) sand dw) was analysed using gas chromatography-mass spectrometry, and peaks corresponding to the more abundant compounds were tentatively identified from analysis of their mass spectral features and reference to the NIST Mass Spectral Database. Particular attention was paid to sugars as they are known to play important roles as stress regulators in plants. The results showed that the abundance of sugars was greater in the roots but lesser in the shoots of treated plants when compared to their control counterparts. The results for indole acetic acid (IAA) were notable: IAA was prominently less in the treated roots compared to shoots, and in treated shoots, IAA was particularly subdued compared to untreated shoots consistent with IAA degradation in treated plant tissues. The differences in the molecular phenotype between control and treated plants were expressed in root structural differences. The treated roots were modified to have greater suberisation, enhanced thickening in the endodermis and distortions in the cortical zone as demonstrated through scanning electron and epi-fluorescence microscopy.

Physiological effects of temperature on turfgrass tolerance to amicarbazone

BACKGROUND

Amicarbazone effectively controls annual bluegrass (Poa annua L.) in bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] and tall fescue (Festuca arundinacea Schreb.) with spring applications, but summer applications may excessively injure tall fescue. The objective of this research was to investigate physiological effects of temperature on amicarbazone efficacy, absorption, translocation and metabolism in annual bluegrass, bermudagrass and tall fescue.

RESULTS

At 25/20 °C (day/night), annual bluegrass absorbed 58 and 40% more foliar-applied amicarbazone than bermudagrass and tall fescue, respectively, after 72 h. Foliar absorption increased at 40/35 °C in all species, compared with 25/20 °C, and tall fescue had similar absorption to annual bluegrass at 40/35 °C. At 6 days after treatment, annual bluegrass metabolized 54% of foliar-applied amicarbazone, while bermudagrass and tall fescue metabolized 67 and 64% respectively.

CONCLUSION

Tall fescue is more tolerant to amicarbazone than annual bluegrass at moderate temperatures (≈25/20 °C) owing to less absorption and greater metabolism. However, tall fescue susceptibility to amicarbazone injury at high temperatures (40/35 °C) results from enhanced herbicide absorption compared with lower temperatures (25/20 °C). Bermudagrass is more tolerant to amicarbazone than annual bluegrass and tall fescue owing to less herbicide absorption, regardless of temperature.

Growth responses of two tall fescue cultivars to Pb stress and their metal accumulation characteristics

Tall fescue (Festuca arundinacea), a widely planted cool-season turfgrass and forage, is tolerant to heavy metals. However, previous investigation demonstrated that different accessions varied in Pb tolerance. In present study, hydroponic system was used to study the effects of Pb on two tall fescue cultivars, Pb tolerant 'Silverado' and Pb sensitive 'AST7001', respectively. The results indicated that Pb concentration was 14 times lower in shoots of 'Silverado' (1.34 mg g(-1) dry weight) versus 'AST7001' (19.92 mg g(-1) dry weight), although it was higher in roots of 'Silverado' (68.28 mg g(-1) dry weight) versus 'AST7001' (48.7 mg g(-1) dry weight), when subjected to 1,000 mg L(-1) Pb. In both cultivars, Pb caused an induction in malondialdehyde (MDA) content, to a less increase in 'Silerado' than 'AST7001'. Pb treatment decreased significantly soluble protein content in 'AST7001'. By contrast, soluble protein content was increased progressively, and the ratio of variable to maximal chlorophyll fluorescence was not affected in 'Silverado'. Pb treated tall fescue leaves had a greater level of superoxide dismutase (SOD) and guaiacol peroxidase (POD) activity in both cultivars, however, increase was sharp in 'Silverado' plants. The results of Q-PCR analysis for genes encoding antioxidant enzyme were in accordance with that of enzyme activities. The higher Pb tolerance of 'Silverado' might be attributed to lower shoot Pb concentration and MDA content. Meantime, the amount of soluble protein, activity of SOD and POD, as well as the level of up regulation of Cyt Cu/ZnSOD was all higher in 'Silverado' than in 'AST7001'.

Scanning electron microscopic investigations of root structural modifications arising from growth in crude oil-contaminated sand

The choice of plant for phytoremediation success requires knowledge of how plants respond to contaminant exposure, especially their roots which are instrumental in supporting rhizosphere activity. In this study, we investigated the responses of plants with different architectures represented by beetroot (Beta vulgaris), a eudicot with a central taproot and many narrower lateral roots, and tall fescue (Festuca arundinacea), a monocot possessing a mass of threadlike fibrous roots to grow in crude oil-treated sand. In this paper, scanning electron microscopy was used to investigate modifications to plant root structure caused by growth in crude oil-contaminated sand. Root structural disorders were evident and included enhanced thickening in the endodermis, increased width of the root cortical zone and smaller diameter of xylem vessels. Inhibition in the rate of root elongation correlated with the increase in cell wall thickening and was dramatically pronounced in beetroot compared to the roots of treated fescue. The latter possessed significantly fewer (p < 0.001) and significantly shorter (p < 0.001) root hairs compared to control plants. Possibly, root hairs that absorb the hydrophobic contaminants may prevent contaminant absorption into the main root and concomitant axile root thickening by being sloughed off from roots. Tall fescue exhibited greater root morphological adaptability to growth in crude oil-treated sand than beetroot and, thus, a potential for long-term phytoremediation.

Cloning and characterization of a Phragmites australis phytochelatin synthase (PaPCS) and achieving Cd tolerance in tall fescue

The production of phytochelatins (PCs) provides an important means for plants to achieve tolerance to cadmium (Cd) toxicity. A reed gene encoding PC synthase (PaPCS) was isolated and its function tested through its heterologous expression in a strain of yeast sensitive to Cd. Subsequently, the Cd sensitive and high biomass accumulating species tall fescue was transformed either with PaPCS or PaGCS (a glutamyl cysteine synthetase gene of reed) on their own (single transformants), or with both genes together in the same transgene cassette (double transformant). The single and double transformants showed greater Cd tolerance and accumulated more Cd and PC than wild type plants, and their Cd leaf/root ratio content was higher. The ranking in terms of Cd and PC content for the various transgenic lines was double transformants>PaGCS single transformants>PaPCS single transformants>wild type. Thus PaGCS appears to exert a greater influence than PaPCS over PC synthesis and Cd tolerance/accumulation. The double transformant has interesting potential for phytoremediation.

Ion uptake in tall fescue as affected by carbonate, chloride, and sulfate salinity

Turfgrass nutrient uptake may be differentially affected by different salts. The objective of this study was to compare nutrient uptake in tall fescue (Festuca arundinacea Schreb.) as affected by carbonate, chloride, and sulfate under iso-osmotic, iso-Na⁺ strength conditions. ‘Tar Heel II’ and ‘Wolfpack’ cultivars were subjected to NaCl, Na₂CO₃, Na₂SO₄, CaCl₂, NaCl+ CaCl₂, Na₂CO₃+ CaCl₂, and Na₂SO₄+ CaCl₂, in the range of 0 to 225 mM. There was no cultivar difference regarding K, Na, Mg, and Mn content in shoots. ‘Tar Heel II’ had higher shoot Ca content than ‘Wolfpack’, which were 6.9 and 5.7 g kg⁻¹, respectively. In general, K⁺/Na⁺ ratio decreased with increasing salt concentrations, which reached <1 at about 87.5 mM in Na₂CO₃ treatment. All salt treatments decreased Mg content in shoot tissues, especially in Na₂CO₃ and treatments containing CaCl₂. Both Ca and Mg content in shoot were higher in the NaCl treatment than the Na₂SO₄ and Na₂CO₃ treatments. All salt treatments except Na₂CO₃ had higher Mn content in shoots compared to the control. In conclusion, nutrient uptake was differently affected by carbonate, chloride, and sulfate which are different in pH, electrical conductivity (EC), and osmotic potential at the same concentration. Adding Ca to the sodium salts increased Ca content and balanced K⁺/Na⁺ in shoots, but did not increase Mg content, which was below sufficient level. Maintaining Mg content in shoots under salinity stress was recommended. The physiological impact of elevated Mn content in shoot under salinity stress requires further study.

Potential for phytoextraction of copper by Sinapis alba and Festuca rubra cv. Merlin grown hydroponically and in vineyard soils

The extensive use of copper-bearing fungicides in vineyards is responsible for the accumulation of copper (Cu) in soils. Grass species able to accumulate Cu could be cultivated in the vineyard inter-rows for copper phytoextraction. In this study, the capacity of Festuca rubra cv Merlin and Sinapis alba to tolerate and accumulate copper (Cu) was first investigated in a hydroponic system without the interference of soil chemical-physical properties. After the amendment of Cu (5 or 10 mg Cu l-(1)) to nutrient solution, shoot Cu concentration in F. rubra increased up to 108.63 mg Cu kg(-1) DW, more than three times higher than in S. alba (31.56 mg Cu kg(-1) DW). The relationship between Cu concentration in plants and external Cu was dose-dependent and species specific. Results obtained from the hydroponic experiment were confirmed by growing plants in pots containing soil collected from six Italian vineyards. The content of soil organic matter was crucial to enhance Cu tolerance and accumulation in the shoot tissues of both plant species. Although S. alba produced more biomass than F. rubra in most soils, F. rubra accumulated significantly more Cu (up to threefold to fourfold) in the shoots. Given these results, we recommended that F. rubra cv Merlin could be cultivated in the vineyard rows to reduce excess Cu in vineyard soils.

Interaction of heavy metals and pyrene on their fates in soil and tall fescue (Festuca arundinacea)

90-Day growth chamber experiments were performed to investigate the interactive effect of pyrene and heavy metals (Cu, Cd, and Pb) on the growth of tall fescue and its uptake, accumulation, and dissipation of heavy metals and pyrene. Results show that plant growth and phytomass production were impacted by the interaction of heavy metals and pyrene. They were significantly decreased with heavy metal additions (100-2000 mg/kg), but they were only slightly declined with pyrene spiked up to 100 mg/kg. The addition of a moderate dosage of pyrene (100 mg/kg) lessened heavy metal toxicity to plants, resulting in enhanced plant growth and increased metal accumulation in plant tissues, thus improving heavy metal removal by plants. In contrast, heavy metals always reduced both plant growth and pyrene dissipation in soils. The chemical forms of Cu, Cd, and Pb in plant organs varied with metal species and pyrene addition. The dissipation and mineralization of pyrene tended to decline in both planted soil and unplanted soils with the presence of heavy metals, whereas they were enhanced with planting. The results demonstrate the complex interactive effects of organic pollutants and heavy metals on phytoremediation in soils. It can be concluded that, to a certain extent, tall fescue may be useful for phytoremediation of pyrene-heavy metal-contaminated sites. Further work is needed to enhance methods for phytoremediation of heavy metal-organics co-contaminated soil.

Metabolite analysis of the effects of elevated CO2 and nitrogen fertilization on the association between tall fescue (Schedonorus arundinaceus) and its fungal symbiont Neotyphodium coenophialum

Atmospheric CO2 is expected to increase to between 550 ppm and 1000 ppm in the next century. CO2-induced changes in plant physiology can have ecosystem-wide implications and may alter plant-plant, plant-herbivore and plant-symbiont interactions. We examined the effects of three concentrations of CO2 (390, 800 and 1000 ppm) and two concentrations of nitrogen fertilizer (0.004 g N/week versus 0.2 g N/week) on the physiological response of Neotyphodium fungal endophyte-infected and uninfected tall fescue plants. We used quantitative PCR to estimate the concentration of endophyte under altered CO2 and N conditions. We found that elevated CO2 increased the concentration of water-soluble carbohydrates and decreased the concentration of plant total amino acids in plants. Fungal-derived alkaloids decreased in response to elevated CO2 and increased in response to nitrogen fertilization. Endophyte concentration (expressed as the number of copies of an endophyte-specific gene per total genomic DNA) increased under elevated CO2 and nitrogen fertilization. The correlation between endophyte concentration and alkaloid production observed at ambient conditions was not observed under elevated CO2. These results suggest that nutrient exchange dynamics important for maintaining the symbiotic relationship between fungal endophytes and their grass hosts may be altered by changes in environmental variables such as CO2 and nitrogen fertilization.

The effect of glyphosate on the growth and competitive effect of perennial grass species in semi-natural grasslands

Biodiversity within European semi-natural biotopes in agro-ecosystem is declining, and herbicide drift from neighbouring fields is considered as an important factor for the decline. The aim of the present study was to investigate whether the growth and competitive interactions in a model system of two perennial grass species, Festuca ovina and Agrostis capillaris, are affected by sub-lethal doses of glyphosate in field margins. In a glasshouse experiment with ample nitrogen, the interspecific competitive interactions were found to be significantly affected by glyphosate; the competitive effect of F. ovina on A. capillaris increased and the competitive effect of A. capillaris on F. ovina decreased with increasing doses of glyphosate. Furthermore, the importance of interspecific competition increased with the glyphosate dose. The results of the study of competitive interactions are in agreement with the observed plant community dynamics at the field site where F. ovina was found to be more dominant in plots treated with a relatively high dose of glyphosate. Importantly, the effects of glyphosate on the plant community dynamics critically depended on the effect of glyphosate on the plant competitive interactions. The study concludes that the current practice in the environmental risk assessment of non-target effects of herbicides, where single species are tested in the greenhouse, may be inadequate for assessing the effect of herbicides in semi-natural plant communities. The presented methods can be used for assessing the importance of competitive interactions for the sensitivity of non-target plants to herbicides in risk assessment.

Alleviation of heat damage to photosystem II by nitric oxide in tall fescue

Nitric oxide (NO) has been found to mediate plant responses to heat stress. The objective of this study was to investigate the protective role of NO in the recovery process of photosystem II (PSII) in tall fescue (Festuca arundinacea) against heat stress. Treatment of tall fescue leaves with NO donor sodium nitroprusside significantly improved the overall behavior of PSII probed by the chlorophyll a fluorescence transients, while the inhibition of NO accumulation by 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO, a NO scavenger) plus N (G)-nitro-L-arginine-methyl ester (L-NAME, NO synthase inhibitor) dramatically disrupted the operation of PSII. Specifically, under heat stress, the exogenous NO reduced the initial fluorescence (F 0), increased the maximal quantum yield (F V/F M), and disappeared the K-step of 0.3 ms. By the analysis of the JIP-test, the exogenous NO improved the quantum yield of the electron transport flux from Q A to Q B (ET0/ABS), and decreased the trapped excitation flux per reaction center (RC) (TR0/RC), electron transport flux per RC (ET0/RC), and electron flux reducing end electron acceptors per RC (RE0/RC). In addition, the exogenous NO reduced the content of H2O2, O 2 (•-) , and malondialdehyde and electrolyte leakage of tall fescue leaves. These data suggest that exogenous NO could protect plants, increase the amount of activated RC and improve the electron transport from oxygen evolving complex to D1 protein. Moreover, quantitative RT-PCR revealed that, in the presence of hydrogen peroxide, NO induced the gene expression of psbA, psbB, and psbC, which encode proteins belonging to subunits of PSII core reaction center (Psb) complex. These findings indicate that, as an important strategy to protect plants against heat stress, NO could improve the recovery process of PSII by the up regulation of the transcriptions of genes encoding PSII core proteins.

Long-term stability and risk assessment of lead in mill waste treated by soluble phosphate

In an effort to address public concerns of the long-term stability and ecological risk reduction of phosphate (P)-stabilized lead (Pb) in mine wastes, mill tailings located at the Jasper County Superfund Site of southwest Missouri, containing ~4000 mg Pb kg(-1), were treated in situ by phosphoric acid at three rates: 0; 7.5; and 10.0 g P kg(-1) soil. Field experiment consisted of 2- by 4-m plots arranged in a randomized complete block design with four replicates of each P level. Soil and plant samples were collected at a 3-month interval during five to six (5-6) years post treatments and analyzed for Pb bioaccessibility and leachability, microbial toxicity, Pb chemical fraction, and elemental composition of Pb solids, and Pb concentration in plant tissue. Results indicated that the P treatments significantly reduced bioaccessible and leachable Pb in the mill waste, and the reductions were maintained during the sampling period. Lead concentration in plant tissue was positively related to the Pb bioaccessibility. There was no significant toxicological effect of the treatments on soil microbial community. The treatment using 10 g P kg(-1) appeared to be most effective for overall risk reduction. The Pb stabilization and risk reduction by the P treatments were accomplished by the induced transformation of labile Pb species to relatively insoluble forms, probably pyromorphite-like minerals. This study illustrated that in situ Pb stabilization by soluble phosphate would be long-term and ecologically-safe, which could safeguard human health and ecosystem from Pb contamination in mining areas.

Utility of bioassays (lettuce, red clover, red fescue, Microtox, MetSTICK, Hyalella, bait lamina) in ecological risk screening of acid metal (Zn) contaminated soil

The objective of this study was to assess selected bioassays and ecological screening tools for their suitability in a weight of evidence risk screening process of acidic metal contaminated soil. Intact soil cores were used for the tests, which minimizes changes in pH and metal bioavailability that may result from homogenization and drying of the soil. Soil cores were spiked with ZnCl(2) or CaCl(2). Leachate collected from the soil cores was used to account for the exposure pathways through pore water and groundwater. Tests assessed included MetSTICK in soil cores and Microtox in soil leachate, lettuce (Lactuca sativa), red fescue (Festuca rubra) and red clover (Trifolium pratense) in the soil cores and lettuce and red clover in soil leachate, Hyallella azteca in soil leachate, and an ecological soil function test using Bait Lamina in soil cores. Microtox, H. azteca, lettuce and red fescue showed higher sensitivity to low pH than to Zn concentrations and are therefore not recommended as tests on intact acidic soil cores and soil leachate. The Bait Lamina test appeared sensitive to pH levels below 3.7 but should be investigated further as a screening tool in less acidic soils. Among the bioassays, the MetSTICK and the T. pratense bioassays in soil cores were the most sensitive to Zn, with the lowest nominal NOEC of 200 and 400mg Zn/kg d.w., respectively. These bioassays were also tolerant of low pH, which make them suitable for assessing hazards of metal contaminated acid soils.

Improvement of paper mulberry tolerance to abiotic stresses by ectopic expression of tall fescue FaDREB1

Dehydration-responsive element binding/C-repeat-binding factors (DREB/CBF) control the activity of multiple stress response genes and therefore represent attractive targets for genetic improvement of abiotic stress tolerance. Paper mulberry (Broussonetia papyrifera L. Vent) is well known for its bark fibers and high levels of chalcone and flavonoid derivatives. Transgenic paper mulberry plants expressing a tall fescue (Festuca arundinacea Schreb.) FaDREB1 gene under the control of CaMV 35S were produced to examine the potential utility of FaDREB1 to increase the tolerance of paper mulberry plants to abiotic stress. The overexpressing FaDREB1 plants showed higher salt and drought tolerance than the wild-type plants (WT). After 13 days of withholding water, or 15 days in the presence of 250 mM NaCl, all the WT plants died, while the over-expressing FaDREB1 plants survived. The FaDREB1 plants had higher leaf water and leaf chlorophyll contents, accumulated more proline and soluble sugars, and had less ion leakage (which reflects membrane damage) than the WT plants had under high salt- and water-deficient conditions. The 35S promoter-driven expression of FaDREB1 did not cause growth retardation under normal growth conditions. Therefore, improved tolerance to multiple environmental stresses in paper mulberry might be achieved via genetic engineering through the ectopic expression of an FaDREB1 gene.

Ectopic expression of FaDREB2 enhances osmotic tolerance in paper mulberry

Dehydration-responsive element binding (DREB) proteins are a subfamily of AP2/ERF transcription factors that have been shown to improve tolerance to osmotic stresses in plants. To improve the osmotic stress tolerance of paper mulberry (Broussonetia papyrifera L. Vent), an economically important tree, we transformed it with a plasmid carrying tall fescue (Festuca arundinacea Schreb) FaDREB2 under the control of CaMV 35S. The ectopic expression of FaDREB2 did not cause growth retardation, and the paper mulberry seedlings expressing FaDREB2 showed higher salt and drought tolerance than wild-type plants (WT). After 13 d of withholding water, or 15 d in the presence of 250 mM NaCl, all the WT plants died, while the plants expressing FaDREB2 survived. The FaDREB2 transgenic plants had higher leaf water and chlorophyll contents, accumulated more proline and soluble sugars, and had less membrane damage than the WT plants under high salt and water-deficient conditions. Taken together, the results indicate the feasibility of improving tolerance to multiple environmental stresses in paper mulberry seedlings via genetic engineering, by introducing FaDREB2, which promotes the increased accumulation of osmolytes (soluble sugars and proline), to counter osmotic stresses caused by abiotic factors.

Phytoremediation and removal mechanisms in Bouteloua curtipendula growing in sterile hydrocarbon spiked cultures

Tolerance index and phytoremediation factors of side oats grama (Bouteloua curtipendula) with recalcitrant polycyclic aromatic hydrocarbons (PAH) phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) and the resulting impact on phenotypic response, were evaluated in sterile conditions with whole plant growing in test-tube cultures with MS medium with PAH and compared with Tall fescue (Festuca arundinacea), control for this study. PAH mixture of PHE, PYR and BaP (1:1:1 w/w/w) blended with Maya crude oil (1:1 w/w), final concentration of 1500 mg kg(-1) was used. After 40 days, BaP removal, in the presence of Maya crude was superior compared with PHE and PYR removal Although the presence of PAH negatively affects the phenotypic response of the plants; sterile conditions experiments were helpful to evaluate phytoremediation factors to elucidate some important questions regarding phytoremediation mechanisms; in this study, B. curtipendula was able to phytostabilizate BaP associated to a significant hydrocarbon removal (57.4%) with high root accumulation but attenuated transport to stems, here reported as translocation factor. To our knowledge, this is the first time that quantifiable phytoremediation factors were used to evaluate the tolerance and removal capacity of a native semi-arid climate plant which is probably able to phytoremediate hydrocarbon contaminated soils.

Endophytic fungus improves growth and metal uptake of Lolium arundinaceum Darbyshire ex. Schreb

The effect of endophyte infection on plant growth, cadmium (Cd) uptake, and Cd translocation was investigated using tall fescue (Lolium arundinaceum) grown in greenhouses in contaminated solution. Endophyte infection significantly increased tiller number and biomass of the host grass under both control and Cd-stress conditions. Endophyte infection not only enhanced Cd accumulation in tall fescue, but also improved Cd transport from the root to the shoot. Under 20 mg L(-1) Cd stress, the phytoextraction efficiency of endophyte-infected (EI) tall fescue was 2.41-fold higher than endophyte-free plants. Although the total Cd accumulation in EI tall fescue was insufficient for practical phytoextraction applications, the observed high biomass production and tolerance of stress from abiotic factors including heavy metals, gives endophyte/plant associations the potential to be a model for endophyte-assisted phytoremediation of metal-polluted soils.

Glutathione peroxidases in Lolium multiflorum and Festuca arundinacea: Activity, susceptibility to herbicides and characteristics

To evidence a possible mechanism of defense toward oxidative stress induced by herbicides in plants, an investigation was carried on the activity of glutathione peroxidase (GPX) in Italian ryegrass (Lolium multiflorum) and in Festuca (Festuca arundinacea) in response to atrazine (6-chloro-N-ethyl-N'-isopropyl-1,3,5-triazine-2,4-diamine) and fluorodifen (4-nitrophenyl α,α,α-trifluoro-2-nitro-p-tolyl ether). In general, the herbicide treatments significantly induced GPX activity in the shoots of Italian ryegrass, whereas inhibited it in Festuca. These opposite behaviors are examined, taking into account the accumulation and persistence of the two herbicides in the plants, and they are discussed in terms of GPX counteraction to oxidative stress in the first case, and of a lower detoxification rate unable to prevent a deleterious effect on the GPX activity in the second case. Further information on the properties of Italian ryegrass and Festuca GPX were achieved by purification and isolation of the enzymes, performed by protein liquid chromatography and by electrophoretic analyses. GPX of both the plants were found to be heterodimer with multiple function in showing also glutathione S-transferase (GST) activity.

Catechin is a phytototoxin and a pro-oxidant secreted from the roots of Centaurea stoebe

When applied to the roots of Arabidopsis thaliana, the phytotoxin (±)-catechin triggers a wave of reactive oxygen species (ROS), leading to a cascade of genome-wide changes in gene expression and, ultimately, death of the root system. Biochemical links describing the root secreted phytotoxin, (±)-catechin, represent one of most well studied systems to describe biochemically based negative plant-plant interactions, but of late have also sparked controversies on phytotoxicity and pro-oxidant behavior of (±)-catechin. The studies originating from two labs ( 1- 3) maintained that (±)-catechin is not at all phytotoxic but has strong antioxidant activity. The step-wise experiments performed and the highly correlative results reported in the present study clearly indicate that (±)-catechin indeed is phytotoxic against A. thaliana and Festuca idahoensis. Our results show that catechin dissolved in both organic and aqueous phase inflict phytotoxic activity against both A. thaliana and F. idahoensis. We show that the deviation in results highlighted by the two labs ( 1- 3) could be due to different media conditions and a group effect in catechin treated seedlings. We also determined the presence of catechin in the growth medium of C. stoebe to support the previous studies. One of the largest functional categories observed for catechin-responsive genes corresponded to gene families known to participate in cell death and oxidative stress. Our results showed that (±)-catechin treatment to A. thaliana plants resulted in activation of signature cell death genes such as accelerated cell death (acd2) and constitutively activated cell death 1 (cad1). Further, we confirmed our earlier observation of (±)-catechin induced ROS mediated phytotoxicity in A. thaliana. We also provide evidence that (±)-catechin induced ROS could be aggravated in the presence of divalent transition metals. These observations have significant impact on our understanding regarding catechin phytotoxicity and pro-oxidant activity. Our data also illustrates that precise conditions are needed to evaluate the effect of catechin phytotoxicity.

Effect of endophytic fungi on cadmium tolerance and bioaccumulation by Festuca arundinacea and Festuca pratensis

Endophytic fungi are a group of fungi that live asymptomatically inside plant tissue. These fungi may increase host plant tolerance to biotic and abiotic stresses. The effect of Neotyphodium endophytes in two grass species (Festuca arundinacea and Festuca pratensis) on cadmium (Cd) tolerance, accumulation and translocation has been our main objective. The plants were grown in a hydroponic system under different Cd concentrations (0, 5, 10, and 20 mg L(-1)) for 6 weeks. They were also grown in soil spiked with different concentrations of Cd (0, 10, 20, and 40 mg kg(-1)) for 2 months. The results from all Cd treatments showed higher biomass production (12-24%) and higher potential to accumulate Cd in roots (6-16%) and shoots (6-20%) of endophyte-infected plants than endophyte-free plants. Cadmium accumulation by plants indicated that the grasses were capable of Cd hyperaccumulation, a property that was augmented after endophyte infection. Maximum photochemical efficiency of photosystem II (Fv/Fm) revealed that Cd stress was significantly reduced in endophyte-infected plants compared to non-infected ones.

Selecting tolerant grass seedlings and analyzing the possibility for using aged refuse as sward soil

In order to test the possibility for recycling use of aged refuse as sward soil, the study determined the responses of Lolium perenne L. (perennial ryegrass), Festuca arundinacea (tall fescue), and Poa annua (annual bluegrass) to its leaching. The growth of three seedlings was significantly inhibited after treatment, especially for longer treatment duration and higher concentration leaching; however, with the better growth and chlorophyll content for shorter time and lower concentration, tall fescue was more tolerant to the stress. Afterwards, several physiological responses of tall fescue were determined. For shorter treatment duration, antioxidant enzyme activities remained unchanged, and no obvious oxidative damage was observed. Prolonging exposure time, lipid peroxidation and protein oxidation occurred after treatment of higher concentration leaching, accompanying by changes of antioxidant status. It implicates that it is possible for using aged refuse as sward soil, and the critical point focused on selecting tolerant grass and controlling exposure condition.

Genome-wide profiling and analysis of Festuca arundinacea miRNAs and transcriptomes in response to foliar glyphosate application

Glyphosate is a broad spectrum herbicide which has been widely used for non-selective weed control in turfgrass management. Festuca arundinacea cv. Falcon was shown to be one of the tolerant turfgrass species in response to varying levels of glyphosate [5% (1.58 mM), 20% (6.32 mM)] recommended for weed control. However, there is a lack of knowledge on the mRNA expression patterns and miRNA, critical regulators of gene expression, in response to varying levels of glyphosate treatments. Here, we investigate the transcriptome and miRNA-guided post-transcriptional networks using plant miRNA microarray and Affymetrix GeneChip Wheat Genome Array platforms. Transcriptome analysis revealed 93 up-regulated and 78 down-regulated genes, whereas a smaller number showed inverse differential expressions. miRNA chip analysis indicated a number of (34 out of the 853) plant miRNAs were differentially regulated in response to glyphosate treatments. Target transcripts of differentially regulated miRNAs were predicted and nine of them were quantified by quantitative real-time PCR (qRT-PCR). Target transcripts of miRNAs validate the expression level change of miRNAs detected by miRNA microarray analysis. Down-regulation of miRNAs upon 5 and 20% glyphosate applications led to the up-regulation of their target observed by qRT-PCR or vice versa. Quantification of F. arundinacea miRNA, homologous of osa-miR1436, revealed the agreement between the Affymetrix and miRNA microarray analyses. In addition to miRNA microarray experiment, 25 conserved F. arundinacea miRNAs were identified through homology-based approach and their secondary structures were predicted. The results presented serve as analyses of genome-wide expression profiling of miRNAs and target mRNAs in response to foliar glyphosate treatment in grass species.

Festuca arundinacea, glutathione S-transferase and herbicide safeners: a preliminary case study to reduce herbicidal pollution

The expression of glutathione S-transferase (GST) activity in Festuca arundinacea was investigated in response to the following herbicide safeners: benoxacor, cloquintocet-mexyl, fenchlorazol-ethyl, fenclorim, fluxofenim and oxabetrinil. All the above compounds enhanced the GST activity tested towards the "model" substrate 1-chloro-2,4-dinitrobenzene (CDNB). Assays of GST activity towards the herbicides terbuthylazine (N(2)-tert-butyl-6-chloro-N(4)-ethyl-1,3,5-triazine-2,4-diamine) and butachlor (N-butoxymethyl-2-chloro-2',6'-diethylacetanilide) as substrates also showed the ability of the safeners to enhance the enzyme activity towards both these herbicides, with the exception of cloquintocet-mexyl for the enzyme activity towards butachlor. As a consequence of the above effects at a macro-scale level, decreased herbicide accumulation and persistence were ascertained in response to the addition of the safener benoxacor to both terbuthylazine and butachlor treatments. These results are discussed in terms of capacity of benoxacor to induce herbicide detoxification in Festuca arundinacea with a view to utilizing them in reducing herbicide pollution.

Comparison of sensitivity of grasses (Lolium perenne L. and Festuca rubra L.) and lettuce (Lactuca sativa L.) exposed to water contaminated with microcystins

The effects of aqueous extracts from Microcysts aeruginosa strains (both microcystin-producers and non-microcystin producers) on germination and root growth were investigated for three economically important plant species: Festuca rubra L., Lolium perenne L., and Lactuca sativa L. There was a clear inhibition of root growth for L. sativa exposed to strains containing microcystins (5.9-56.4 microg L(-1)). The strain that produced the most pronounced effects contained the lowest concentration of microcystin suggesting that other cellular compounds may also affect growth.

Transcript profiling of the salt-tolerant Festuca rubra ssp. litoralis reveals a regulatory network controlling salt acclimatization

We report an analysis of salt-stress responses in the monocotyledonous halophyte Festuca rubra ssp. litoralis. Salt-dependent expression of transcripts encoding a PIP2;1 aquaporin, V-ATPase subunit B, and the Na+/H+ antiporter NHX was characterized. Transcription of FrPIP2;1, FrVHA-B, and FrNHX1 was induced in root tissue of F. rubra ssp. litoralis by salt treatment, and during salt-stress F. rubra ssp. litoralis accumulated sodium in leaves and roots. Cell specificity of FrPIP2;1, FrVHA-B, and FrNHX1 transcription was analyzed by in situ PCR in roots of F. rubra ssp. litoralis. Expression of the genes was localized to the root epidermis, cortex cells, endodermis, and the vascular tissue. In plants treated with 500 mM NaCl, transcripts were repressed in the epidermis and the outer cortex cells, whereas endodermis and vasculature showed strong signals. These data demonstrate that transcriptional regulation of the aquaporin PIP2;1, V-ATPase, and the Na+/H+ antiporter NHX is correlated with salt tolerance in F. rubra ssp. litoralis and suggests coordinated control of ion homeostasis and water status at high salinity in plants. Salt-induced transcript accumulation in F. rubra ssp. litoralis was further monitored by cDNA-arrays with expressed sequence tags derived from a cDNA subtraction library. The salt-regulated transcripts included those involved in the control of gene expression and signal transduction elements such as a serine/threonine protein kinase, an SNF1-related protein kinase, and a WRKY-type transcription factor. Other ESTs with salt-dependent regulation included transcripts encoding proteins that function in metabolism, general stress responses, and defense and transport proteins.