Bio-pump cadmium phytoextraction efficiency promoted by phytohormones in Festuca arundinacea.

The leaves of Festuca arundinacea can excrete cadmium (Cd) out onto the leaf surface, leading to a bio-pump phytoremediation strategy based on "root uptake-root-to-leaf translocation-leaf excretion". However, the bio-bump efficiency of soil Cd is a limiting factor for the implementation of this novel technology. Bio-bump remediation involves the bioprocess of plant root uptake from soil, root-to-leaf translocation, and leaf hydathode excretion. Here we show the significant effects of phytohormones in regulating the bio-pump phytoextraction efficiency. The results showed that salicylic acid and ethylene enhanced the whole process of Cd root uptake, root-to-leaf translocation, and leaf excretion, promoting the bio-pump phytoextraction efficiency by 63.6% and 73.8%, respectively. Gibberellin also greatly promoted Cd translocation, leaf excretion, and phytoextraction, but did not significantly impact Cd root uptake. Our results indicate that salicylic acid and ethylene could be recommended to promote bio-pump phytoextraction efficiency in F. arundinacea. Gibberellin might be used for a short-term promotion of the leaf Cd excretion.

Green Technology as a Way of Cleaning the Environment from Petroleum Substances in South-Eastern Poland.

BACKGROUND: In phytoextraction methods, the problem is the obtained contaminated plant biomass, the selection of the appropriate species, resistant to the type and degree of contamination, as well as the long time needed to completely clean the soil. GOAL: when selecting the appropriate method of remediation of soils contaminated with polycyclic aromatic hydrocarbons, not only the effectiveness of the method should be considered, but also the degree of contamination, the location of the site and its current and planned use. METHODS: Descriptive, laboratory and comparative methods were used. RESULTS: Soil contamination with polycyclic aromatic hydrocarbons (PAHs), which can cause mutations and cancer, is of particular concern as it affects not only human health but also vegetation growth and the biological environment. A fast, nature-friendly and cost-effective method is required to remove and minimize the hazardous effects of crude oil. CONCLUSIONS: Green technology is particularly beneficial, especially the phytoextraction technique, in which plants clean the soil of excess petroleum products, prevent its further movement from the site of contamination and prevent erosion of reclaimed soil. Species such as: Trifolium repens, Trifolium pratense, Lotus corniculatus, Agrostis stolonifera, Festuca rubra subsp. trichophylla, Arrhenatherum elatius performed their tasks very well, therefore they can be recommended for use as a factor counteracting environmental degradation.

5-Aminolevulinic acid promotes low-light tolerance by regulating chloroplast ultrastructure, photosynthesis, and antioxidant capacity in tall fescue.

The vital signaling molecule 5-Aminolevulinic acid (ALA) plays critical roles in signal transduction and biological modulation under abiotic stresses. In this study, we explored the effects of exogenous ALA on low-light (LL) stress-induced photosynthesis and antioxidant system damage in tall fescue (Festuca arundinacea Schreb.) seedlings. LL stress decreased morphological index values and chlorophyll contents, while also reduced net photosynthetic rate (Pn) and the maximum quantum yield of photosystem II photochemistry (Fv/Fm). Notably, these restrictions were substantially alleviated by exogenous ALA. Moreover, the contents of chlorophyll and its synthetic precursors were significantly increased after ALA treatment. Meanwhile, ALA observably enhanced expression level of FaCHLG, FaHEMA, FaPOR, and FaCAO, which encode the chlorophyll precursors biosynthesis enzymes. Exogenous ALA repaired the damage to the chloroplast ultrastructure caused by LL stress and promoted the formation of ordered thylakoids and grana lamella. ALA also improved Rubisco activity and expression level of the photosynthetic enzyme genes FaRuBP, FaPRK, and FaGADPH. Additionally, application of exogenous ALA decreased relative electrolytic leakage and the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide radicals (O2∙-), and increased the gene expression levels and activity of antioxidant enzymes. The ratios of ascorbic acid (AsA) to dehydroascorbic acid (DHA) and reduced glutathione (GSH) to oxidized glutathione (GSSG) were also increased significantly by application of ALA. Furthermore, all responses could be reversed by treatment with levulinic acid (LA). Thus, these results indicated that ALA protects tall fescue from LL stress through scavenging ROS, improving photosynthetic enzyme activity levels, increasing photosynthetic pigments contents, repairing chloroplast damage, and enhancing the photosynthesis rate.

Effect of Sodium Selenite on the Metabolite Profile of Epichloë sp. Mycelia from Festuca sinensis in Solid Culture.

Selenium (Se) is an essential micronutrient with many beneficial effects for humans and other living organisms. Numerous microorganisms in culture systems enrich and convert inorganic selenium to organic selenium. In this study, Epichloë sp. from Festuca sinensis was exposed to increasing Na2SeO3 concentrations (0, 0.1, 0.2, 0.3, and 0.4 mmol/L) in Petri dishes with potato dextrose agar (PDA) for 8 weeks. Epichloë sp. mycelia were immediately collected after mycelial diameters were measured at 4, 5, 6, 7, and 8 weeks of cultivation, respectively. Gas chromatography-mass spectrometer (GC-MS) analysis was performed on different groups of Epichloë sp. mycelia. Different changes were observed as Epichloë sp. was exposed to different selenite conditions and cultivation time. The colony diameter of Epichloë sp. decreased in response to increased selenite concentrations, whereas the inhibitory effects diminished over time. Seventy-two of the 203 identified metabolites did not differ significantly across selenite treatments within the same time point, while 82 compounds did not differ significantly between multiple time points of the same Se concentration. However, the relative levels of 122 metabolites increased the most under selenite conditions. Specifically, between the 4th and 8th weeks, there were increases in 2-keto-isovaleric acid, uridine, and maltose in selenite treatments compared to controls. Selenium increased glutathione levels and exhibited antioxidant properties in weeks 4, 5, and 7. Additionally, we observed that different doses of selenite could promote the production of carbohydrates such as isomaltose, cellobiose, and sucrose; fatty acids such as palmitoleic acid, palmitic acid, and stearic acid; and amino acids such as lysine and tyrosine in Epichloë sp. mycelia. Therefore, Epichloë sp. exposed to selenite stress may benefit from increased levels of some metabolite compounds.

Comparative transcriptome combined with metabolome analyses revealed key factors involved in nitric oxide (NO)-regulated cadmium stress adaptation in tall fescue.

BACKGROUND: It has been reported that nitric oxide (NO) could ameliorate cadmium (Cd) toxicity in tall fescue; however, the underlying mechanisms of NO mediated Cd detoxification are largely unknown. In this study, we investigated the possible molecular mechanisms of Cd detoxification process by comparative transcriptomic and metabolomic approaches. RESULTS: The application of Sodium nitroprusside (SNP) as NO donor decreased the Cd content of tall fescue by 11% under Cd stress (T1 treatment), but the Cd content was increased by 24% when treated with Carboxy-PTIO (c-PTIO) together with Nitro-L-arginine methyl ester (L-NAME) (T2 treatment). RNA-seq analysis revealed that 904 (414 up- and 490 down-regulated) and 118 (74 up- and 44 down-regulated) DEGs were identified in the T1 vs Cd (only Cd treatment) and T2 vs Cd comparisons, respectively. Moreover, metabolite profile analysis showed that 99 (65 up- and 34-down- regulated) and 131 (45 up- and 86 down-regulated) metabolites were altered in the T1 vs Cd and T2 vs Cd comparisons, respectively. The integrated analyses of transcriptomic and metabolic data showed that 81 DEGs and 15 differentially expressed metabolites were involved in 20 NO-induced pathways. The dominant pathways were antioxidant activities such as glutathione metabolism, arginine and proline metabolism, secondary metabolites such as flavone and flavonol biosynthesis and phenylpropanoid biosynthesis, ABC transporters, and nitrogen metabolism. CONCLUSIONS: In general, the results revealed that there are three major mechanisms involved in NO-mediated Cd detoxification in tall fescue, including (a) antioxidant capacity enhancement; (b) accumulation of secondary metabolites related to cadmium chelation and sequestration; and (c) regulation of cadmium ion transportation, such as ABC transporter activation. In conclusion, this study provides new insights into the NO-mediated cadmium stress response.

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.

Phytohormones-induced senescence efficiently promotes the transport of cadmium from roots into shoots of plants: A novel strategy for strengthening of phytoremediation.

Due to the long growth period of plants, phytoremediation is time costly. Improving the accumulation of cadmium (Cd) in shoots of plants will promote the efficiency of phytoremediation. In this study, two senescence-relative phytohormones, abscisic acid (ABA) and salicylic acid (SA), were applied to strengthening phytoremediation of Cd by tall fescue (Festuca arundinacea S.). Under hydroponic culture, phytohormones treatment increased the Cd content of shoots 11.4-fold over the control, reaching 316.3 mg/kg (dry weight). Phytohormones-induced senescence contributes to the transport of heavy metals, and HMA3 was found to play a key role in this process. Additionally, this strategy could strengthen the accumulation of Cu and Zn in tall fescue shoots. Moreover, in soil pot culture, the strategy increased shoot Cd contents 2.56-fold over the control in tall fescue, and 2.55-fold over the control in Indian mustard (Brassica juncea L.), indicating its comprehensive adaptability and potential use in the field. In summary, senescence-induced heavy metal transport is developed as a novel strategy to strengthen phytoremediation. The strategy could be applied at the end of phytoremediation with an additional short duration (7 days) with comprehensive adaptability, and markedly strengthen the phytoremediation in the field.

Toxicity of soil labile aluminum fractions and aluminum species in soil water extracts on the rhizosphere bacterial community of tall fescue.

Different forms of aluminum (Al) in soil can be toxic to plants and the bacterial community. In our previous study, the distribution and toxicity to plants of soil Al species and soil labile Al fractions were examined. However, the toxicity of different forms of Al on the bacterial community has not been completely studied. In this study, five soil samples (pH: 4.92, 6.17, 6.62, 6.70, 8.51) were collected from Lichuan, China. Tall fescue was planted in rhizosphere boxes with those soils for 120 days. The toxicity of soil Al species and soil labile Al fractions on the bacterial community of near-rhizosphere (NR) soils and far-rhizosphere (FR) soils were analyzed. The effect of different forms of Al on bacterial community between NR and FR soils was small, but the difference was obvious according to the different spatial distribution of samples. An individual bacterial community has eosinophilia, and most bacterial communities are tolerant of heavy metals (e.g., Cu, Zn, Cd). The toxicity of exchangeable Al has a strong effect on the bacterial community. Meanwhile, the toxicity of Al3+ to the bacterial community is strong. In this study, the key finding was that the toxicity of the Al-F- complex toward the bacterial community and plants was different. AlF2+, AlF2+, AlF3, and AlF4- are toxic for the bacterial community, and the correlation decreases with the addition of F-. This finding is of considerable significance to the treatment of acid-contaminated soil and the study of the tolerance mechanism of plants toward Al.

Identification of ribosomal sites and karyotype analysis in Festuca ulochaeta Steud. and Festuca fimbriata Ness., grasses native to Brazil.

Festuca L. has more than 600 perennial species described, which makes it the largest genus within the family Poaceae. In Brazil, only two native species of Festuca have been described, for which cytogenetic studies need to be strengthened: Festuca ulochaeta and Festuca fimbriata. The aim of this study was to characterize the karyotypes of F. ulochaeta and F. fimbriata based on the mapping of rDNA sites. The FISH was performed with 35S and 5S rDNA probes. Both species have 42 chromosomes, of which 36 were metacentric and six were submetacentric. Festuca fimbriata has two pairs of 35S rDNA sites, one located on the metacentric pair 4, in an interstitial position, and one at the submetacentric pair 14 in the proximal position. Festuca ulochaeta has one pair of 35S rDNA in interstitial-proximal position in the metacentric pair 3. Both species showed 5S rDNA sites only on chromosome pair 21 in the terminal position of the short arm. The analysis of the chromosomal characteristics indicates that these species have a symmetrical karyotype and allopolyploid origin.

Study on the efficiency of phytoremediation of soils heavily polluted with PAHs in petroleum-contaminated sites by microorganism.

The effects of Fire Phoenix (a mixture of Festuca L.) and Purple coneflower (Echinacea purpurea (L.) Moench) on the remediation of two different high concentrations of PAH-contaminated soils were studied under the effect of strain N12 (Mycobacterium sp.), and the changes in rhizosphere enzymatic activity were preliminarily studied. The results of three culture stages (60 d, 120 d, and 150 d) showed that N12 has a promotional effect on the biomass of Fire Phoenix and E. purpurea, and the effect of N12 on the biomass of Fire Phoenix is better. Under the strengthening of N12, the maximum removal rates of Fire Phoenix reached 86.77% and 67.82% at two high PAH concentrations (A and B, respectively). The activity of dehydrogenase (DHO) is positively correlated with the degradation rate of PAHs at the A concentration (P < 0.05). The activity of DHO in soil will continue to increase at a higher level of the B concentration, but the positive correlation between the activity of DHO and the degradation rate of PAH is weakened. In the rhizosphere soil of the two plants, the change in polyphenol oxidase (PPO) activity with time has a significant negative correlation with the degradation rate of PAHs (P < 0.05). The experiment proved that Fire Phoenix is more suitable for the remediation of heavy PAH-contaminated soil under the condition of microorganism-strengthening, and it can achieve a better degradation effect when the concentrations of PAHs are < 150 mg·kg-1. Results provide a further scientific basis for the remediation of contaminated sites.

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.

Cadmium excretion via leaf hydathodes in tall fescue and its phytoremediation potential.

Cadmium (Cd) contamination of the soil is one of the most serious environmental problems of agricultural production. Phytoremediation has attracted increasing attention because it can safely remove the soil contaminates via plant uptake, accumulations and plant harvesting. However, the high Cd toxicity to plant tissues and treatment of the large amount of hazardous plant residues from phytoremediation have limited its commercial implementation. Here we show that the leaves of the tall fescue (Festuca arundinacea) can excrete Cd out to avoid Cd toxicity in plant tissues. Cd specific fluorescence spectroscopy with laser confocal scanning microscope, screening electron microscope with energy dispersive spectroscopy and guttation fluids analysis confirmed that leaf hydathodes were the pathway of Cd excretion in tall fescue. Element analysis showed that Cd was preferentially excreted out when compared to the ion nutrients. The amount of leaf Cd excretion was linearly increased in response to the Cd stress period. The phytoremediation efficiency was evaluated to remove 14.4% of soil Cd annually by the leaf Cd excretion in our experimental system. These findings indicate that a novel strategy of Cd phytoexcretion based on washing-off and collection of leaf surface Cd is feasible to avoid Cd toxic in plant tissues and the high treatment cost of hazardous plant residues.

Role of Festuca rubra and Festuca arundinacea in determinig the functional and genetic diversity of microorganisms and of the enzymatic activity in the soil polluted with diesel oil.

The objective of this study was to analyze the effect of two grass species, i.e. red fescue (Festuca rubra) and tall fescue (F. arundinacea), on the functional and genetic diversity of soil-dwelling microorganisms and on the enzymatic activity of soil not polluted and polluted with diesel oil. Grasses were examined for their effectiveness in accelerating degradation of PAHs introduced into soil with diesel oil. A growing experiment was conducted in Kick-Brauckman pots. The soil not polluted and polluted with diesel oil (7 cm3 kg-1 d.m.) was determined for the count of bacteria, colony development index, ecophysiological diversity index, functional diversity (using Biolog system), genetic diversity of bacteria (using NGS), enzymatic activity, and content of hydrocarbons. Study results demonstrated disturbed homeostasis of soil. The toxic effect of diesel oil on grasses alleviate with time since soil pollution. The yield of the first swath of red fescue decreased by 98% and that of tall fescue by 92%, whereas the yields of the second swath decreased by 82% and 89%, and these of the third swath by 50% and 47%, respectively. Diesel oil diminished also the functional and genetic diversity of bacteria. The use of grasses significantly decreased contents of C6-C12 (gasoline total), C12-C35 mineral oils, BTEX (volatile aromatic hydrocarbons), and PAHs in the soil, as well as enabled restoring the microbiological equilibrium in the soil, and increased functional and genetic diversity of bacteria. For this reason, both analyzed grass species, i.e. Festuca rubra and F. arundinacea, may be recommended for the remediation of soil polluted with diesel oil.

Young leaf protection from cadmium accumulation and regulation of nitrilotriacetic acid in tall fescue (Festuca arundinacea) and Kentucky bluegrass (Poa pratensis).

Phytoextraction efficiency of cadmium (Cd) contaminated soil mainly depended upon the mechanism of plants in absorption, translocation, distribution, and detoxification of Cd. A pot experiment was designed to investigate Cd distribution and accumulation among the different leaves of tall fescue (Festuca arundinacea) and Kentucky bluegrass (Poa pratensis) and its regulation by Nitrilotriacetic acid (NTA), a biodegradable chelating agent. The results showed that Cd concentrations in the senescent and dead leaves were 3.2 and 5.3 fold of that in the emerging leaves of tall fescue, and 19.3 and 25.1 fold of that in the emerging leaves of Kentucky bluegrass, respectively. The lower Cd concentrations were maintained in the emerging and mature leaves to avoid Cd toxicity. In the emerging and mature leaves, Cd was mainly accumulated in the vascular bundles and epidermis. No Cd dithizonate color was observed in the mesophyll tissues of Kentucky bluegrass and only minor Cd was observed in the mesophyll tissues of tall fescue. In the senescent leaves, Cd dithizonate complexes were located in the protoplasts and cell walls of all leaf tissues. NTA greatly promoted Cd translocation and distribution to the senescent and dead leaves of tall fescue, but no significant effect was observed in Kentucky bluegrass. Our results indicate that a young leaf protection mechanism might be involved in their Cd hypertolerance. The Cd preferential accumulation could lead a novel phytoextraction strategy by the continuously harvesting the senescent and dead leaves of tall fescue and Kentucky bluegrass.

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.

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.

Levels of Organic Compounds, Number of Microorganisms and Cadmium Accumulation in Festuca ovina Hydroponic Culture.

Understanding the microbiological, biochemical and physiological aspects of phytoremediation of soil and water environments polluted to different degrees with heavy metals has very important theoretical and practical implications. In this study, a comparison was made between total cadmium concentration in root and shoot tissues as well as concentrations of particular fractions of Cd immobilized by roots of Festuca ovina (Sheep's fescue) hydroponically cultivated in nutrient solutions supplemented with 1 µg Cd ml(­1) and those cultivated at 10 µg Cd ml(­1). After three weeks of F. ovina cultivation, the number of bacterial CFU and the amounts of organic chelators, siderophores, proteins and reducing sugars in the growth medium and on the root surface were higher at 10 than at 1 µg Cd ml(­1). The grass also reacted to the high Cd concentration by a decrease in plant growth and dehydrogenase activity in root tissues. The concentration of Cd determined in fractions bound with different strength in roots was significantly dependent on Cd concentration in the growth medium. When the plants were grown at 1 µg Cd ml(­1), 9% of the immobilized cadmium was loosely bound to the root surface, 20% was exchangeable adsorbed, and 28% was bound by chelation; at 10 µg Cd ml(­1), the respective values were 12%, 25%, and 20%. About 43% of the immobilized cadmium remained in roots after sequential extraction, and bioaccumulation factors in shoots had the same values independently of Cd concentration. At both Cd concentrations, the cadmium translocation index for F. ovina was low (< 1), which is why this grass can be recommended for phytostabilization of the metal under study.

Arbuscular mycorrhiza affects nickel translocation and expression of ABC transporter and metallothionein genes in Festuca arundinacea.

Mycorrhizal fungi are key microorganisms for enhancing phytoremediation of soils contaminated with heavy metals. In this study, the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (=Glomus mosseae) on physiological and molecular mechanisms involved in the nickel (Ni) tolerance of tall fescue (Festuca arundinacea = Schedonorus arundinaceus) were investigated. Nickel addition had a pronounced negative effect on tall fescue growth and photosynthetic pigment contents, as well as on AMF colonization. Phosphorus content increased markedly in mycorrhizal plants (M) compared to non-inoculated (NM) ones. However, no significant difference was observed in root carbohydrate content between AMF-inoculated and non-inoculated plants. For both M and NM plants, Ni concentrations in shoots and roots increased according to the addition of the metal into soil, but inoculation with F. mosseae led to significantly lower Ni translocation from roots to the aboveground parts compared to non-inoculated plants. ABC transporter and metallothionein transcripts accumulated to considerably higher levels in tall fescue plants colonized by F. mosseae than in the corresponding non-mycorrhizal plants. These results highlight the importance of mycorrhizal colonization in alleviating Ni-induced stress by reducing Ni transport from roots to shoots of tall fescue plants.

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.

Remediation of PAH-contaminated soil by the combination of tall fescue, arbuscular mycorrhizal fungus and epigeic earthworms.

A 120-day experiment was performed to investigate the effect of a multi-component bioremediation system consisting of tall fescue (Festuca arundinacea), arbuscular mycorrhizal fungus (AMF) (Glomus caledoniun L.), and epigeic earthworms (Eisenia foetida) for cleaning up polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. Inoculation with AMF and/or earthworms increased plant yield and PAH accumulation in plants. However, PAH uptake by tall fescue accounted for a negligible portion of soil PAH removal. Mycorrhizal tall fescue significantly enhanced PAH dissipation, PAH degrader density and polyphenol oxidase activity in soil. The highest PAH dissipation (93.4%) was observed in the combination treatment: i.e., AMF+earthworms+tall fescue, in which the soil PAH concentration decreased from an initial value of 620 to 41 mg kg(-1) in 120 days. This concentration is below the threshold level required for Chinese soil PAH quality (45 mg kg(-1) dry weight) for residential use.