Effects of exogenous melatonin on growth and physiological characteristics of Agropyron mongolicum seedlings under drought stress.

To clarify the alleviation effect of exogenous melatonin (MT) on Agropyron mongolicum under drought stress, we examined the response of A. mongolicum 'Yanchi' seedlings to simulated drought stress with polyethylene glycol 6000 (PEG-6000), by investigating the effects of exogenous addition of different concentrations (0, 1, 10, 50, 100, 150 and 200 mg·L-1) of MT on seedlings growth and physiological characteristics under drought stress. The results showed that drought stress significantly inhibited the growth of A. mongolicum seedlings, and that exogenous addition of different concentrations of MT could alleviate the growth inhibition caused by drought stress, with the strongest mitigation effect observed at MT concentration of 100 mg·L-1. Compared with the drought stress treatment alone, exogenous addition of 100 mg·L-1 MT under drought stress increased plant height, aboveground dry weight, and leaf relative water content by 58.2%, 121.2% and 48.1%. The contents of chlorophyll a, chlorophyll b, carotenoids increased by 48.7%, 80.8% and 38.3%, superoxide dismutase, peroxidase and root activity increased by 12.6%, 33.9% and 39.1%, and the contents of ascorbic acid and glutathione increased by 19.5% and 18.3%, respectively. The contents of proline, soluble sugar and soluble protein were increased by 16.2%, 32.6% and 14.3%, while that of malondialdehyde, hydrogen peroxide and superoxide anion radical were decreased by 45.8%, 65.8% and 30.8%, respectively. In summary, exogenous addition of 100 mg·L-1 MT could improve drought tolerance of A. mongolicum seedlings by promoting growth, enhancing antioxidant capacity, increasing the content of osmoregulation substances, inhibiting the excessive production of reactive oxygen, and reducing membrane peroxide level.

Nitrogen fertilization and CO2 concentration synergistically affect the growth and protein content of Agropyron mongolicum.

Background: The nitrogen (N) and protein concentrations in plant tissues exposed to elevated CO2 (eCO2) generally decline , such declines in forage grass composition are expected to have negative implications for the nutritional and economic value of grass. Plants require N for the production of a photosynthetically active canopy and storage proteins in the tissues, whose functionality will strongly influence productivity and quality. The objective of this study was to investigate whether eCO2 plus N-fertilization increases growth and N nutrition of Agropyron mongolicum, and the dependence of this improvement on the coordination between root and leaf development. Methods: We analyzed A. mongolicum from field-grown within the open-top chambers (OTCs) facility under two atmospheric CO2 (ambient, 400 ± 20 µmol mol-1, aCO2, and elevated, 800 ± 20 µmol mol-1, eCO2) and three N-fertigation treatments (control, low N-fertigation , and high N-fertigation) for two months. Results: Elevated CO2 plus N-fertigation strongly increased shoot and root biomass, and the nitrogen and protein concentrations of A. mongolicum compared to those plants at aCO2 levels. Increased N content in leaves and reduced specific leaf area (SLA) at a high N supply could alleviate photosynthetic acclimation to eCO2 and drive the production of greater shoot biomass with the potential for higher photosynthesis, productivity, and nutritional quality. The increased root length (RL), the ratio of total aboveground N taken up per RL (TN/RL), stomatal conductance (Gs), and transpiration rate (Tr) contribute to the transpiration-driven mass flow of N, consequently increasing N uptake by roots. In addition, a smaller percentage of N remained as unassimilated nitrate ( NO 3 - ) under eCO2, indicating that assimilation of NO 3 - into proteins was not inhibited by eCO2. These findings imply that grass productivity and quality will enhance under anticipated elevated CO2 concentration when effective management measures of N-fertilization are employed.

Salt stress triggers augmented levels of Na+, K+ and ROS alters salt-related gene expression in leaves and roots of tall wheatgrass (Agropyron elongatum).

In turfgrass breeding, competent grass ecotypes are preferably identified for their resistance to salinity condition. This research was designed to explore genes that induce salt resistance (NHX1, NHX2, HKT1;4, SnRK2.4 and NAC9) and their role in physiological modifications of six tall wheatgrass ecotypes (Agropyron elongatum L.). The sites of sample collection were characterized by different levels of salinity, i.e. low (EC: 4 dS m-1 and pH: 6.5), moderate (EC: 7 dS m-1 and pH: 6.5) and high (EC: 12 dS m-1 and pH: 7.5). This study was designed as a split-plot in a randomized complete block where salinity treatments served as the whole-plot factor and ecotypes served as the subplot factor. The ecotypes were screened for their resistance to salinity, based on visual symptoms, salt injury index, physiological features and biochemical parameters. The results revealed that ecotype 'AE5' was most resistant to salinity than other ecotypes, whereas 'AE3' was the most susceptible. To understand why these differences occurred, measurements were aimed at revealing mRNA levels that resulted from genes responsible for salt resistance. Our results demonstrated that salinity-resistant ecotypes showed high expression levels of several genes, i.e. NHX1, NHX2, HKT1;4, SnRK2.4 and NAC9 in the leaves and roots. These results were corroborated by a decrease (by 1.5-2.5 times) in stress markers, namely, superoxide anion (O2-), hydrogen peroxide (H2O2) and malondialdehyde (MDA), as well as an increase (by 0.5-7 times) in enzymatic and non-enzymatic antioxidant activity in salinity-resistant ecotypes when the plants were exposed to salinity. We observed higher values of initial root length and lateral root density (21% and 18%, respectively) in salinity-resistant ecotypes under salinity condition, compared to other ecotypes. There were lower expression levels of NHX1 and NHX2 in the roots, which were 3.2 and 2.1 times less, respectively, compared to the leaves. This implied that NHX1 and NHX2 expressions can lead to the sequestration of Na+ in the leaves during salinity condition. The current research revealed that HKT1;4 was more able to restrict Na + accumulation, compared to the actions of NHX1 and NHX2 genes. The over-expression of HKT1;4 in 'AE5' allowed a better maintenance of root growth during salinity condition. The expression of NAC9 had an increase of 2.1-fold which correlated with an increase in the amount of antioxidant enzymes. In general, the location of sample collection explained the differences in gene expression, especially regarding the extent to which plants respond to salinity condition. Ultimately, these differences can define physiological features in salinity-resistant and salinity-susceptible ecotypes of tall wheatgrass.

Nickel uptake and distribution in Agropyron cristatum L. in the presence of pyrene.

PAHs affect the uptake of heavy metal by plants. The uptake pathway, distribution and detoxification of nickel (Ni) in Agropyron cristatum L. (A. cristatum) were investigated in the presence of pyrene in this study. Most of Ni was adsorbed on the cell wall in the insoluble phosphate (57.31-72.18%) form and pectate and protein integrated (38.27-38.98%) form. Ni was transferred to the organelle (from 37.84% to 40.52%) in the presence of pyrene. The concentration of Ni in A. cristatum decreased by 27.42%; it was affected by the ATP production inhibitor and 29.49% by the P-type ATPase inhibitor. The results indicated that the uptake of Ni related closely to the synthesis and decomposition of ATP and was an active uptake process. Contents of phytochelatins (PCs) in A. cristatum in Ni contaminated soils increased by 19.97%, and an additional 4.13% increase occurred in the presence of pyrene when compared to single Ni contamination. The content of malic acid in A. cristatum was the highest for 262.78 mg g-1 in shoots and 46.81 mg g-1 in roots with Ni contamination. Besides, acetic acid in shoots and roots increased by 40.25% and 102.63% with Ni contamination, and by 61.59% and 185.71% with Ni-pyrene co-contamination. This study preliminarily explored the inhibitory mechanism of pyrene on plant uptake of Ni.

Chromosomal localization of genes conferring desirable agronomic traits from Agropyron cristatum chromosome 1P.

Agropyron cristatum (L.) Gaertn. (2n = 4x = 28, PPPP), a wild relative of common wheat, possesses many potentially valuable genes for wheat breeding. To transfer these genes into wheat, a series of wheat-A. cristatum derivatives have been obtained in our laboratory. In this study, a wheat-A. cristatum derivative II-3-1 was obtained, which was proven to contain a 1P (1A) disomic substitution and 2P disomic addition line with 40 wheat chromosomes and two pairs of A. cristatum chromosomes by genomic in situ hybridization (GISH) and molecular markers analysis. By further backcrossing with the wheat parent Fukuhokomugi (Fukuho) and self-fertilization, three different lines were separated from II-3-1, including wheat-A. cristatum 1P disomic addition line II-3-1a, 2P disomic addition line II-3-1b and 1P (1A) disomic substitution line II-3-1c. Because 2P addition line had been reported before, we aimed to investigate 1P disomic addition line II-3-1a and wheat-A. cristatum 1P (1A) disomic substitution line II-3-1c. Analysis of different genetic populations demonstrated that 1P chromosome harbored multiple agronomic traits, such as elevated spike length, increased tillering ability, reduced plant height and spikelet density. Besides, bristles on the glume ridges as an important morphological marker was located on 1P chromosome. Therefore, the novel 1P addition and substitution lines will be used as important genetic materials to widen the genetic resources of wheat.

Identification and characterization of high-molecular-weight glutenin subunits from Agropyron intermedium.

High-molecular-weight glutenin subunit (HMW-GS) is a primary determinant of processing quality of wheat. Considerable progress has been made in understanding the structure, function and genetic regulation of HMW-GS in wheat and some of its related species, but less is known about their orthologs in Agropyron intermedium, a useful related species for wheat improvement. Here seven HMW-GSs in Ag. intermedium were identified using SDS-PAGE and Western blotting experiments. Subsequently, the seven genes (Glu-1Aix1 ∼ 4 and Glu-1Aiy1 ∼ 3) encoding the seven HMW-GSs were isolated using PCR technique with degenerate primers, and confirmed by bacterial expression and Western blotting. Sequence analysis indicated that the seven Ag. intermedium HMW-GSs shared high similarity in primary structure to those of wheat, but four of the seven subunits were unusually small compared to the representatives of HMW-GS from wheat and two of them possessed extra cysteine residues. The alignment and clustering analysis of deduced amino acid sequences revealed that 1Aix1 and 1Aiy1 subunits had special molecular structure, belonging to the hybrid type compounding between typical x- and y-type subunit. The xy-type subunit 1Aix1 is composed of the N-terminal of x-type and C-terminal of y-type, whereas yx-type subunit 1Aiy1 comprises the N-terminal of y-type and C-terminal of x-type. This result strongly supported the hypothesis of unequal crossover mechanism that might generate the novel coding sequence for the hybrid type of HMW-GSs. In addition to the aforementioned, the other novel characteristics of the seven subunits were also discussed. Finally, phylogenetic analysis based on HMW-GS genes was carried out and provided new insights into the evolutionary biology of Ag. intermedium.

[Concentrations of different carbon and nitrogen fractions in rhizosphere and non-rhizosphere soils of typical plant species in mountainous area of southern Ningxia, Northwest China].

Taking the rhizosphere and non-rhizosphere soils of five typical plants Agropyron cristatum, Artemisia frigida, Pseudoraphis bungeana, Thymus mongolicus, and Artemisia sacrorum in a mountainous area of southern Ningxia as test objects, this paper studied their C and N forms contents. The C and N forms contents in the rhizosphere and non-rhizosphere soils differed with plant species. In the rhizosphere soil of A. sacrorum, the C content was the highest, with the total soil organic C (TOC), light fraction organic C (LFOC), and heavy fraction organic C contents being 22.94, 1.95, and 20. 88 g kg-1, respectively. In the rhizosphere soil of P. bungeana, the N content was the highest, with the total N (TN), mineralizable N (MN), and available N contents being 2.05 g kg-1 , 23.73 mg kg-1, and 11.99 mg kg-1 , respectively. In the rhizosphere soil of A. frigida, the LFOC/TOC and MN/TN ratios were the highest, which benefited the C and N transformed into more active forms. Light fraction organic C and mineralizable N could be used as the sensitive indicators of plant habitat change. For the five plant species, the contents of different C and N forms in the rhizosphere soil were generally higher than those in the non-rhizosphere soil.

Accumulation and tolerance characteristics of zinc in Agropyron cristatum plants exposed to zinc-contaminated soil.

In phytoremediation, plants are used to stabilize or remove toxins from soil. In this study, a pot experiment was conducted in a greenhouse to evaluate the phytoremediation potential of Agropyron cristatum (Poaceae) grown on Zinc (Zn) contaminated soils. Results indicated that Zn accumulation in both shoots and roots increased with soil Zn concentration, and Zn concentrations in roots were greater than in shoots. A significantly negative correlation was found between translocation factor or bioconcentration factor values and Zn concentrations in soil. Overall, A. cristatum was Zn excluder with an innate capacity to tolerate Zn stress and may have potential for the phytostabilization of sites contaminated with Zn.

Chelator-enhanced lead accumulation in Agropyron elongatum cv Szarvasi-1 in hydroponic culture.

Hydroponic culture was applied to compare the efficiency of K2EDTA and citrate in mobilizing Pb for accumulation in Agropyron elongatum cv. Szarvasi-1 and their effects on some physiological characteristics of the plants. The plants were grown in nutrient solutions containing 0, 10, and 100 microM Pb(NO3)2 combined with chelating agents added to the nutrient solutions after 21 days of growth, in 3 concentrations (0, 100, and 500 microM). The effects were measured after eight days. The energy grass proved to be greatly resistant to the treatments, as was reflected in the slight inhibition of growth, the resistance of the photosynthetic electron transport chain and the chlorophyll composition and the lack of change in the malone-dialdehyde content. Fundamental differences can be identified between the effects of EDTA and citrate. Citrate had only a little effect on the physiological parameters, which may be due to the strongly increasing lead accumulation with increasing concentration of Pb in the nutrient solution. Additionally, citrate ensured a higher biomass yield with higher shoot Pb accumulation compared to EDTA in almost all treatments. Concerning biomass reduction, 10 microM Pb applied together with K2EDTA has the most deleterious effects on energy grass. The effects correlated with the concentration of EDTA.

The protein kinase MEK1/2 participates in the regulation of ascorbate and glutathione content by jasmonic acid in Agropyron cristatum leaves.

This study investigated the role of the protein kinase MEK1/2 in the regulation of ascorbate and glutathione content by jasmonic acid in Agropyron cristatum leaves. The results showed that JA induced increases in the transcript levels and activities of APX, GR, MDHAR, DHAR, GalLDH and γ-ECS, the contents of AsA, GSH, total ascorbate and total glutathione, and the ratios of AsA/DHA and GSH/GSSG, and reduced the E(GSSG/2GSH). The increases, except for the transcript level and activity of γ-ECS and the reduction in E(GSSG/2GSH,) were all suppressed by pre-treatment with the MEK1/2 inhibitors PD98059 and U0126. The results of western blot analyses showed that JA induced increases in the phosphorylation level of MEK1/2. Our results suggest that JA could induce the activation of MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the up-regulation of ascorbate and glutathione content in A. cristatum leaves.

Effects of pig manure compost and nonionic-surfactant Tween 80 on phenanthrene and pyrene removal from soil vegetated with Agropyron elongatum.

This paper evaluates the effects of pig manure compost (PMC) and Tween 80 on the removal of phenanthrene (PHE) and pyrene (PYR) from soil cultivated with Agropyron elongatum. Soils spiked with about 300 mg kg(-1) of PHE and PYR were individually amended with 0%, 2.5%, 5% and 7.5% (dry wt) of PMC or 0, 20 and 100 mg kg(-1) of Tween 80. Unplanted and sterile microcosms were prepared as the controls. PAH concentration, total organic matter (TOM), dissolved organic carbon (DOC), total heterotrophic and PAH degrading microbial populations in soil were quantified before and after 60d period. The results indicated that A. elongatum could significantly enhance PYR removal (from 46% to 61%) but had less impact on PHE removal (from 96% to 97%). Plant uptake of the PAHs was insignificant. Biodegradation was the key mechanism of PAH removals (<3% losses in the sterile control). Increase in PMC or Tween 80 levels increased the removal of PYR but not of PHE. Maximal PYR removal of 79% and 92% were observed in vegetated soil receiving 100 mg kg(-1) Tween 80 and 7.5% PMC, respectively. Enhanced PYR removal in soil receiving PMC could be explained by the elevated levels of DOC, TOM and microbial populations as suggested by Pearson correlation test. While the positive effect of Tween 80 on PYR removal could probably due to its capacities to enhance PYR bioavailability in soil. This paper suggests that the addition of either PMC or nonionic-surfactant Tween 80 could facilitate phytoremediation of PAH contaminated soil.

Fate of 14C-Pyrene in soil-plant system amended with pig manure compost and Tween 80: a growth chamber study.

This paper evaluated the effects of a pig manure compost (PMC) and a nonionic surfactant Tween 80 on the fate of 14C-Pyrene (Pyr) in a soil-plant system (Agropyron elongatum). Soils spiked with 14C-4, 5, 9, 10-Pyr were amended with 7.5% (w/w) PMC together with or without 100mgkg(-1) of Tween 80. Unplanted soil without amendments was set as the control. Gas phases of the systems were monitored for 14CO2 over a 60 days period. The impact of PMC and Tween 80 on the apparent loss of the PAH and the distribution of 14C-activity in the systems was studied. 14C-activity associated with different soil fractions was further examined by using methyl-isobutyl-ketone (MIBK) fractionation method. The results showed that the addition of PMC could increase the dissipation of Pyr in vegetated soil from 12.1% to 58.7%, while the co-addition of Tween 80 and PMC could further enhance the dissipation to 90.3%. Pyr dissipation in soil was correlated with the mineralization of 14C-Pyr, indicating that Pyr dissipation was mainly due to mineralization. A higher formation of water-extractable metabolites was observed in soil amended with PMC and Tween 80, and this was correlated with a higher biomass accumulation of 14C-activity and higher bound residue formation in the soil. Overall, this study suggested that the co-application of PMC and Tween 80 could improve phytoremediation of Pyr-contaminated soil.

Proteomic analysis on a high salt tolerance introgression strain of Triticum aestivum/Thinopyrum ponticum.

Soil salinity is a major abiotic constraint to agricultural productivity. We successfully bred a new common wheat (Triticum aestivum L.) introgression variety (Shanrong No. 3) with high salt-tolerance via asymmetric somatic hybridization between common wheat cultivar (Jinan 177) and UV-irradiated Agropyron elongatum (Thinopyrum ponticum Podp). We report here a comparative proteomic analysis to investigate variety-specific and salt-responsive proteins between seedling-roots of Shanrong No. 3 and Jinan 177. In total, 114 spots reproducibly presented differential expression patterns on 2-DE maps. Of them, 34 were variety-specific and 49 were salt-responsive. We identified 110 spots by MALDI-TOF MS and partially confirmed by MALDI-TOF-TOF MS, and functionally classified them into signal transduction, transcription and translation, transporting, chaperones, proteolysis and detoxification, etc. Meanwhile, we also found the alteration of protein expression of Shanrong No. 3 through inhibition of old proteins and production of novel ones, change in abundance and sensitivity of some nonsalt-responsive and salt-responsive proteins, as well as PTMs. Furthermore, comparison between proteome and transcripteome using cDNA microarray showed that there were only 20 proteins with abundances correlative to signal densities of corresponding EST probes. This study gives us a global insight into proteomic difference between Shanrong No. 3 and Jinan 177 in constitute and to salt-response.

Mineralization and plant uptake of 14C-labeled nonylphenol, nonylphenol tetraethoxylate, and nonylphenol nonylethoxylate in biosolids/soil systems planted with crested wheatgrass.

Microcosm experiments (duration, 150 d) were conducted to evaluate the mineralization and plant uptake of [14C]nonylphenol (NP), [14C]nonylphenol tetraethoxylate (NPE4), and [14C]nonylphenol nonylethoxylate (NPE9) in a soil/biosolids (99.5:0.5 w/w) environment planted with crested wheatgrass (Agropyron cristatum). Three initial nominal concentrations (6, 24, and 47 mg/kg dry wt) each of NP, NPE4, and NPE9 were examined along with unplanted and unplanted poisoned controls. Phenol (22 mg/kg) also was evaluated as a more degradable reference compound. The biosolids were obtained from a municipal treatment plant, and the loamy sand soil was freshly collected. Mineralization ranged from 7% for NP to 53% for phenol, and no enhancement was observed in the planted systems. For NP, NPE4, and NPE9, 14C foliar tissues concentrations were proportional to exposure concentrations but were 10-fold lower than the root concentrations and two- to threefold lower than the soil concentrations. Bioconcentration factors (BCFs) based on 14C measurements ranged from 0.31 (mg compound/kg dry plant/ mg compound/kg dry soil) for systems spiked with NP to 0.52 for systems spiked with NPE9. Results of the NP analysis (initial concentration, 47 mg/ kg) showed a 90% decrease in the soil concentration and an average BCF of 1.0. The lower BCF calculated from the 14C analysis likely resulted from the presence of NP transformation products in the soil that are less available or are translocated by the plants but quantified by the combustion/liquid scintillation counting procedure.

Biocontrol and PGPR features in native strains isolated from saline soils of Argentina.

A bacterial collection of approximately one thousand native strains, isolated from saline soils of Cordoba province (Argentina), was established. From this collection, a screening to identify those strains showing plant growth promotion and biocontrol activities, as well as salt tolerance, was performed. Eight native strains tolerant to 1 M: NaCl and displaying plant growth promotion and/or biocontrol features were selected for further characterization. Strains MEP(2 )18, MRP(2 )26, MEP(2 )11a, MEP(3 )1, and MEP(3 )3b significantly increased the growth of maize seedlings under normal and saline conditions, whereas isolates ARP(2 )3, AEP(1 )5, and ARP(2 )6 were able to increase the root dry weight of agropyre under saline conditions. On the other hand, strains MEP(2 )18 and ARP(2 )3 showed antagonistic activity against phytopathogenic fungi belonging to Sclerotinia and Fusarium genus. Antifungal activity was found in cell-free supernatants, and it was heat and protease resistant. Strains MEP(2)18 and ARP(2)3 were identified as Bacillus sp. and strains MEP(2)11a and MEP(3)3b as Ochrobactrum sp. according to the sequence analysis of 16S rRNA gene.

Overexpression of AeNHX1, a root-specific vacuolar Na+/H+ antiporter from Agropyron elongatum, confers salt tolerance to Arabidopsis and Festuca plants.

Agropyron elongatum, a species in grass family, has a strong tolerance to salt stress. To study the molecular mechanism of Agropyron elongatum in salt tolerance, we isolated a homolog of Na(+)/H(+) antiporters from the root tissues of Agropyron plants. Sequence analysis revealed that this gene encodes a putative vacuolar Na(+)/H(+) antiporter and was designated as AeNHX1. The AeNHX1-GFP fusion protein was clearly targeted to the vacuolar membrane in a transient transfection assay. Northern analysis indicated that AeNHX1 was expressed in a root-specific manner. Expression of AeNHX1 in yeast Na(+)/H(+) antiporter mutants showed function complementation. Further, overexpression of AeNHX1 promoted salt tolerance of Arabidopsis plants, and improved osmotic adjustment and photosynthesis which might be responsible for normal development of transgenic plants under salt stress. Similarly, AeNHX1 also functioned in transgenic Festuca plants. The results suggest that this gene might function in the roots of Agropyron plants, and its expression is involved in the improvement of salt tolerance.

Growth of Agropyron elongatum in a simulated nickel contaminated soil with lime stabilization.

A greenhouse study was performed to evaluate the feasibility of using Agropyron elongatum and lime treatment for remediation of a simulated nickel (Ni) contaminated acidic soil. The acid soil was spiked with four levels of Ni, i.e., 0, 15, 50, and 100 mg Ni kg(-1) soil and the soil pH at each Ni level was adjusted to 4, 6 and 8 by liming with CaO. Addition of lime raised the soil pH and resulted in a decrease in concentrations of DTPA-extractable and water-soluble Ni in the soil, with a maximum reduction of 64 and 28 mg kg(-1), respectively at the highest level of Ni treatment as compared to the control without Ni treatment. In general, excessive Ni content in soil, especially at pH 4 inhibited the growth of Agropyron. Liming improved the growth condition and the highest dry weight yield of 12 g pot(-1) was obtained in soil spiked with 15 mg Ni kg(-1) at pH 6; and at the highest level of Ni, the dry weight yield increased from 0.48 to 5.96 g pot(-1) when the pH was increased from 4 to 6. However a further increase in pH to 8 did not improve plant yield because of the unavailability of nutrients at such a high pH. Nickel contents in plant were positively correlated to soil Ni contents at each respective pH level. Most of the Ni taken up by Agropyron was retained in the roots and the highest Ni uptake by plant was 3.9 mg pot(-1) in soil spiked with 100 mg Ni kg(-1) at pH 5.9, which was about 2.6% of total Ni added to the soil. This implies that Agropyron is not a hyperaccumulating species but is highly tolerant. Lime amendment together with the tolerant characteristic of Agropyron could provide a possible means to remediate Ni contaminated soils through phytostabilization.

[Genome constitution of Agropyron elongatum 4x by biochemical and SSR markers].

We analyzed the electrophoritic patterns of 16 kinds of isozyme and three kinds of storage protein in Agropyron elongatum 2x and Ag. elongatum 4x by isoelectric focusing (IEF) and SDS-PAGE, respectively. The results showed three types of electrophoritic patterns. In the first type, the zymogram phenotypes are identical between Ag. elongatum 2x and Ag. elongatum 4x. Two kinds of isozyme belong to this type, which accounts for 10.5% of all the biochemical markers analyzed. In the second type, Ag. elongatum 4x showed a phenotype which is made up of combinations of the all of Ag. elongatum 2x bands and the specific bands. Ten kinds of isozyme and three kinds of storage protein fall into this class, which is the most part and accounts for 63.2% of all the markers analyzed. In the third type, Ag. elongatum 2x and Ag. elongatum 4x showed some identical bands and their own specific bands. Five kinds of isozyme were classified to this group,which accounts for 26.3% of all the markers analyzed. The results above suggested that Ag. elongatum 4x is a allotetraploid composed of one genome originated from Ag. elongatum 2x and another unknown genome which is apparently distinct from the St, J and N genomes of relative species. Otherwise, SSR primers were used to analyze the relation of Ag. elongatum 2x and Ag. elongatum 4x. The amplification results of most primers showed that Ag. elongatum 2x and Ag. elongatum 4x have some identical bands and Ag. elongatum 4x have some specific bands. This result validated the conclusion from biochemical marker analyses that Ag. elongatum 4x is a allotetraploid.

Uptake of nonylphenol and nonylphenol ethoxylates by crested wheatgrass.

Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids often are land applied, but little is known regarding the potential uptake of biosolid-derived contaminants by plants. Hydroponic experiments, 11 to 14 weeks in duration, were conducted to examine the uptake and translocation of 14C and unlabeled NP, nonylphenol tetraethoxylate (NPE4), and nonylphenol nonylethoxylate (NPE9) by crested wheatgrass (Agropyron cristatum). Phenol also was evaluated for comparison. Plant tissue was analyzed for 14C and for the parent compounds. Volatilization from the hydroponic system and rhizosphere mineralization also were quantified. At the conclusion of the study, most of the plant-associated 14C was found in the roots (NP = 98%, NPE4 = 92%, and NPE9 = 81%). Concentrations of 14C in the foliar tissue ranged from 0.002 to 0.045 mg-equivalent per kg (dry wt), but no parent compounds were detected, implying that the 14C was unextractable or in the form of metabolites. Transpiration stream concentration factors for NP, NPE4, and NPE9, calculated assuming the 14C was parent compound, were 0.012, 0.032, and 0.066, respectively. Little mineralization was observed for NP, NPE4, and NPE9 in the hydroponic system; however, for phenol, 16 to 30% of the added 14C was mineralized.

[Comparative study on daily change of photosynthesis rate of the rhizomatous grasses in milky ripe stage].

Comparative study on daily change of photosynthesis rate of the rhizomatous grasses in their milky ripe stage was carried out, and the results showed that photosynthetic rate of five grasses appeared to be two-apex curve, except Elytrigia intermedia appeared to be one-apex curve. The general trend was that the higher the root/shoot ratio was, the later the first apex of the photosynthetic rate reached, and the shorter the noon break period was. Moreover, low relative humidity and high leaf temperature were the important factors for noon break. Leymus chinense, Pascopyrum smithii Rydb. cn. Rosana, Leymus secalinus, Leymus racemosus, Agropyron mongolicum and Elytrigia intermedia reached the first apex at 10:12, 10:00, 9:51, 9:39, 9:06 and 8:13, the noon break period was 471, 474, 464, 467 and 551 min, and the average leaf temperature during noon break was 37.8, 37.5, 36.9, 37.0 and 36.3 degrees C, respectively. Leymus chinense and Agropyron mongolicum, Leymus secalinus and Leymus racemosus had similar daily change in photosynthetic rate, respectively, and their r values were 0.88 and 0.96 respectively when R = 0.01.