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The application of phytohormones is a viable technique to increase the efficiency of phytoremediation in heavy metal-contaminated soils. The objective of this study was to determine how the application of 24-epibrassinolide (EBR), a brassinosteroid analog, could regulate root growth and tolerance to cadmium (Cd) stress in Kentucky bluegrass. As a result, the number of lateral root primordia and total root length in the Cd-treated seedlings decreased by 33.1 % and 56.5 %, respectively. After the application of EBR, Cd accumulation in roots and leaves, and the negative effect of Cd on root growth were reduced under Cd stress. Additionally, the expression of the brassinosteroid signaling gene PpBRI1 was significantly upregulated by exogenous EBR. Moreover, exogenous EBR upregulated the expression of genes encoding antioxidant enzymes and improved the activity of antioxidant enzymes, thereby reduced oxidative stress in roots. Finally, targeted hormonomics analysis highlighted the utility of the application of EBR to alleviate the effect of Cd on the reduction in auxin (IAA) content and the increase in ethylene (ACC) content. These were known to be associated with the upregulation in the expression of auxin biosynthesis gene PpYUCCA1 and downregulation in the expression of ethylene biosynthesis gene PpACO1 in the roots treated with Cd stress. Overall, the application of EBR alleviated Cd-induced oxidative stress in addition to improving root elongation and lateral root growth crosstalk with auxin and ethylene in Kentucky bluegrass subjected to Cd stress. This study further highlights the potential role of brassinosteroids in improving the efficiency of phytoremediation for Cd-contaminated soils. [Display omitted] • Cd stress inhibited root elongation and lateral root growth of Kentucky bluegrass. • Exogenous 24-epibrassinolide (EBR) alleviated Cd-induced inhibition in root phenotype. • EBR activated BRs signal transduction by upregulating the expression of PpBRI1. • EBR interacted with auxin and ethylene to improve lateral root growth under Cd stress. • Enzymatic antioxidants were enhanced by exogenous EBR to reduce ROS in Cd-treated roots. [ABSTRACT FROM AUTHOR]

Background: Kentucky bluegrass (Poa pratensis L.) is a prominent turfgrass in the cool-season regions, but it is sensitive to salt stress. Previously, a relatively salt tolerant Kentucky bluegrass accession was identified that maintained green colour under consistent salt applications. In this study, a transcriptome study between the tolerant (PI 372742) accession and a salt susceptible (PI 368233) accession was conducted, under control and salt treatments, and in shoot and root tissues. Results: Sample replicates grouped tightly by tissue and treatment, and fewer differentially expressed transcripts were detected in the tolerant PI 372742 samples compared to the susceptible PI 368233 samples, and in root tissues compared to shoot tissues. A de novo assembly resulted in 388,764 transcripts, with 36,587 detected as differentially expressed. Approximately 75 % of transcripts had homology based annotations, with several differences in GO terms enriched between the PI 368233 and PI 372742 samples. Gene expression profiling identified salt-responsive gene families that were consistently down-regulated in PI 372742 and unlikely to contribute to salt tolerance in Kentucky bluegrass. Gene expression profiling also identified sets of transcripts relating to transcription factors, ion and water transport genes, and oxidation-reduction process genes with likely roles in salt tolerance. Conclusions: The transcript assembly represents the first such assembly in the highly polyploidy, facultative apomictic Kentucky bluegrass. The transcripts identified provide genetic information on how this plant responds to and tolerates salt stress in both shoot and root tissues, and can be used for further genetic testing and introgression. [ABSTRACT FROM AUTHOR]

To figure out current landscaping of Tibet, analyze local garden landscaping quantitatively, and solve greening problems, this paper adopted "five-point sampling method" for the stratified survey of garden plant communities, investigated species and application of garden plants in Tibet comprehensively, discussed current situation, characteristics and problems of local landscaping, and proposed corresponding measures. According to the investigation, (1) There arc 368 applied garden plant species (including varieties) of 207 genera, 91 families; (2) In the tree layer, shrub layer and herb layer, Picea likiangensis var. likiangensis, Buxus megistophylla, Poa pratensis have the highest importance value, i.e., 43.050, 25.128, 45.950; (3) The most applied families in local landscaping are Rosaceae (53), Salicaceae (23), Compositae (21), Leguminosae (20), Gramineae (19), Pinaceae (16), Oleaceae (14) and Cupressaceae (12), accounting for 14.40%, 6.25%, 5.71%, 5.43%, 5.16%, 4.35%, 3.80% and 3.26% of the total, respectively; (4) The total landscaping level is poor and uneven, application of landscaping plants varies greatly among regions, garden application is poor; (5) Proportion of garden landscapes is unreasonable. [ABSTRACT FROM AUTHOR]

A common complaint of ecological restoration is there have been few systematic analyses of past restorations which has led to a lack of evidence informing future restorations. An analysis was done on 123 past native grassland reconstructions, spanning the last 40 years, in eastern North Dakota and northwestern Minnesota. A cluster analysis and indicator species analysis were used to place the 123 surveyed reconstructions into five significantly different groups. The five groups were separated into a Native group with the sub-groups, Big Bluestem Dominated (BBD) and Native Grass Mix (NGM) having native species as indicators, and an Exotic group with two exotic grasses, smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis), being indicators. Thirty-eight percent of the reconstructions were classified as Exotic. A logistic regression was used to assign membership probability to the Native group based on: 1) seed mix species richness; 2) number of grass species in the seed mix; 3) percent of grasses in seed mix; 4) time of year when seeded; and 5) seeding method. The probability of membership to the Native group for dormant season seeding, broadcast seeding, and 20+ species natives seed mix was 100%, 74%, and 81%, respectively. The probabilities of the different practices in relation to the reconstruction outcomes will provide evidence for managers on how to plan for future reconstructions. [ABSTRACT FROM AUTHOR]

Kentucky bluegrass ( Poa pratensis L.) is one of the most widely used turfgrasses for home lawns, golf courses, parks, and athletic fields in temperate climates. Oxidative stress caused by drought stress is a major limiting factor for grass cultivation in arid and semi-arid regions. The objective of this study was to investigate whether Prohexadione-Calcium (Pro-Ca) may play a role in promoting drought tolerance in kentucky bluegrass. Pro-Ca was exogenously applied as a foliar spray at the rate of 0, 7.5, 15 or 25 mg a.i./m² to well established kentucky bluegrass under wellwatered (100 of field capacity) or drought-stressed (70 and 40% of field capacity) conditions. The effect of Pro-Ca on the growth physiology, drought stress response, antioxidant activity, and lipid peroxidation of kentucky bluegrass exposed to drought stress was measured during 28 days at 7 days interval. Pro-Ca treated kentucky bluegrass exposed to drought stress had higher relative water content (RWC) and turf quality, and lower electrolyte leakage and malondialdehyde (MDA) content as membrane integrity indicators, compared with untreated plants. Pro-Ca application significantly increased the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities under well-watered and drought conditions, but this increase is more evident in drought stressed plants. Pro- Ca application at 15 mg/m² was found to be more effective in alleviating drought stress damage in kentucky bluegrass. The results from this study suggest that Pro-Ca enhanced drought stress tolerance in kentucky bluegrass by maintaining higher RWC and membrane stability. [ABSTRACT FROM AUTHOR]

Interspecific hybridization between Poa arachnifera Torr. (Texas bluegrass) and Poa pratensis L. (Kentucky bluegrass) has shown to be a proven method for the development of turf-type hybrid bluegrass cultivars for the southern United States. Unlike in P. pratensis, the use of DNA markers for molecular characterization and flow cytometry to determine nuclear DNA contents has not been extensively utilized in P. arachnifera. In this study, 2C nuclear DNA content of 19 different genotypes of P. arachnifera (both males and females) was determined to range from 8.02 to 13.24 pg/2C using flow cytometry. The DNA content of the hybrids between P. arachnifera and P. pratensis from two different pedigrees was found to be intermediate between their parents. Furthermore, the utility of the trx (thioredoxin-like) nuclear gene in the identification of interspecific hybrids between P. arachnifera and P. pratensis was demonstrated using sequence and phylogenetic analyses. A newly discovered 851-bp trx allele may serve as a useful marker to differentiate P. arachnifera from P. pratensis and provide insights into the evolutionary origin of P. arachnifera. [ABSTRACT FROM AUTHOR]

Rusts are destructive fungal diseases that can cause severe thinning and unattractive discoloration of kentucky bluegrass (KBG; Poa pratensis L.). Currently, turfgrass breeding programs rely on field evaluations to screen KBG germplasm for rust resistance; methods that are expensive, labor intensive, and require large turf areas. The availability of a greenhouse-based assay to perform prescreening of KBG germplasm for resistance to rust diseases before field trials would allow breeders to remove the poorest performing plants before field evaluations thus enhancing breeding efficiency. In this study, we set out to develop a reliable, low-cost greenhouse inoculation protocol for the two most common rust pathogens of KBG in temperate growing regions: Puccinia coronata and Puccinia graminis, the causal agents of crown and stem rust, respectively. Using a modified inoculation assay and custom-built plexi-glass chambers adapted from protocols used for cereal rust pathogens, urediniospores of crown and stem rust fungi developed on inoculated plants 10 to 14 days postinoculation. Real-time polymerase chain reaction (PCR) assays, disease symptomology, and morphology of urediniospores confirmed the presence and identity of both rust pathogens from inoculated host tissue. The inoculation protocols described here represent an effective method to accelerate screening of KBG germplasm for resistance to crown and stem rust diseases. Infection of KBG plants in the greenhouse will also allow breeders to maintain populations of crown and stem rust fungi throughout the year, providing a reliable and ongoing source of pathogen inoculum for experimentation and screening in the future. [ABSTRACT FROM AUTHOR]

In Kentucky bluegrass (Poa pratensis), Claviceps purpurea, the causal agent of ergot, typically releases ascospores during the early-morning hours, between about midnight and 10:00 a.m., corresponding to time of flowering, when the unfertilized ovaries are most susceptible to infection. During aeromycology studies of C. purpurea in perennial ryegrass (Lolium perenne) in northeastern Oregon during 2008 to 2010 and 2013, a strain of C. purpurea was found that released ascospores in the afternoon, coinciding with flowering in perennial ryegrass. Under controlled environmental conditions, sclerotia from perennial ryegrass and Kentucky bluegrass released spores in the afternoon and morning, respectively, consistent with timing of spore release under field conditions. Internal transcribed spacer (ITS) sequences of single sclerotial isolates from Kentucky bluegrass and peremiial ryegrass were consistent with C. purpurea, although minor variations in ITS sequences among isolates were noted. Differences between Kentucky bluegrass and perennial ryegrass isolates were observed in random amplified polymorphic DNA. Evidence is provided for adaptation of C. purpurea to perennial ryegrass by means of delayed spore release that coincides with afternoon flowering in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Kentucky bluegrass ( Poa pratensis L.) is a very common grass species with a wide distribution, including in Mediterranean areas. The objective of this study was to investigate the effects of non-clavicipitaceous fungal endophytes on forage production by P. pratensis, and on the nutritive value and mineral status of its herbage. Plants were inoculated with each of eight endophytic species and grown under greenhouse conditions. After 3 months, the plants were harvested and dried before evaluating the following parameters: dry mass of herbage and roots, crude protein content, neutral detergent fibre content, and mineral contents in herbage. The results showed that endophytes affected the biomass yield (herbage and roots), fibre content, and mineral contents in the forage. Compared with controls, plants inoculated with Stemphylium globuliferum showed the highest herbage and root biomass values, whilst those inoculated with Embellisia leptinellae and S. globuliferum showed reduced fibre contents in herbage. Plants infected with Epicoccum nigrum and S. globuliferum showed increased herbage concentrations of calcium, magnesium, molybdenum, and titanium. These results demonstrate that inoculation of Poa pratensis with endophytes can increase its biomass yield and the nutritive value of its herbage. Therefore, endophyte inoculation may be a useful strategy to reduce nutrient deficiencies in P. pratensis forage. [ABSTRACT FROM AUTHOR]

Adequate turfgrass sod strength for harvesting and handling is typically determined by the producer's past experience and subjective appraisal. This study was conducted to determine the relationship between producer subjective sod-strength assessments and quantitative shear-strength measurements with predominantly kentucky bluegrass (Poa pratensis L.) turf. Across three consecutive growing seasons, 93 samples were collected from sod fields in Rhode Island and assessed for sod strength by subjective and quantitative methods. Producer subjective ratings of sod strength were significantly (P < 0.0001) associated with quantitative measurements of peak force required to shear a sod strip. Minimally acceptable strength occurred most frequently when peak shear force was between 55 and 85 kg⋅m-1 width of sod; whereas preferred sod strength occurred most frequently when peak shear force was between 70 and 140 kg⋅m-1 width of sod. Once peak force exceeded 58 and 86 kg⋅m-1, there was a > 50% probability that sod strength would be judged at least adequate and at preferred strength, respectively, up to a peak force of 140 kg⋅m-1. The results suggest that quantitative measurements of shear strength can be related to producer subjective assessments, and provide unbiased benchmark values to guide management decisions for kentucky bluegrass sod production. [ABSTRACT FROM AUTHOR]

Dehydration-Responsive Element Binding proteins (DREB)/C-repeat (CRT) Binding Factors (CBF) have been identified as transcriptional activators during plant responses to cold stress. The objective of this study was to determine the physiological roles of a CBF gene isolated from a cold-tolerant perennial grass species, Kentucky bluegrass (Poa pratensis L.), which designated as PpCBF3, in regulating plant tolerance to freezing stress. Transient transformation of Arabidopsis thaliana mesophyll protoplast with PpCBF3-eGFP fused protein showed that PpCBF3 was localized to the nucleus. RT-PCR analysis showed that PpCBF3 was specifically induced by cold stress (4°C) but not by drought stress [induced by 20% polyethylene glycol 6000 solution (PEG-6000)] or salt stress (150 mM NaCl). Transgenic Arabidopsis overexpressing PpCBF3 showed significant improvement in freezing (-20°C) tolerance demonstrated by a lower percentage of chlorotic leaves, lower cellular electrolyte leakage (EL) and H2O2 and O2.- content, and higher chlorophyll content and photochemical efficiency compared to the wild type. Relative mRNA expression level analysis by qRT-PCR indicated that the improved freezing tolerance of transgenic Arabidopsis plants overexpressing PpCBF3 was conferred by sustained activation of downstream cold responsive (COR) genes. Other interesting phenotypic changes in the PpCBF3-transgenic Arabidopsis plants included late flowering and slow growth or ‘dwarfism’, both of which are desirable phenotypic traits for perennial turfgrasses. Therefore, PpCBF3 has potential to be used in genetic engineering for improvement of turfgrass freezing tolerance and other desirable traits. [ABSTRACT FROM AUTHOR]

Temperature is a predominant environmental factor affecting grass germination and distribution. Various thermal-germination models for prediction of grass seed germination have been reported, in which the relationship between temperature and germination were defined with kernel functions, such as quadratic or quintic function. However, their prediction accuracies warrant further improvements. The purpose of this study is to evaluate the relative prediction accuracies of genetic algorithm (GA) models, which are automatically parameterized with observed germination data. The seeds of five P. pratensis (Kentucky bluegrass, KB) cultivars were germinated under 36 day/night temperature regimes ranging from 5/5 to 40/40°C with 5°C increments. Results showed that optimal germination percentages of all five tested KB cultivars were observed under a fluctuating temperature regime of 20/25°C. Meanwhile, the constant temperature regimes (e.g., 5/5, 10/10, 15/15°C, etc.) suppressed the germination of all five cultivars. Furthermore, the back propagation artificial neural network (BP-ANN) algorithm was integrated to optimize temperature-germination response models from these observed germination data. It was found that integrations of GA-BP-ANN (back propagation aided genetic algorithm artificial neural network) significantly reduced the Root Mean Square Error (RMSE) values from 0.21~0.23 to 0.02~0.09. In an effort to provide a more reliable prediction of optimum sowing time for the tested KB cultivars in various regions in the country, the optimized GA-BP-ANN models were applied to map spatial and temporal germination percentages of blue grass cultivars in China. Our results demonstrate that the GA-BP-ANN model is a convenient and reliable option for constructing thermal-germination response models since it automates model parameterization and has excellent prediction accuracy. [ABSTRACT FROM AUTHOR]

To improve the salinity tolerance of turfgrass and investigate the effect of spermidine (Spd) on antioxidant metabolism and gene expression under salinity stress condition, exogenous Spd was applied before two kentucky bluegrass ( Poa pratensis L.) cultivars (‘Kenblue’ and ‘Midnight’) were exposed to 200 mM sodium chloride (NaCl) stress for 28 d. Salinity stress decreased the turfgrass quality, increased the content of malonyldialdehyde (MDA), superoxide anion (O 2 ·− ) and hydrogen peroxide (H 2 O 2 ), and enhanced activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD) and ascorbate peroxidase (APX) and isozymes intensity in both cultivars. In addition, the expression level of Cu/ZnSOD was down-regulated in ‘Kenblue’ but up-regulated in ‘Midnight’ after salt treatment. Salinity stress also enhanced the expression of APX but inhibited the expression of CAT and POD in both cultivars. Exogenous Spd treatment alleviated the salinity-induced oxidative stress through decreasing MDA, H 2 O 2 and O 2 ·− contents in both cultivars. Besides, exogenous Spd further enhanced the activities of SOD, CAT, POD and APX accompanied with the increased intensity of specific isozymes of SOD, CAT and APX in both cultivars and POD in ‘Kenblue’. Moreover, Spd further up-regulated expression levels of Cu/ZnSOD and APX , but down-regulated those of CAT and POD in both cultivars. These results indicated that exogenous Spd might improve turfgrass quality and promote the salinity tolerance in the two cultivars of kentucky bluegrass through reducing oxidative damages and increasing enzyme activity both at protein and transcriptional levels. [ABSTRACT FROM AUTHOR]

Four cultivars of Kentucky bluegrass (Poa pratensis L.) are evaluated according to experimental as replicated three times in a randomized block designs at a span of three years. The cultivars of turf quality, colour, leaf width, cover and clipping weight are evaluated during the time of January and December, between the years of 2004 and 2006. According to three years of average values, turf quality scores obtained from Kentucky bluegrass cultivars changes between 7.69 and 7.87, color scores between 6.89 and 7.19, leaf width values between 2.61 and 2.98 mm, turf cover between 91.88 and 95.04 %, clipping weight 312.96 and 361.89 g m-2. It has been concluded that appropriate turfgrass cultivars for the condition of Diyarbakır could be Kentucky bluegrass cultivars are Baron and Geranimo. [ABSTRACT FROM AUTHOR]

Aims: We explored how climate warming and increased atmospheric nitrogen (N) deposition may influence grass litter decomposition over time, how litter quality versus environmental effects contribute to these responses, and the importance of these responses over winter. Methods: We used litter bags to examine decomposition over 2 years in a warming and N addition field experiment, and examined the contributions of litter quality and environment to these responses by transferring litter reciprocally between the treatment plots and a common garden. Results: Warming increased mass loss over the first year for Bromus inermis litter, which was consistent with the litter quality response, but by the second year there was no overall warming effect, and this change coincided with a negative environmental effect of warming. N addition increased mass loss and was more influential than warming in the early stages of Poa pratensis litter decomposition; the N effect appeared to be driven primarily by litter quality. Winter decomposition was not a substantial component of the treatment responses. Conclusions: Our results indicate that litter quality and environmental effects play different roles at different time scales in the decomposition responses of grass litter to warming and N addition, and these responses can be species specific. [ABSTRACT FROM AUTHOR]

Typhula blight is a major problem on golf courses where snow cover persists for long periods. The disease is primarily managed by applying a mixture of fungicides in the autumn prior to winter snow cover. The fungicides chlorothalonil and fludioxonil are often included in these mixtures even though they do not completely suppress Typhula blight when applied alone. We studied whether minimal control was due to a lack of persistence of these fungicides under snow, or whether certain isolates ofTyphula ishikariensisandT. incarnataexhibited tolerance to these fungicides. The persistence of chlorothalonil and fludioxonil residues in the turf was determined during the winters of 2005–06, 2006–07 and 2007–08. Concentrations of chlorothalonil and fludioxonil in the verdure decreased or remained nearly the same at most sampling dates, indicating these fungicides did not dissipate rapidly under snow. Despite this, only marginal control of Typhula blight was observed in the fungicide-treated plots. Thein vitrosensitivity ofT. ishikariensisandT. incarnataisolates to chlorothalonil and fludioxonil was tested. Growth of most isolates (70%) on agar amended with 1 µg mL−1chlorothalonil was inhibited by more than 50% relative to growth on non-amended agar. However, almost all isolates exhibited some growth at concentrations as high as 500 µg mL−1. A high proportion of isolates (85%) were inhibited by greater than 80% at 1 µg mL−1fludioxonil. Therefore, at least some growth of these isolates at high fungicide concentrations may explain why chlorothalonil and fludioxonil are not completely effective in suppressing Typhula blight. [ABSTRACT FROM AUTHOR]

Poa pratensis L. is a forage and turf grass species well adapted to a wide range of mesic to moist habitats. Due to its genome complexity little is known regarding evolution, genome composition and intraspecific phylogenetic relationships of this species. In the present study we investigated the morphological and genetic diversity of 33 P. pratensis accessions from 23 different countries using both nuclear and chloroplast molecular markers as well as flow cytometry of somatic tissues. This with the aim of shedding light on the genetic diversity and phylogenetic relationships of the collection that includes both cultivated and wild materials. Morphological characterization showed that the most relevant traits able to distinguish cultivated from wild forms were spring growth habit and leaf colour. The genome size analysis revealed high variability both within and between accessions in both wild and cultivated materials. The sequence analysis of the trnL-F chloroplast region revealed a low polymorphism level that could be the result of the complex mode of reproduction of this species. In addition, a strong reduction of chloroplast SSR variability was detected in cultivated materials, where only two alleles were conserved out of the four present in wild accessions. Contrarily, at nuclear level, high variability exist in the collection where the analysis of 11 SSR loci allowed the detection of a total of 91 different alleles. A Bayesian analysis performed on nuclear SSR data revealed that studied materials belong to two main clusters. While wild materials are equally represented in both clusters, the domesticated forms are mostly belonging to cluster P2 which is characterized by lower genetic diversity compared to the cluster P1. In the Neighbour Joining tree no clear distinction was found between accessions with the exception of those from China and Mongolia that were clearly separated from all the others. [ABSTRACT FROM AUTHOR]

Measurements were taken of seven morphological characteristics of various forms of Poa pratensis, including ecotypes (12), cultivars (4), and breeding lines (2). Statistically significant differences relating to the average number and length of vegetative shoots and the leaf width of the forms studied were determined using Tukey's HSD test. Evaluation of genetic polymorphism was carried out using the RAPD-PCR method. 18 primers were used for molecular analysis and 473 amplification products were obtained, in which high levels of polymorphism (84.2%) and specificity (63) were discovered. The mean value of Dice's coefficient, the genetic similarity indicator, was about 0.7. These results indicate a significant genetic similarity between most of the forms of Poa pratensis studied. A correlation was also observed between genetic variation and phenotypic diversity of the studied forms of Poa pratensis. Convergence was found to occur between phenotype and genetic similarity among the forms. Only the dos01 468 ecotype showed discrepancies in the assessment of phenotypic and genomic variability. [ABSTRACT FROM AUTHOR]

PGR applications aimed to interfere with gibberellic acid (GA) biosynthesis or accumulation is a widespread practice in the production and maintenance of turfgrasses. If suppression of GA combined with drought stress modifies the content of other hormones in turfgrasses, PGR application could affect the susceptibility of grasses to various abiotic stresses and biotic pathogens. This growth chamber study aimed to investigate how drought stress and Primo (Syngenta Corp; Trinexapac-ethyl; TE) application affect the content of abscisic acid (ABA), auxin (in the form of indole acetic acid, IAA), jasmonic acid (JA), and salicylic acid (SA) in one commercially available cultivar 'Kenblue' and one experimental type, A06-46, of Kentucky bluegrass. Drought stress caused an accumulation of all four of these hormones that began around 8 day of drought stress or at a 20-40 % loss of water from leaves. TE application combined with drought stress caused an earlier increase in SA and IAA content and delayed the increase in JA and ABA content compared to drought-stressed plants not treated with PGR. An increase in SA, JA, and IAA was found at severe water deficit conditions (26 % RWC) in TE-treated plants compared to plants not treated with TE. The results indicate that both negative and positive consequences to plant defense strategies could result from the use of PGRs, which could potentially highly impact recommendations of how to best use PGR compounds in turfgrasses and other crop species. [ABSTRACT FROM AUTHOR]

Plants may survive salinity and alkalinity with differential metabolic responses. The aim of this study was to gain further insights into the differential response to salinity and alkalinity stress at the metabolic level. Two Kentucky bluegrass, 'Midnight' (tolerant) and 'Voyager II' (sensitive), were subjected to salinity (NaCl, 75 mM Na, pH 5.41) and alkalinity (NaCO and NaHCO, 75 mM Na, pH 9.5) in hydroponics. The leaf metabolite profile was determined using gas chromatography-mass spectrometry (GC-MS). Alkaline salts caused more severe damages than neutral salt as indicated by the vertical shoot growth rate (VSGR), turf quality, electrolyte leakage (EL) and lipid peroxidation (MDA content). Adaptation of plants to salinity was mainly associated with the accumulation of amino acids (proline, valine, glutamate, asparagine, glutamine, phenylalanine and lysine) and sugars (sucrose, trehalose). In contrast, the metabolic response to alkalinity stress was mostly associated with the accumulation of organic acids that are mainly sugar acids (gluconate, galactarate, glucarate) and those involved in the citric acid cycle (malate, citrate, isocitrate, succinate, maleiate, aconitate). The differential accumulation of the amino acids, organic acids, sugars and fatty acids may contribute to the differential adaptation strategies due to their roles in the stress response pathways such as osmotic adjustment, membrane stability, respiration for energy production, carbon/nitrogen assimilation, regulation of the intracellular pH and the pH outside roots. [ABSTRACT FROM AUTHOR]

In Isle Royale National Park, heavy moose browsing over the past 100 years has suppressed the regeneration of many tree species, gradually resulting in a shift towards more open forests and savannas. By 1996, 16% of the forests at the southwestern end of Isle Royale had become savanna and another 20% of forests were starting to have canopy breakup. The changes in understory vegetation brought about by savanna formation have received little attention, even though the future of moose and wolf populations on Isle Royale is tied to these vegetation changes. This study examined the vegetation of savannas ranging in age (date since formation) from <10 years to 80 years to examine how the ground flora changes over time from initial forest canopy breakup, to extensive grassland, and finally to a zootic subclimax dubbed 'moose-spruce savanna.' Ordination techniques were used to describe plant communities and to identify environmental variables that influence vegetation development. Nonparametric multiplicative regression was used to predict how these variables influenced individual plants and structure within the communities. Plant communities had a notable shift from forest herbs to ruderal species, especially non-native plants. This succession was influenced strongly by the underlying bedrock and hydrology-altering moisture regimes and plant communities. Picea glauca (Moench) Voss. and Poa pratensis L. competed in a dynamic inhibitory relationship. The former facilitated forest plants while the latter out-competed other plants and promoted open swards. These interactions are dramatically changing the character of Isle Royale's upland plant communities and will have important trophic consequences for the island. [ABSTRACT FROM AUTHOR]

[Display omitted] • Prospective KBG biomass was evaluated for sustainable biofuel production. • HA-assisted alkaline pretreatment delignified KBG biomass up to 70%. • Pretreated biomass was efficiently saccharified to yield 0.55 g/g reducing sugars. • Ethanol yield of 76.6% could be downstream purified and enriched with DCMD. • The new hybrid system enables cellulosic ethanol production at a commercial scale. The effective fractionation of structural components of abundantly available lignocellulosic biomass is essential to unlock its full biorefinery potential. In this study, the feasibility of humic acid on the pretreatment of Kentucky bluegrass biomass in alkaline condition was assessed to separate 70.1% lignin and hydrolyzable biocomponents. The humic acid-assisted delignification followed by enzymatic saccharification yielded 0.55 g/g of reducing sugars from 7.5% (w/v) pretreated biomass loading and 16 FPU/g of cellulase. Yeast fermentation of the biomass hydrolysate produced 76.6% (w/w) ethanol, which was subsequently separated and concentrated using direct contact membrane distillation. The hydrophobic microporous flat-sheet membrane housed in a rectangular-shaped crossflow module and counter-current mode of flow of the feed (hot) and distillate (cold) streams yielded a flux of 11.6 kg EtOH/m2/24 h. A modular, compact, flexible, and eco-friendly membrane-integrated hybrid approach is used for the first time to effectively valorize Kentucky bluegrass biomass for sustainable production of biofuel. [ABSTRACT FROM AUTHOR]

As a commonly used turfgrass, Kentucky bluegrass (Poa pratensis L.) (KBG) has many commercially available cultivars for production. After several years of screening, two new lines were obtained ('KBG03' and 'KBG04'), which have high tolerance to summer. The study showed that the two lines revealed similar morphological characteristics, with light green leaf color, narrow leaf blade, high plant height and light 1,0007grain weight. A total of 400 random amplified polymorphic DNA (RAPD) primers and 256 sequence7related amplified polymorphism (SRAP) primer combinations were screened among the two lines and other 4 imported commercial cultivars. The percentages of polymorphic sites were 65.5% (RAPD) and 22.6% (SRAP) respectively. By cluster analysis of RAPD and SRAP data, the dendrogram at a similarity of 0.29 gave two main clusters, of which one group had 4 commercial cultivars, and the other had the two new breeding lines. Furthermore, one specific band of 'KBG04' was successfully converted into a dominant sequence characterized amplified region marker (SCAR196). Then the SCAR marker was verified by 39 KBG DNA samples, including imported varieties, domestic varieties and self7breeding lines of our laboratory, and it exhibited high consistency with the original RAPD polymorphic amplification. The results showed that the SCAR marker can be used to distinguish the new line 'KBG04' from numerous KBG germplasms, which would be useful for cultivar identification and property rights protection in the future. [ABSTRACT FROM AUTHOR]

Mixtures of turfgrass seed are commonly used to establish lawns, with kentucky bluegrass (KBG) and perennial ryegrass (PRG) comprising two of the more commonly used species. In the humid regions of the Midwest United States, KBG is a desirable species, but slow germination makes it difficult to establish compared with PRG. The objective of our study was to evaluate establishment rate and species composition over 3 years of a turf stand seeded with different ratios of KBG and PRG (wt:wt) maintained as a lawn. Repeat experiments were initiated in 2007 and 2008 and conducted for 3 years in West Lafayette, IN, with seed mixtures of KBG:PRG of 100:0, 90:10, 80:20, 70:30, 50:50, and 0:100 wt:wt of pure live seed. Plots were seeded late August each year and percent turfgrass cover was rated up to 6 weeks after seeding (WAS). To evaluate stand composition after establishment, percent KBG cover was rated annually in August for 3 years using transect counts after selective removal of PRG with the herbicide chlorsulfuron. Likely as a result of greater crabgrass (Digiaria sp.) competition during establishment in 2007, 100% PRG, 50:50, 70:30, or 80:20 KBG:PRG ratio had the highest percentage turf cover at 6 WAS, whereas there was no difference between treatments at 6 WAS in 2008 when crabgrass competition was lower. Regardless of turf cover during establishment, all treatments except 100% PRG shifted to greater than 95% KBG cover by 3 years after establishment. For the region in which our study was conducted, it may be desirable to seed with a higher proportion (greater than 50%) of PRG to speed initial establishment for customer satisfaction, erosion control, and/or to offset years with high weed pressure. Under lawn conditions similar to our study, seeding ratios with high KBG (80:20 or 90:10 KBG:PRG) will likely shift to a stand composition of greater than 95% KBG within 2 years, whereas all other ratios lower in KBG will likely shift similarly within 3 years. Chemical names used: 2-chloro-N-{[(4-methoxy-6-methyl-1,3,5-triazin-2 yl)amino]carbonyl}benzenesulfonamide (chlorsulfuron) [ABSTRACT FROM AUTHOR]

In the Northern Great Plains, invasive grasses Bromus inermis (smooth brome) and Poa pratensis (Kentucky bluegrass) are substantial threats to remnant prairies because they form monotypic stands that decrease diversity and alter nutrient cycling. A greenhouse study was conducted to evaluate the competitive ability of these two invaders and how priority effects influence competition. We grew each invasive species alone, with a conspecific neighbor, and a native neighbor ( Elymus canadensis) to assess competitive ability. Priority treatments included planting both species concurrently, planting the invader prior to the native (by 21 days), and planting the native prior to the invader (by 21 days). Final aboveground biomass and a relative interaction index (RII) were used as response variables to determine the competitive ability of each species. Both competition and priority were found to have a significant effect on native and invasive species performance . Bromus inermis demonstrated a large competitive effect that increased with priority. Poa pratensis demonstrated smaller competitive effects but also benefited from priority. Unexpectedly, our native phytometer E. canadensis demonstrated a very strong competitive effect that, when coupled with priority, nearly excluded one of the invasive species. [ABSTRACT FROM AUTHOR]

Temperate grasslands worldwide have been reduced to remnants as a result of urban, rural, and oil and gas activities. One of the largest remaining tracts of temperate grassland is located in central Alberta, Canada: a provincial protected natural area known as Rumsey Block. Although Rumsey Block has been protected from urban and rural development, oil and gas activities have been allowed. We analyzed the change in plant communities from several oil and gas disturbances over an eleven-year period. We developed a state and transition model displaying consequences of disturbances from grazing and oil and gas development on rough fescue grassland, considered the reference stable state. Transitions were no, light, or moderate grazing and minimum oil and gas disturbance, such as plow-in pipelines, small area well sites (<25 m2) and sites seeded with native species or left to natural recovery. Triggers, causing change from rough fescue grassland to altered states, were heavy grazing, and moderate to major oil and gas disturbances, such as topsoil stripping and seeding with introduced species. Within the reference state, three plant communities were identified, varying from rough fescue ( Festuca hallii) grassland to grazing-induced variations where shortbristle needle and thread ( Hesperostipa curtiseta) became dominant. Two altered states were identified: Introduced Grasses and Native Grasses. All altered states were deemed to have crossed a threshold requiring complete eradication of species and reseeding. Based on these results, we recommend minimum disturbance in grasslands, such as light grazing, plow-in pipelines, small areas well sites, and natural recovery. [ABSTRACT FROM AUTHOR]

Phytoliths in Poa pratensis L. (Poaceae) leaf blades and sheaths are described in this study. The role of plant opal particles--known as phytoliths--is considerable in taxonomical studies, and their long-term preservation in sediments makes them a useful tool in the reconstruction of ancient plant communities and plant-human interactions. All together, 2244 phytoliths were counted and analyzed in 25 plant samples (5 shoots of 5 specimens and approximately 500-600 phytoliths per specimen). The biogenic silica content of P. pratensis leaves was determined at 2.61%, and 27 morphotypes have been described using the International Code for Phytolith Nomenclature. Two morphotypes are described for the first time in this study. Long cells (elongate psilate and sinuate morphotypes) and short cells (rondel-trapeziform elongated and rounded morphotypes) are frequently present in this species. Differences in morphotype frequency and significant differences in a few simple morphometric data (length, width, height) of long cells and short cells were found among specimens, which suggests that these features vary depending on environmental factors and the maturity of leaf tissues. [ABSTRACT FROM AUTHOR]

Aims Invasive plants commonly occupy disturbed soils, thereby providing a stage for understanding the role of disturbance-enhanced resources in plant invasions. Here, we addressed how soil space and soil nutrients affect the growth and competitive effect of invasive plants and whether this effect varies with different invaders. Methods We conducted an experiment in which two invasive plants (Bromus tectorum and Centaurea maculosa) and one native species (Poa pratensis) were grown alone or together in four habitats consisting of two levels of soil space and nutrients. At the end of the experiment, we determined the total biomass, biomass allocation and relative interaction intensity of B. tectorum, C. maculosa and P. pratensis. Important Findings Across two invaders, B. tectorum and C. maculosa, increased soil nutrients had greater positive effects on their growth than increased soil space, the effects of soil space on root weight ratio were greater than those of soil nutrients, and their competitive effect decreased with soil space but increased with soil nutrients. These findings suggest that changing soil space and nutrients differentially influence the growth and competitive advantages of two invaders. Bromus tectorum benefited more from increased soil resources than C. maculosa. Soil space and nutrients affected the biomass allocation of C. maculosa but not B. tectorum. The competitive effect of B. tectorum was unaffected by soil space and soil nutrients, but the opposite was the case for C. maculosa. Thus, the effects of soil space and nutrients on growth and competitive ability depend on invasive species identity. [ABSTRACT FROM AUTHOR]

Few correlation or calibration studies have been conducted to determine or validate sufficiency levels of N concentrations in the clippings of turfgrass for color and growth responses. In a series of field experiments conducted across six consecutive growing seasons (2007-2012) in Connecticut, clipping samples of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns were used to estimate yields and then analyzed for N concentrations. Chlorophyll and normalized difference vegetative index (NDVI) meters were used to quantify turf color before sampling. Macy's concept of three nutritional zones of plant tissue nutrient concentration was used to identify minimum and critical concentrations of N in the clippings that define sufficiency ranges for color and growth responses, in addition to luxury consumption. Averaged across all variables and seasons (spring, summer, and fall), the sufficiency ranges of N concentration in the clippings were estimated to be 32 to 46 g kg-1 for Kentucky bluegrass, and 28 to 42 g kg-1 for tall fescue. Differences in minimum and critical concentrations among seasons and between species were thought to be due to demanddriven nutrient uptake. Luxury consumption of N was observed in both species. When used in context with local conditions, tissue analysis for N concentrations in cool-season turfgrass clippings can provide an objective basis for guiding N fertilization. [ABSTRACT FROM AUTHOR]

Under climate change, alterations to precipitation and temperature regimes are expected to impact ecosystem structure and function. These impacts may in part be determined by feedbacks between plants and associated microbes, including both endophytic fungal symbionts and viral pathogens., To test potential key components of these feedbacks in a grassland system, we conducted a field experiment that factorially manipulated temperature regime, precipitation regime and endophyte infection of a dominant species, Schedonorus arundinaceus. After one growing season, we evaluated the four most frequently occurring grass species for infection by three species of barley and cereal yellow dwarf viruses (B/ CYDVs). For S. arundinaceus, we also tracked changes in viral prevalence over an additional two growing seasons, for a total of three growing seasons., Plant species identity played a strong role in determining virus prevalence; Poa pratensis and Paspalum dilatatum were more frequently infected than either S. arundinaceus (endophyte infected or endophyte free) or Eleusine indica. Both elevated temperature and elevated precipitation impacted virus prevalence, but effects varied among years and interacted with fungal endophyte symbiosis for S. arundinaceus., In the final year of data collection, elevated precipitation increased virus prevalence in endophyte-infected, but not endophyte-free, S. arundinaceus. In the same year, but regardless of endophyte infection, elevated temperature by itself increased virus prevalence for S. arundinaceus. This effect of temperature on virus prevalence may have been driven by vector abundance because the viruses are obligately aphid-transmitted, and aphids were found more frequently in heated plots., Synthesis. Overall, our investigation experimentally demonstrates strong combined impacts of biotic and abiotic factors on disease dynamics in a grassland system. Impacts of climate change on virus prevalence in grasslands may depend on the responses of aphid vectors and the presence of endophytic fungal symbionts. [ABSTRACT FROM AUTHOR]

Mixtures of turfgrass species are commonly used throughout the world when establishing cool-season grasses from seed. However, there have been limited studies investigating how various species compete with each other as the turf matures. A study was conducted in Padova, Italy, to investigate the performance and species composition of four mixtures that contained a single cultivar of Kentucky bluegrass (KB; Poa pratensis L.) and two rhizomatous or two nonrhizomatous tall fescue (TF; Festuca arundinacea Schreb.) cultivars. The trial was seeded in September 2010. Three mowing heights (20, 32, and 62 mm) were also applied to all the mixtures. General turfgrass performance of the mixtures was monitored through the 2011 growing season, and species composition was measured regularly to determine the abundance of both species in the mixture. Throughout the study, the mixtures containing the rhizomatous TF consistently had higher turfgrass quality and turfgrass density than mixtures containing the nonrhizomatous types. Mowing height had less effect on the performance of the mixtures, but the lower mowing heights (20 and 32 mm) performed more consistently than the plots mowed at the highest (62 mm) mowing height. Species composition of the mixtures was significantly influenced by the different TF cultivars, in that KB was less abundant in mixtures containing rhizomatous TF cultivars compared to nonrhizomatous cultivars, suggesting an increased competitive ability of rhizomatous TF lines. Mowing height also influenced the species composition, in that KB was significantly more abundant at lower mowing heights. [ABSTRACT FROM AUTHOR]

In addition to typical meadow species, Poa pratensis, 4 other species are recognized within this aggregate. Only the leaf width is used often for their identification. These species are known to be satisfactorily distinguished in their growth habits, but detailed studies showed that growth habit is not a reliable discriminator and it seems to be only a reflection of general trends. Neither width of leaves, nor characters of growth habit are successful features in their identification. To avoid wrong identifications, which could lead undesirable consequences, all morphological characters and growth habit should be simultaneously taken into consideration. [ABSTRACT FROM AUTHOR]

This experiment was carried out in laboratory conditions. The aim of this work was estimating allelopathic potential of Taraxacum officinale on seeds germination and initial growth of Poa pratensis. In the experiment different concentration of soil's and plant's water solution obtained from common dandelion were employed. The inhibition of germination energy of Poa pratensis under the influence of plant extracts produced from roots and leaves of Taraxacum officinale was found. Germination availability was inhibited in a higher degree by extracts prepared from the leaves than the roots of Taraxacum officinale. Higher concentrations of all solutions of both the soil and the plant inhibited the length of seending of Poa pratensis. [ABSTRACT FROM AUTHOR]

Elevated CO2 concentration may promote plant growth while high temperature is inhibitory for C3 plant species. The interactive effects of elevated CO2 and high temperatures on C3 perennial grass growth and carbon metabolism are not well documented. Kentucky bluegrass (Poa pratensis) plants were exposed to two CO2 levels (400 and 800 μmol mol−1) and five temperatures (15/12, 20/17, 25/22, 30/27, 35/32°C, day/night) in growth chambers. Increasing temperatures to 25°C and above inhibited leaf photosynthetic rate (Pn) and shoot and root growth, but increased leaf respiration rate (R), leading to a negative carbon balance and a decline in soluble sugar content under ambient CO2. Elevated CO2 did not cause shift of optimal temperatures in Kentucky bluegrass, but promoted Pn, shoot and root growth under all levels of temperature (15, 20, 25, 30, and 35°C) and mitigated the adverse effects of severe high temperatures (30 and 35°C). Elevated CO2-mitigation of adverse effects of high temperatures on Kentucky bluegrass growth could be associated with the maintenance of a positive carbon balance and the accumulation of soluble sugars and total nonstructural carbohydrates through stimulation of Pn and suppression of R and respiratory organic acid metabolism. [ABSTRACT FROM AUTHOR]

The use of sod to establish turf on sand-based root zones often leads to layering of contrasting soil textures within the root zone, causing adverse effects on soil drainage and moisture. These issues may be alleviated by alternative establishment methods and post-establishment cultural practices. Objectives of this study were to test the effects of sod establishment method, aerification, and sand topdressing on water infiltration, soil moisture, root mass, and divot resistance of Kentucky bluegrass (Poa pratensis L.) on sand-capped and native soil root zones. In 2010, cultivar Midnight Kentucky bluegrass was established in Fayetteville, AR, using standard (soil-based), washed, and pre-harvest, core-aerified sod on a sand-capped and a native silt loam root zone. After establishment, core aerification treatments (non-cultivated vs. 20% surface area affected annually) and topdressing treatments (0.6-cm sand applied one vs. four times yr-1) were imposed. The washed sod resulted in lower volumetric water content (VWC) (-3 to 4%) for both the root zones in 2010 and only for the sand-capped system in 2011. Core-aerification improved water infiltration rate (13% increase) and reduced the VWC (-44% at end of study) of the sand-capped root zone. The effects ofcultural practices on root mass density and divot resistance were oflimited practical importance. Core-aerification and topdressing appeared effective for managing layered root zones and would likely improve the long-term quality of golf and sports turfs. [ABSTRACT FROM AUTHOR]

Turfgrass species differ greatly in their ability to withstand the abrasion and compaction of traffic. Wear tolerance of turfgrass species and cultivars has been evaluated abroad by many researchers, while only few and partial studies have been conducted in Italy. Field experiment was carried out in Viterbo in 2001, 2002 and 2003 to evaluate the effect of the simulated traffic on 110 varieties belonging to four turfgrass cool-season species: tall fescue (Festuca arundinacea Schreb.), fine fescues (Festuca rubra L. ssp. rubra Gaud., ssp. commutata Gaud., ssp. tricophylla Gaud.), perennial ryegrass (Lolium perenne L.) and Kentucky bluegrass (Poa pratensis L.). Shoot density, visual turfgrass quality and thatch thickness were the major characters recorded to estimate wear tolerance. Traffic was simulated using a device containing three rollers pulled by a small tractor. The traffic simulator weighed 564 kg and applied a pressure of about 3 MPa. Results indicated that perennial ryegrass and tall fescue had high wear tolerance and low statistical variation among cultivars. Kentucky bluegrass showed an average wear tolerance owing to its shoot density and good recovery potential. In spite of their high shoot density, fine fescues exhibited poor wear tolerance because of their scarce resistance to high temperatures which are typical of the Mediterranean climate in late spring and summer. This study enabled a preliminary selection of the most suitable cool-season grasses and cultivars for trafficked and non-trafficked areas in Central Italy and highlighted that different turfgrass species have different wear tolerance mechanisms.