Poa Compressa Research Articles

Feasibility of Using Phytoextraction to Remediate a Compost-Based Soil Contaminated with Cadmium

Greenhouse and in-situ field experiments were used to determine the potential for phytoextraction to remediate soil contaminated with Cd from municipal solid waste (MSW) and sewage sludge (SS) compost application at a Peterborough (Canada) site. For the greenhouse experiment, one native (Chenopodium album) and three naturalized (Poa compressa, Brassica juncea, Helianthus annuus) plant species were planted in soil containing no detectable Cd (<1.0 μg·g−1), and soil from the site containing low (5.0 ± 0.3 μg·g−1 Cd), and high (16.5 ± 1.2 μg⋅g−1 Cd) Cd concentrations. Plant uptake was low (root BAFs ≤0.5) for all species except P. compressa in the low Cd treatment (BAF 1.0). Only B. juncea accumulated Cd in its shoots, though uptake was low (BAF ≤0.3). For the field experiment, B. juncea was planted in-situ in areas of low and high Cd concentrations. Brassica juncea Cd uptake was low (root and shoot BAFs <0.2) in both treatments. Sequential extraction analysis indicated that Cd is retained primarily by low bioavailability soil fractions, and phytoextraction is therefore not feasible at this site. Though low Cd bioavailability has negative implications for Cd phytoextraction from MSW/SS compost-based soils, it may limit receptor exposure to Cd sufficiently to eliminate the potential for risk at this site.

Потенциальные возможности распространения адвентивного растения Poa compressa L. в Сибири

Потенциальные возможности распространения адвентивного растения Poa compressa L. в Сибири

Mycorrhizal status of plants in two successional stages on spoil heaps from fireloam mining in Lower Silesia (SW Poland)

The mycorrhizal status of two plant communities representing an initial stage (1-2 year-old) and a 8-9-year-old stage of succession on spoil heaps from fireloam mining in Lower Silesia, Poland, was determined. In the initial stage, the mycorrhizal structures were not observed in 39% of the investigated species; they were members of the &lt;em&gt;Polygonaceae&lt;/em&gt;, &lt;em&gt;Chenopodiaceae&lt;/em&gt; and &lt;em&gt;Poaceae&lt;/em&gt; families. The relative cover of non-mycorrhizal plants exceeded 50% and the major role was played by the &lt;em&gt;Polygonum aviculare&lt;/em&gt; population, which predominated the whole community. Mycorrhizal species (arbuscular mycorrhizae) contributed to 61 % of the composition of the initial phyto-coenosis. The most numerous taxa were those with 20-40% of the root length colonized, with a small number of arbuscules (0.2-3.1% of the root length containig arbuscules) and no vesicles. In the advanced stage of succession, mycorrhizal plants definitely dominated and the major role was played by the &lt;em&gt;Tussilago farfara&lt;/em&gt; population. Compared with the initial stage, the later one also harboured more plants with mycorrhizas occupied &amp;gt;40% of the root length, as well as containing numerous arbuscules (&amp;gt;20% of the root length) and vesicles. The non-mycorrhizal species, i.e., &lt;em&gt;Equisetum arvense&lt;/em&gt; and &lt;em&gt;Poa compressa&lt;/em&gt;, represented 11 % o': the community composition and their relative cover amounted to 3%. Despite the relatively frequent occurrence of the arbuscular mycorrhizae in the initial stage of succession, the qualitative properties of the colonization indicated a low effectiveness of symbiosis. This could be caused by the lack of adaptation of the fungal symbiont to the edaphic conditions which were changed after disturbance.

Arbuscular mycorrhizas in phosphate-polluted soil: interrelations between root colonization and nitrogen

To investigate whether arbuscular mycorrhizal fungi (AMF) – abundant in a phosphate-polluted but nitrogen-poor field site – improve plant N nutrition, we carried out a two-factorial experiment, including N fertilization and fungicide treatment. Percentage of root length colonized (% RLC) by AMF and tissue element concentrations were determined for four resident plant species. Furthermore, soil nutrient levels and N effects on aboveground biomass of individual species were measured. Nitrogen fertilization lowered % RLC by AMF of Artemisia vulgaris L., Picris hieracioides L. and Poa compressa L., but not of Bromus japonicus Thunb. This – together with positive N addition effects on N status, N:P-ratio and aboveground biomass of most species – suggested that plants are mycorrhizal because of N deficiency. Fungicide treatment, which reduced % RLC in all species, resulted in lower N concentrations in A. vulgaris and P. hieracioides, a higher N concentration in P. compressa, and did not consistently affect N status of B. japonicus. Evidently, AMF had an influence on the N nutrition of plants in this P-rich soil; however – potentially due to differences in their mycorrhizal responsiveness – not all species seemed to benefit from a mycorrhiza-mediated N uptake and accordingly, N distribution.

Restoration of foothills rough fescue grassland following pipeline disturbance in southwestern Alberta

The effects of pipeline construction and reclamation techniques on the restoration of rough fescue plant communities following pipeline construction in southwestern Alberta, Canada were evaluated after 7–40 years. The pipeline construction right-of-way (ROW) sites varied from no recovery of rough fescue grassland to moderate recovery. The ROW sites had a higher proportion of introduced grasses and forbs, less topsoil, and poorer rangeland health than the adjacent undisturbed grassland. Within the ROW sites, less topsoil was present on those with larger diameter pipe and which had topsoil fully stripped from the ROW during construction. Introduced grasses, Festuca ovina (sheep fescue) and Poa compressa (Canada bluegrass), succeeded in establishment following seeding and persisted for at least 40 years. Poa pratensis (Kentucky bluegrass) dominated many of the ROW sites. Contributing factors to moderate recovery of rough fescue grassland were related to post-growing season pipeline construction, ideally, between August and March, summer or fall seeding, and minimum disturbance trench-only stripping. Reclamation practices appeared more important than time since restoration in the restoration of rough fescue grassland.

Population dynamics of greenbug biotypes “E” and “F” on Texas bluegrass

AbstractCool‐season perennial forage grasses are known to serve as alternate hosts of the greenbug, Schizaphis graminum (Rondani) in the southern Great Plains of the USA. Texas bluegrass (Poa arachnifera Torr.) is a cool‐season perennial forage grass indigenous to this region and because of its persistence under grazing is being bred for improved forage production. An experiment was conducted to determine the population dynamics of greenbug biotype “E”, the predominant biotype found in this region and biotype “F” which is known to infest bluegrass species. Twenty‐five Texas bluegrass genotypes, three Kentucky bluegrass (Poa pratensis L.) genotypes, a Canada bluegrass (Poa compressa L.) genotype, two Texas × Kentucky bluegrass hybrids, and a Texas × Canada bluegrass hybrid were screened for their abilities to support greenbug population growth. Bluegrass species and genotypes varied significantly in their ability to support greenbug biotypes E and F. On the basis of higher aphid numbers, biotype E had a higher population growth rate as compared with biotype F on Texas bluegrass. Some Texas bluegrass genotypes were not included in both biotype trials due to lack of availability of uniform plant material for inoculation. Nine of 25 Texas bluegrass genotypes did not support biotype E greenbug population growth. Similarly, 13 of 22 Texas bluegrass genotypes did not support biotype F population growth. Both Canada and Kentucky bluegrass supported high populations of biotype F and interspecific hybrids varied in their host suitability to both biotypes.

Water uptake in green roof microcosms: Effects of plant species and water availability

Green roofs are engineered ecosystems that rely on vegetation to provide services such as reduction of roof temperatures. Drought resistance is critical for plant survival on shallow-substrate green roofs, but potential trade-offs exist between water-use efficiency and ecosystem functions like transpirative cooling. Water loss from simulated green roof systems (microcosms) each containing 1 of 14 plant species belonging to 4 growth forms (succulents, herbaceous dicots, grasses and woody creeping shrubs) was quantified for 3 watering treatments (watering to field capacity every 4, 11 and 24 days). After 2 months only succulents survived the dry treatment. The dry treatment was the only treatment in which planted microcosms showed consistently greater water loss (∼30% greater) than the controls (soil-only microcosms). Microcosms planted with Poa compressa lost the most water in all moisture treatments but in the wet and intermediate treatments, respectively, native species Rhodiola rosea and Campanula rotundifolia had equivalent performance to P. compressa. The mat-forming Sedum acre retained more water than controls and other species in the wet and intermediate treatments suggesting that its growth form impeded evaporation from the soil surface. Performance differences among growth forms and species across soil moisture gradients suggest that optimal water loss and roof surface cooling could be enhanced by planting multiple species.

Exotic plant species in the southern boreal forest of Saskatchewan

Exotic species possess abilities to harm the ecosystems they invade. This study assesses the density, frequency and cover of exotic plants in roadside right-of-ways, logged areas and wildfire sites within mixedwood sections of the southern boreal forest of Saskatchewan. A total of 23 exotic species were observed including nine species of Gramineae, seven species of Leguminosae and five species of Compositae. Average density of exotic species in areas recently disturbed by timber harvesting or wildfire was 0.2 stems m −2 with a frequency of 72%. Exotic species adapted for wind dispersal were best represented including common dandelion ( Taraxacum officinale), perennial sow thistle ( Sonchus arvensis) and annual hawksbeard ( Crepis tectorum). Only two exotic species, T. officinale and Canada bluegrass ( Poa compressa), were observed in mature forest; both occurred with a frequency of 13% and an average density of 0.002 stems m −2. A total of 22 exotic species was found in the right-of-ways quadrats with an average density of 117 stems m −2 and a frequency of 94%. The most frequently observed exotic species in the roadside right-of-way areas were T. officinale, alsike clover ( Trifolium hybridum), S. arvensis, creeping red fescue ( Festuca rubra) and smooth brome grass ( Bromus inermis). These species are either common agricultural weeds or were part of the original seed mixture used to establish a plant cover in the roadside right-of-ways. Each of the exotic species observed was ranked to determine its current and potential threat to ecosystem attributes. The majority were considered a lesser threat and easy to control, with eight species ranked as a lesser threat and hard to control, and one species, B. inermis, ranked as a serious threat and hard to control. The distribution of exotic species was closely related to the management of roadside right-of-ways, wildfire events and timber harvesting. An increased distribution of exotic species was observed within roadside right-of-ways areas which had been subjected to more intensive management. Although the exotic species observed in this study are maintained and dispersed by management activities, the majority of exotic species are not a threat to this forest ecosystem in the southern boreal forest of Saskatchewan.

(51) Intermountain West Native and Adapted Grass Species and Their Management for Turfgrass Applications

The ongoing drought in the Intermountain West has brought a great deal of attention to water conservation over the past several years. During that time, turfgrass irrigation has been targeted as a source for large potential water savings. Some communities promote downsizing turfgrass areas as the best water conservation measure. In reality, turfgrass controls erosion, reduces evaporation from a site, and provides a safe surface for human activities. One alternative to elimination would be wider use of low water-use-grasses appropriate to the area. However, many questions arise regarding the choice of such grasses and their management. Our research addresses these questions. Plots have been established at Montana State University, Bozeman; Utah State University, Logan; and USDA-NRCS Plant Materials Center, Bridger, Mo. The grasses considered include 12 single species and 12 mixed species stands of `Cody' buffalograss, `Foothills' Canada bluegrass, `Bad River' blue grama, sheep fescue, sandberg bluegrass, muttongrass, and wheatgrasses `Sodar' streambank, `Road Crest' crested, `Rosana' western, and `Critana' thickspike with Kentucky bluegrass and tall fescue as controls. Line source irrigation allowed the plots to be evaluated at a number of levels of irrigation. Experimental measurements on the plots included growth response as determined by clipping yield and quality ratings, and species composition. Fescues and wheatgrasses retained their color, texture, and density throughout the growing season, regardless of moisture level. Warm-season grasses performed well in June, July, and August only, and worked poorly in mixtures as the green cool-season grasses could not mask the brown dormant leaves in cooler weather.

Establishment and Growth of Experimental Grass Species Mixtures on Coal Mine Sites Reclaimed with Municipal Biosolids

The Surface Mining Control and Reclamation Act of 1977 requires that coal mine sites in the United States be reclaimed to establish vegetative cover that is diverse, native, and capable of plant succession. However, there is a question as to whether vegetation established on coal mine sites reclaimed with biosolids is diverse and capable of plant succession. The influx of nutrients with the addition of biosolids leads to long-term dominance by early-successional species, most notably grasses, and consequently, a low establishment of woody and volunteer species. Additionally, many grass species commonly planted in reclamation have aggressive growth habits that lead to their dominance in coal mine plant communities. The establishment and growth of selected grass mixes was evaluated to determine whether alternative grass mixes would be less competitive with woody and volunteer species as compared to commonly used grass mixes. Percent vegetative cover, species richness, and the survival of direct-seeded woody species were assessed for each treatment grass mixture. It was found that Poa compressa and a mixture of P. compressa, Panicum virgatum, and Trifolium repens provided adequate coverage while still allowing the highest species richness and survival of woody species. Use of these species mixtures in coal mine reclamation with biosolids in the eastern United States would likely lead to establishment of a more species-rich plant community with a greater woody species component while still providing erosion control and site protection.

Кальцефитные степные сообщества бассейна реки Сейм (в пределах Курской области)

The paper deals with the calciphyte steppe com­munities of the Seim River basin (Kursk Region), represented by the two new associations, Asperulo cynanchicae—Onobrychidietum arenariae ass. nov. and Achilleo collinae—Astragaletum onobrychis ass. nov., which form a new suballiance Bupleuro falcati—Gyp­sophi­lenion altissimae suball. nov. The diagnostic spe­cies of this unit are Anthemis tinctoria, Bupleurum falcatum, Campanula sibirica, Centaurea pseudomacu­­losa, Gypso­phila altissima, Jurinea arachnoidea, Poa compressa, Polygala sibirica, Salvia stepposa, S. ver­­ticillata, Viola rupestris and the ass. Asperulo-Ono­brychidietum is selected as its holotype. The suballiance comprises calciphyte steppe communities on Cre­ta­ceous marl outcrops in both steep and gentle southern and south-eastern gully slopes, characterized by the combination of calciphyte petrophytes and typical steppe plants. According to the diagnostic species set, the unit is referred to the alliance Festucion valesiacae Klika 1931. The studied communities may be treated as a variant of the petrophytic calciphyte steppes distributed in the south-western part of the Middle-Russian Upland.

Root growth and metal uptake in four grasses grown on zinc-contaminated soils.

Depth and area of rooting are important to long-term survival of plants on metal-contaminated, steep-slope soils. We evaluated shoot and root growth and metal uptake of four cool-season grasses grown on a high-Zn soil in a greenhouse. A mixture of biosolids, fly ash, and burnt lime was placed either directly over a Zn-contaminated soil or over a clean, fine-grained topsoil and then the Zn-contaminated soil; the control was the clean topsoil. The grasses were 'Reliant' hard fescue (Festuca brevipila R. Tracey), 'Oahe' intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia], 'Ruebens' Canada bluegrass (Poa compressa L.), and 'K-31' tall fescue (Festuca arundinacea Schreb.). Root growth in the clean soil and biosolids corresponded to the characteristic rooting ability of each species, while rooting into the Zn-contaminated soil was related to the species' tolerance to Zn. While wheatgrass and tall fescue had the strongest root growth in the surface layers (0-5 cm) of clean soil or biosolids, wheatgrass roots were at least two times more dense than those of the other grasses in the second layer (5-27 cm) of Zn-contaminated soil. When grown over Zn-contaminated soil in the second layer, hard fescue (with 422 mg/kg Zn) was the only species not to have phytotoxic levels of Zn in shoots; tall fescue had the highest Zn uptake (1553 mg/kg). Thus, the best long-term survivors in high-Zn soils should be wheatgrass, due to its ability to root deeply into Zn-contaminated soils, and hard fescue, with its ability to effectively exclude toxic Zn uptake.

Root Growth and Metal Uptake in Four Grasses Grown on Zinc-Contaminated Soils

Depth and area of rooting are important to long-term survival of plants on metal-contaminated, steep-slope soils. We evaluated shoot and root growth and metal uptake of four cool-season grasses grown on a high-Zn soil in a greenhouse. A mixture of biosolids, fly ash, and burnt lime was placed either directly over a Zn-contaminated soil or over a clean, fine-grained topsoil and then the Zn-contaminated soil; the control was the clean topsoil. The grasses were ‘Reliant’ hard fescue (Festuca brevipila R. Tracey), ‘Oahe’ intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia], ‘Ruebens’ Canada bluegrass (Poa compressa L.), and ‘K-31’ tall fescue (Festuca arundinacea Schreb.). Root growth in the clean soil and biosolids corresponded to the characteristic rooting ability of each species, while rooting into the Zn-contaminated soil was related to the species' tolerance to Zn. While wheatgrass and tall fescue had the strongest root growth in the surface layers (0–5 cm) of clean soil or biosolids, wheatgrass roots were at least two times more dense than those of the other grasses in the second layer (5–27 cm) of Zn-contaminated soil. When grown over Zn-contaminated soil in the second layer, hard fescue (with 422 mg/kg Zn) was the only species not to have phytotoxic levels of Zn in shoots; tall fescue had the highest Zn uptake (1553 mg/kg). Thus, the best long-term survivors in high-Zn soils should be wheatgrass, due to its ability to root deeply into Zn-contaminated soils, and hard fescue, with its ability to effectively exclude toxic Zn uptake.

Turfgrass Evaluation of Native Grasses for the Northern Great Plains Region

ABSTRACTA range of native grass species evolved under the environmental extremes of a continental climate in the northern Great Plains, but most have not been evaluated for their suitability as turf. The objective of this research was to evaluate the turfgrass potential of a range of native grasses under three mowing heights. Twelve species (a total of 28 entries) were evaluated under three mowing heights (62, 38, and 18 mm), for turf quality, color, and density at two locations in Manitoba, Canada. The species evaluated included alpine bluegrass (Poa alpina L.), alkali grass [Puccinellia nuttalliana (Schult.) Hitchc.], alpine fescue [Festuca ovina L. var. brachyphylla (Schult. &amp; Schult. f.) Piper, syn. F. brachyphylla Schult. &amp; Schult. f.], blue grama [Bouteloua gracilis (Kunth) Lag. ex Griffiths], buffalograss {Buchloe dactyloides (Nutt.) Engelm. [= Bouteloua dactyloides (Nutt.) Columbus]} Canada bluegrass (Poa compressa L.), fescue spp., fowl bluegrass (Poa palustris L.), Idaho bentgrass (Agrostis idahoensis Nash), marsh muhly [Muhlenbergia racemosa (Michx.) Britton et al.], prairie junegrass [Koeleria macrantha (Ledeb.) Schult.], rough hairgrass {Agrostis scabra Willd. [= A. hyemalis var. scabra (Willd.) H. L. Blomq.]}, side‐oats grama [Bouteloua curtipendula (Michx.) Torr.], and tufted hairgrass [Deschampsia cespitosa (L.) P. Beauv.]. Entries showed similar results across all mowing heights. ‘Bad River’ blue grama, Minnesota ecotype blue grama, and ‘Barkoel’ prairie junegrass entries showed high quality ratings across all years and locations. Blue grama, a warm‐season grass, was drought tolerant and maintained consistent green color throughout the growing season. Although a number of the species showed promise, most entries will require a breeding and selection program before release as low‐maintenance turfgrasses.

Ethylene emission and responsiveness to applied ethylene vary among Poa species that inherently differ in leaf elongation rates.

A plant's ability to produce and respond to ethylene is essential for its vegetative growth. We studied whole-shoot ethylene emission and leaf growth responses to applied ethylene in four Poa spp. that differ inherently in leaf elongation rate and whole-plant relative growth rate. Compared with the fast-growing Poa annua and Poa trivialis, the shoots of the slow-growing species Poa alpina and Poa compressa emitted daily 30% to 50% less ethylene, and their leaf elongation rate was more strongly inhibited when ethylene concentration was increased up to 1 microL L(-1). To our surprise, however, low ethylene concentrations (0.02-0.03 microL L(-1)) promoted leaf growth in the two slow-growing species; at the same concentrations, leaf elongation rate of the two fast-growing species was only slightly inhibited. All responses were observed within 20 min after ethylene applications. Although ethylene generally inhibits growth, our results show that in some species, it may actually stimulate growth. Moreover, in the two slow-growing Poa spp., both growth stimulation and inhibition occurred in a narrow ethylene concentration range, and this effect was associated with a much lower ethylene emission. These findings suggest that the regulation of ethylene production rates and perception of the gas may be more crucial during leaf expansion of these species under non-stressful conditions and that endogenous ethylene concentrations are not large enough to saturate leaf growth responses. In the two fast-growing species, a comparatively higher ethylene endogenous concentration may conversely be present and sufficiently high to saturate leaf elongation responses, invariably leading to growth inhibition.

Nonequilibrium dynamics of sedge meadows grazed by cattle in southern Wisconsin

Equilibrium theory predicts that after disturbance, ecosystemseventually regain the structural and functional properties characteristic oftheir predisturbance condition. This study tested this idea by examining theeffects of cattle grazing and exclusion on the long-term structuralcharacteristics of sedge meadows in southern Wisconsin. To compare structuralchanges in mean percentage cover and height, repeated measures analysis wasconducted on two sedge meadows over a twenty year period from 1977 to 1997. Onesedge meadow was recovering from cattle grazing (cattle excluded in 1973) andthe other was a reference area (nearly undisturbed). Both of these study siteschanged structurally from 1977 to 1997, supporting non-equilibrium theory.Additional observations were made in a heavily and lightly grazed sedge meadowthat were surveyed in 1977. As based on the positions of subunits in anordination graph produced using Non-Metric Multidimensional Scaling (NMS), therecovery sedge meadow became less structurally similar to the grazed and moresimilar to the reference site over the 20 year study. However, from theperspective of mean maximum height in another NMS analysis, the recovery sedgemeadow became less similar to the reference site over time likely because by1997, a shrub carr of Cornus sericea had developed in therecovery sedge meadow that had been dominated by graminoids and forbs in 1977(mean maximum height: 1977 vs. 1997; 0 vs. 47 cm). Seedlings ofCornus sericea were invading the grazed sedge meadows andin the recovery sedge meadow (cattle excluded 4 years earlier) in 1977. A shrubcarr did not develop in the reference sedge meadow. Changes in the referencesite were relatively minor over this time interval; certain species eitherincreased or decreased in dominance, e.g., Carex strictaincreased in cover (1977 vs. 1997, 20 and 28 mean percentage (%) cover,respectively). A few short-term species of the recovery sedge meadow followedthe tenets of equilibrium theory. These became less common or disappeared4–9 years after cattle exclusion including Asterlanceolatus, Calamagrostis canadensis,Poa compressa, Solidago altissima andVerbena hastata. Some of these species were eaten andlikely spread by the cattle. This study suggests that the progression of sedgemeadow to shrub carr may not be an inevitable outcome of succession but insteadcan be a consequence of past cattle grazing history. Also, because the recoveryand the reference sedge both changed structurally over time, the tenets ofnon-equilibrium theory were supported by this study.

TESTING NATIVE GRASSES FOR SURVIVAL AND GROWTH IN LOW pH MINE OVERBURDEN

Overburden piles at the Molycorp molybdenum mine in north central New Mexico contain neutral rock types as well as mixed volcanic rocks, which are highly weathered materials with low pH and high salinity from pyrite oxidation. The mixing of rock types during overburden pile construction has resulted in heterogeneous substrates with a range of pH and soluble salt levels. An experiment to determine grass species more likely to survive and grow in these low pH overburden materials used substrate treatments consisting of an unadulterated acid rock, an acid:neutral overburden mixture ratio of 9: I, and an acid:neutral overburden mixture ratio of 3:1. Containerized grass seedlings of 54 species/ecotypes, primarily cool-season natives of the western U.S, were transplanted into these substrates. Species grown from seed collected at the Mo\ycorp site having superior performance included Muhlenbergia montana (2 ecotypes), Blepharoneuron trieholepis, Festuea species (3 ecotypes), and a Poa species. A number of commercially available grass varieties had good survival and growth in these substrates: Deschampsia caespitosa 'Peru Creek Festuea ari:::onica 'Redondo', Festuca ovina 'Covar Festuea ovina 'MX-86', Festllea sp. 'Shorty', Poa compressa 'Reubens', Paseopyrum smith;; 'Arriba, Barton, and Rosana and Elymus traehycaulus 'San Luis'. Other native grass species that showed superior survival and growth in these acid rock substrates included Elymus canadensis, Danthonia interrnedia, Sporobolus wrightii, Poa nemoralis, and Hesperostipa cornata. Additional

Assessment of 2,4,6‐trinitrotoluene toxicity in field soils by pollution‐induced community tolerance, denaturing gradient gel electrophoresis, and seed germination assay

AbstractDetermining the toxicity of contaminants to soil organisms under field conditions is hampered by site‐specific and temporal factors that modulate contaminant availability. Assessing the pollution‐induced community tolerance (PICT) of indigenous microbial communities integrates these complex environmental factors. The purpose of this study was to determine if the PICT response was proportional to 2,4,6‐trinitrotoluene (TNT) concentrations in soil, if changes detected by PICT were also evident in soil microbial community composition, and if the PICT response correlated with phytotoxicity assays. Microorganisms extracted from TNT‐contaminated field soils were mixed with a solution containing six different concentrations of TNT and inoculated into Biolog ECO plates. The utilization rate of substrates was determined over a 7‐d period. Denaturing gradient gel electrophoretic analysis of a portion of the gene encoding 16S rDNA described the structure of the soil microbial community. Phytoindicators (Poa compressa and P. palustris L.) of TNT pollution were identified and used to assess TNT phytotoxicity in soil samples. The TNT (in Biolog wells) greatly inhibited microbial communities from locations with low in situ TNT exposure. The inhibition of microbial use of L‐asparagine, L‐phenylalanine, and D‐glucosaminic acid by TNT (in Biolog wells) increased as TNT concentration in soil decreased. Locations differing in ECO‐PICT response also differed in their microbial community composition and TNT phytotoxicity. Decreased phytotoxicity of field soils corresponded to decreases in PICT. The results from this study indicated that ECO‐PICT is an effective assay to rapidly detect TNT exposure and toxicity in soil microbial communities.

Studies on the flora and vegetation of the Golestan National Park*, NE Iran. II. A new Poa and some new and noteworthy grass records for Iran

Poa golestanensis H. Scholz &amp; Akhani spec. nov. is described from the Golestan National Park, NE Iran. The following species are added to the grass flora of Iran from that area: Alopecurus aequalis Sobol., Cleistogenes serotina (L.) Keng, Heteropogon contortus (L.) P. Beauv. ex Roem. et Schult., Hordelymus europaeus (L.) Harz. The occurrence in Iran of Poa compressa L., P. densa Troitsky, and Bothriochloa bladhii (Retz.) S.T. Blake which were not mentioned in Rechinger's Flora Iranica but were reported in later papers is confirmed. The maps of distribution in the Park are provided for the treated species.

Polyamine concentrations in four Poa species, differing in their maximum relative growth rate, grown with free access to nitrate and at limiting nitrate supply

Polyamines are thought to play a role in the control of inherent or environmentally-induced growth rates of plants. To test this contention, we grew plants of four grass species, the inherently fast-growing Poa annua L. and Poa trivialis L. and the inherently slow-growing Poa compressa L. and Poa pratensis (L.) Schreb., at three levels of nitrate supply. Firstly, plants were compared when grown with free access to nitrate, allowing the plants to grow at their maximum relative growth rate (RGRmax). Secondly, we compared the plants when grown with relative nitrate addition rates of 100 and 50 mmol N (mol N)−1 day−1 (RAR100 and RAR50, respectively).