Agrostis Tenuis Sibth Research Articles

Chemical and ecotoxicological effects of the use of drinking-water treatment residuals for the remediation of soils degraded by mining activities

The aim of this study was to evaluate the use of drinking-water treatment residuals (DWTR) in the amendment of a soil affected by mining activities (Aljustrel mine, Portuguese sector of the Iberian Pyrite Belt), considering the effects on its chemical, biochemical and ecotoxicological characteristics. The DWTR had neutral characteristics (pH 6.7) and an organic matter (OM) content of 575 g kg−1 dry matter (DM), which makes them a potential amendment for the remediation of mine degraded soils, as they may correct soil acidity and reduce the extractable metal fraction. An incubation assay, with soil and DWTR, with or without lime, was carried out to test the doses to be used in the assisted-phytostabilization experiment. Based on the results obtained, the doses of DWTR used were the equivalent to 48, 96, and 144 t DM ha−1, with and without lime application (CaCO3 11 t DM ha−1). Agrostis tenuis Sibth was used as the test plant. Some amendments doses were able to improve soil characteristics (pH and OM content), to decrease metal extractability by 0.01 M CaCl2 (especially for Cu and Zn), and to allow plant growth, that did not occur in the non-amended soil. Copper, Pb and Zn concentrations in the plant material were lower than the maximum tolerable level for cattle feed, used as an indicator of risk of entry of those metals into the human food chain. The simultaneous application of DWTR (96 and 144 t ha−1), with lime, allowed a reduction in the mine soil ecotoxicity, as evaluated by some lethal and sub-lethal bioassays, including luminescence inhibition of Vibrio fischeri, Daphnia magna acute immobilization test, mortality of Thamnocephalus platyurus, and 72-h growth inhibition of the green microalgae Pseudokirchneriella subcapitata. However, DWTR were unable to increase soil microbial activity, evaluated by dehydrogenase activity, an important soil-health indicator. Also, OM content and NKjeldahl, concentrations increased slightly but remained low or very low (P and K extractable concentrations were not affected). In general, the bioassays highlighted a decrease in soil ecotoxicity with the presence of lime and DWTR (144 t DM ha−1). In conclusion, DWTR are recommended to amend acidic soils, with high concentrations of trace elements, but an additional application of organic or mineral fertilizers should be considered.

Ефективність впливу біопрепаратів на проростання і схожість зернівок Festuca rubra L. та Agrostis tenuis Sibth.

Lawns of modern city serve as ecostabilizing element of transformed environment. Plants of Festuca rubra L. and Agrostis tenuis Sibth. are perennial grassy plants, essential components of multifunctional high-decorative grass surfaces. Usage of biologics nanoscale particles can increase plant resistance to environmental factors and intensify their processes of growth and development. The processes of energy germination and germination of turfgrass species are decisive step during formation of high-quality lawns. We established energy germination and germination of seeds F. rubra and A. tenuis under universal multielements biopreparations. Morphometric parameters of plant leaf plates studied on 7 and 14 days of cultivation. The intensity of the formation of roots of plants and their morphometry analyzed. On the 7 th day of cultivation seeds of plants under usage of biopreparations increased rates of energy germination to 7-15% compared to control, but on 14 th - only 5%. Studies indicate that usage of biopreparations intensifies the processes of formation of root system and leaf plates.

Performance of Low-input Turfgrass Species as Affected by Mowing and Nitrogen Fertilization in Minnesota

In Minnesota, most lawns and higher cut turfgrass areas consist primarily of species such as kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) that require significant management inputs such as frequent mowing and nitrogen fertility. Several studies have shown that other species have the potential to be used more widely on home lawns in Minnesota; however, little is known about the management requirements of these species. In this study, we evaluated the performance of several alternative grass species under varying mowing and nitrogen fertility regimes at two sites in Minnesota in 2010 and 2011. Hard fescue [Festuca trachyphylla (Hackel) Krajina] showed the most consistent performance across management regimes, seasons, and locations. Colonial bentgrass (Agrostis tenuis Sibth.) showed good spring and fall turf quality, but suffered from excess thatch development and disease incidence. ‘Barkoel’ prairie junegrass [Koeleria macrantha (Ledeb.) Schult] maintained acceptable turf cover throughout the trial, whereas unimproved native prairie junegrass populations did poorly regardless of management level. Tufted hairgrass [Deschampsia cespitosa (L.) P. Beauv.] did not perform consistently in the trial due to summer stress. Our results show that hard fescue, colonial bentgrass, and ‘Barkoel’ prairie junegrass performed well regardless of mowing height or fertility treatment and could be used to a greater degree as low-input turfgrasses in Minnesota.

Soil acidification and liming in grassland production and grassland soil fertility in Slovenia

This paper reviews the evidences on grassland soil acidity and liming in relation to soil processes and herbage production. There is also an outline of the present state of soil acidity and acidity-related traits – contents of organic matter (OM), phosphorus (P) and potassium (K) in Slovene grassland. In grassland, soil acidification is an ongoing process under humid climate conditions. It is mainly driven by leaching of nutrients, net loss of cations due to retention in livestock products, use of physiologically acid fertilizers, acid rain and N2 fixation. This process is reduced by strong pH buffering capacity of the soil and by physiologically basic fertilizers. Acid grassland soils in Slovenia are widely distributed in spite of the fact that 44% of the total land has developed from a carbonate parent material. Of the 1713 grassland soil samples analysed during 2005-2007 45% were regarded as acid ones (pH < 5.5; in KCl), 57% as soils with very low P status (˂ 6 mg P2O5/100 g soil) and 22% as soils with very low K status (˂ 10 mg K2O/100 soil). Increased content of soil organic matter was identified for alpine pastures (˃ 10 % OM in 44% of samples), mainly as a result of low decomposition rate. Liming of acid grassland soils did not always reflect in a higher herbage yield. The cause for this inefficiency is plant composition of grassland. Thus, many grassland plants with relatively high production potential have adapted to acid soil conditions. To illustrate the inconsistent liming effect three researches are reviewed. In the first two researches liming along with fertilizer application did not increase the yield comparing to the fertilized control while in the third research the increase amounted 26 %. Liming improves considerably botanical composition of the acid grassland (e.g. sward where Common Bent – Agrostis tenuis Sibth. – prevails) and thus indirectly affects palatability and nutritive value of herbage. Grassland liming has a weak direct effect on herbage quality – it usually increases content of Ca and sometimes decreases Mg in herbage. The latter effect is rare. In Slovenia, ameliorative liming is advised for grassland soils with pH < 5.0 and maintenance liming for grassland soils with pH < 6.0 (pH in KCl or CaCl2).

PERFORMANCES OF SOME COOL SEASON TURFGRASS SPECIES IN MEDITERRANEAN ENVIRONMENT: I. Lolium perenne L., Festuca arundinacea Schreb., Poa pratensis L., and Agrostis tenuis Sibth

The commitment to turf research is more recent and is challenged by the diversity of climatic conditions occurring throughout the Anatolian peninsula in Turkey, thereby complicating the recommendation of species and cultivars. Assessing the peculiarities of turfs during the growing period and the efficient use of turf for establishing lawns requires field evaluation of the existing cultivars particularly in the sites with a Mediterranean climate. Our study is aimed at evaluating the adaptability and quality of the popular cultivars (introductions) of cool season turfgrass species in a Mediterranean site in western Turkey, Bornova/IZMIR. Six cultivars of perennial ryegrass (Lolium perenne L.), four cultivars of tall fescue (Festuca arundinacea Schreb.), four cultivars of Kentucky bluegrass (Poa pratensis L.) and four cultivars of colonial bentgrass (Agrostis tenuis Sibth) were tested for 3 years in a replicated experimental block group design. Turf cover, colour and quality traits of each cultivar in each species were evaluated by using a visual score (1-9) and assessed in each season from 2003 to 2005. Cultivars of tall fescue and to some extent perennial ryegrass species were better able than those of Kentucky bluegrass and colonial bentgrass to cope with the existing Mediterranean climatic condition. All species performed better in winter, spring and autumn than summer season, except for tall fescue. Kentucky bluegrass and colonial bentgrass cultivars were not found recommendable for Mediterranean environment.

Differentiation of populations of Agrostis tenuis Sibth. and Dactylis glomerata L. in the flood meadow habitats of the Luga river

The purpose of our study was to examine the structure of the variation in the population of two grass species and the nature of differentiation of their populations in various habitats. We used data of the 13 morphological traits in 16 populations of Dactylis glomerata L. and 9 populations Agrostis tenuis Sibth. in 4 types of habitats of flood meadows performed in the North-West region of Russia. The statistical data processing was performed in the package STATISTICA 5.0 for Windows (Statsoft Inc., USA). Results were showed, that the size of individuals is a direct response to the variation of richness of environmental conditions. The shape components, which reflect genetic diffwerentiation of populations due to genetic drift and natural selection, are less variable.

Transgenic Plants of Colonial Bentgrass from Embryogenic Callus via Agrobacterium-mediated Transformation

Colonial bentgrass (Agrostis tenuis Sibth. Fl. Oxen.) is a cool-season turfgrass used on fairways in golf courses. The object of this study was to develop a more efficient, reliable and repeatable approach in transforming the grass using Agrobacterium (strain LBA4404), in which β-glucuronidase (gus) gene was used as a reporter and hygromycin phosphotransferase (hpt) gene as a selectable marker. This vector was effective in transforming 7-week-old calluses derived from mature seeds cultured on MS medium supplemented with 2,4-D. A two-step solid medium selection with increasing hygromycin concentration (from 50 to 70 mg l−1) was used to obtain resistant calluses. Hundreds of transgenic plants have been produced from several independent transformed calluses. The presence of functional β-glucuronidase (GUS) was detected in hygromycin-resistant calluses, young leaves and roots of transgenic plants. The transgenic plants collected from greenhouse showed strong resistance to 50 mg l−1 hygromycin solution. Four putative transgenic plants and one control plant were randomly chosen and analyzed by Southern blot analysis. Bands corresponding to the hpt gene were clearly shown in transgenic plants.

Agrobacterium-mediated transformation of herbicide resistance in creeping bentgrass and colonial bentgrass.

Embryogenic calli were induced from the seeds of creeping bentgrass (Agrostis palustris Huds.) cv. Regent and colonial bentgrass (Agrostis Tenuis Sibth. Fl. Oxen.) cv. Tiger. The embryogenic calli were precultured on fresh medium for 4-7 days and then co-cultivated with Agrobacterium tumefaciens, LBA4404, which contains plasmid vector-pSBGM harboring bar coding region, synthetic green fluorescent protein (sGFP) coding region and matrix attachment region (MAR). After 3 days of co-cultivation, the calli were washed thoroughly and transferred to MS medium containing 2 mg/L of 2, 4-D, 12-15 mg/L phosphinothricin (PPT) and 250 mg/L of cefotaxime. After 2-3 months of selection, the actively growing calli of 'Regent' and 'Tiger' were transferred to MS medium with 12-15 mg/L PPT and 250 mg/L cefotaxime for regeneration. The putative transformants were maintained on MS medium with 3 mg/L PPT for long period but control died within 1 month. After establishing in greenhouse, the transformants also showed strong resistance to 0.4% of herbicide Basta but control plants died within 2 weeks. Under confocal microscope, both young leaves and roots showed significant GFP expression. PCR analysis revealed the presence of a DNA fragment of GFP gene at the expected size (380 bp) in the transformants and its absence in a randomly selected control plant.

Methylation of arsenic in vitro by cell extracts from bentgrass (Agrostis tenuis): effect of acute exposure of plants to arsenate.

Compared with microorganisms and mammalian tissues, information is scant on the enzymes responsible for arsenic metabolism in plants. This study investigated the arsenic methylation activities extractable from leaves and roots of Agrostis tenuis Sibth. plants grown in complete nutrient media and exposed to arsenate (135-538 M) for 3 d before harvesting. Methylation activity was determined in leaf and root extracts using an in vitro assay based onS-[3H-methyl]adenosyl-L-methionine (3H-SAM) with either arsenite or arsenate as substrate. Arsenite methylation activity was low in leaf extracts from plants not exposed to arsenate, but was greatly enhanced after acute exposure, with the induced methylation activity greatest in extracts from plants exposed to 269 M arsenate. Monomethylarsonate (MMA) was the predominant early product, but over longer assay times dimethylarsinate (DMA) accumulated at the rate of 660 amol mg protein-1 min-1 to levels exceeding MMA. With arsenate as substrate, methylation activity was much lower than with arsenite, implying that arsenite is the preferred substrate for methylation. Root extract assays exhibited no DMA, however small amounts of MMA were formed with arsenite as substrate. In contrast to leaves, the methylation activity did not increase in root extracts from plants exposed to arsenate. These findings suggest that arsenate in the plant growth medium was taken up by the roots and converted to arsenite before methylation proceeded in the leaves, accompanied by induction of arsenic methyltransferase activities.

Effect of grazing history, experimental defoliation, and genotype on patterns of silicification in Agrostis tenuis Sibth.

We examined the effect of grazing exclosures in reducing the concentration of silica, the effect of experimental defoliation on silica accumulation, and the existence of genotypic variability in silica content in plants of Agrostis tenuis. Silica content of plants was higher in heavily grazed areas than within exclosures during the summer, but no significant differences in content were found in winter. Laboratory experiments indicated that there were significant differences among genotypes in their silica content. Some genotypes increased their silica content after clipping at intervals of 14 days but most of them reduced their silica content when clipped weekly. The existence of a significant genotype-clipping treatment interaction term showed that silica accumulation as a response to clipping varied among genotypes, and may provide the basis for microevolutionary changes in natural populations of A. tenuis. However, the possibility of silica acting as a defence was not supported when caterpillars of the graminivorous Lepidoptera, Pararge aegeria, fed on plants. The caterpillars fed more extensively on plants from grazed areas, which had a higher silica content. We conclude that there is some genetic variation in patterns of silica accumulation in plants of A. tenuis and that different grazing histories lead to differences in silica content of plants. Although the effect of silica concentration on large herbivores remains uncertain, herbivores can exert an effect on the silica content of the leaf blades of A. tenuis.

Agrostis castellana (Poaceae), Dominant Agrostis Species, Found in Bent Grass Pastures in South-eastern Australia

There is considerable uncertainty that the traditional identification of bent grasses in south-eastern Australia as Agrostis capillaris L. (Syn. Agrostis tenuis Sibth.) is correct, due to a history of confusing nomenclature and mis-identification. Bent grass is considered a weed of pastures in the high-rainfall zone of south-eastern Australia and thus the correct identity of bent grass may have implications for its management and control. Populations of bent grass were sampled from 42 pastures in south-eastern Australia and Agrostis castellana Boiss. et Reuter, rather than A. capillaris, was found to be the dominant species of Agrostis in 33 out of 42 bent grass pastures sampled. Five of the nine pastures sampled in Tasmania contained A. capillaris as opposed to only 1 of the 33 pastures sampled in Victoria. Agrostis castellana had not been identified in Victoria or Tasmania prior to this work. Since A. castellana grows more vigorously by rhizomes than A. capillaris, control measures recommended for A. capillaris may not be relevant for bent grass pastures in south-eastern Australia. Ligule length, ligule width and width of lamina, measured to determine whether species of bent grass could be easily distinguished in the field, did not distinguish adequately between A. castellana and A. capillaris.

Species for Low‐Input Sustainable Turf in the U.S. Upper Midwest

AbstractLow‐input sustainable turf (LIST) management represents a resource‐efficient option in maintaining uniform, persistent turf. What species are best suited to such management needs to be established. To this end, 12 hardy species were evaluated for 3 yr in Illinois, Indiana, Iowa, Michigan, Missouri, Ohio, and Wisconsin: crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. ‘Fairway’, ‘Ephraim’, and ‘Ruff’], streambank wheatgrass [Agropyron riparium Scribn. & Smith ‘Sodar’; syn. Elymus lanceolatus (Scribn. & J.G. Smith) Gould subsp. lanceolatus], Canada bluegrass (Poa compressa L. ‘Reubens’), hard fescue [Festuca ovina var. duriuscula (L.) Koch ‘Durar’; syn. F. lemanii T. Bastard], sheep fescue (F. ovina L. ‘Covar’ and common), tall fescue (F. arundinacea Schreb. ‘Alta’), bulbous bluegrass (P. bulbosa L.), alpine bluegrass (P. alpina L.), redtop (Agrostis alba L. ‘Reton’; Agrostis gigantea Roth), roughstalk bluegrass (P. trivialis L. ‘Colt’), colonial bentgrass (Agrostis tenuis Sibth. ‘Exeter’; syn. Agrostis capillaris L.), and buffalograss [Buchlöe dactyhides (Nutt.) Engelm. ‘Texoka’ and ‘NE‐315’]. AH were field‐established and compared at three mowing heights: 3.8 cm, 7.6 cm, and no mowing. Quality ratings were based on uniform persistence. Tall fescue and common sheep fescue were the best and most broadly adapted to LIST. In Iowa, hard fescue, Canada bluegrass, and crested wheatgrass also did well. Colonial bentgrass was best adapted in Missouri. Redtop and roughstalk bluegrass grew better in a north‐south area from Wisconsin through central Illinois to Missouri. The buffalograsses excelled in Ohio and southern Illinois. Over all species, the 7.6‐cm mowing height allowed the best turf quality. Specifically, tall fescue, colonial bentgrass, redtop, and common sheep fescue performed best at the 7.6‐cm mowing height. Covar sheep fescue, hard fescue, Canada bluegrass, and Fairway crested wheatgrass could not maintain persistent stands under the 3.8‐cm mowing height. No mowing resulted in intermediate levels of quality with all species. A 7.6‐cm mowing height would be appropriate for testing species in LIST within the seven‐state region used in this study.

Agronomic and nutritional effects of Linz-Donawitz slag application to two pastures in Northern Spain

Most grassland soils in western European countries are acidic in their natural state and require a liming material to bring them to their optimum pH. A study was conducted to determine whether Linz-Donawitz (LD) slag, a by-product of the iron and steelmaking industry, could be used as a dolomitic agent for pastures. Six rates of slag (0, 1, 1.5, 3, 5, and 7.5 t ha−1), with and without fertilizer, were investigated for their effects on soil properties, pasture yield and botanical composition, and herbage mineral concentrations. The three-year study was conducted on a newly established pasture of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), and white clover (Trifolium repens L.), and on a resident pasture dominated by Yorkshire fog (Holcus lanatus L.) and browntop (Agrostis tenuis Sibth.). Application of slag increased soil pH (0.15 and 0.11 units per ton of slag applied at Derio and Abadiano, respectively) and decreased Al percentage of the soil complex to levels not considered harmful to plant growth. Exchangeable Ca increased markedly and exchangeable Mg slightly. In general, herbage Ca and Mg concentrations increased accordingly to their increase in the soil, while Fe, Mn, Cu, and Zn decreased with increasing rates of slag. LD slag appears to be a useful liming material for correcting soil acidity in pasture scils, and for increasing Ca and Mg, and decreasing Mn concentrations, in herbage.

Salinity Effects on Bentgrass Germination

Duplicate studies were conducted to determine salt tolerance during germination of eight bentgrass (Agrostis spp.) cultivars commonly used for overseeding warm-season turf species, such as bermudagrass (Cynodon spp.) putting surfaces. Bentgrass seeds were germinated on agar salinized with 0, 4000, 8000, 12,000, or 16,000 mg·liter-1, with the highest rate approaching one-half seawater salinity. Total germination decreased linearly or quadratically for specific cultivars as salinity increased. Time necessary to reach 50% germination across all salt concentrations was shortest for `Highland' colonial (Agrostis tenuis Sibth) and `Seaside' creeping (A. palustris Huds.) bentgrass (≈3.7 days); intermediate for `Kingstown' velvet (A. canina L.) and `Streaker' red top (A. alba L.) bentgrass (≈4.5 days); and longest for `Penneagle' creeping, `Penncross' creeping, `Exeter' colonial, and `Pennlinks' creeping bentgrass (≈5.3 days). Salt concentrations necessary to reduce germination to 90%, 75%, and 50% indicated that `Streaker' red top and `Seaside' creeping bentgrass were the most salt-tolerant cultivars. `Kingstown' velvet, `Exeter' colonial, and `Highland' colonial bentgrass were intermediate, while `Pennlinks', `Penncross', and `Penneagle' creeping bentgrass were the most salt-sensitive cultivars.

Tolerances of different populations of three grass species to cadmium and other metals

The tolerance of seedlings of different seed populations of three grass species ( Festuca rubra L., Agrostis tenuis Sibth. and Arrhenatherum elatius J. and C. Presl—derived from a range of habitats) of the metals Cd, Zn, Cu, Pb and Ni was determined by means of relative root growth in metal-free and metal-enriched culture solutions. It was shown that all populations originating from metal-contaminated habitats possessed ‘multiple-metal-tolerance’, i.e. tolerance to more than one of the metals tested. Tolerance was most pronounced of those metals which were abundant in the original soils. A single population exhibited a remarkable Ni-tolerance, although this metal was not elevated in the population's natural habitat. The highest Cd-tolerance was found in populations which were also highly Zn/Pb-tolerant whereas Cu/Pb-tolerant populations did not show a significantly increased tolerance to Cd in solution culture. However, when growing plants on a range of CdO-enriched soils, either of the populations from metal-contaminated locations was less affected by the treatment than the respective non-tolerant control population. Measurements of yield, tissue Cd concentrations and activities of the enzymes acid phosphatase and peroxidase were performed. From the results it was postulated that Cd-tolerance could be related to the maintenance of lower Cd concentrations in shoots; the presence of an internal mechanism of Cd-tolerance in shoots seemed unlikely in the populations investigated.

Tolerance of Red Fescue (Festuca rubra) and Bentgrass (Agrostisspp.) to Sethoxydim

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} is used to control weedy grasses in red fescue (Festuca rubraL. # FESRU andF. rubrassp.commutata), an important seed crop in Oregon. The sethoxydim rate required to reduce growth rate of 11 cultivars of red fescue and four cultivars of bentgrass (Agrostis tenuisSibth. # AGSTE andA. stoloniferaL. var.palustris# AGSST), a common contaminant in red fescue fields, by 50% (GR50) was determined in greenhouse and laboratory experiments. Field experiments compared only red fescue cv. ‘Pennlawn’ and bentgrass cv. ‘Penncross'. The GR50values for Pennlawn red fescue in the field, the greenhouse, and the laboratory were 30 kg ai/ha, 15 kg/ha, and 5300 μM, respectively. Penncross bentgrass was approximately 400, 1400, and 12 900 times more susceptible than Pennlawn red fescue in the field, in the greenhouse, and in laboratory experiments, respectively. Plants were at different growth stages in the different experiments. The xylene and surfactant used as a solvent for the technical grade sethoxydim was as toxic to red fescue without sethoxydim as when sethoxydim was included. Cultivars of red fescue differed in their response to sethoxydim, but cultivars of bentgrass did not. The GR50's of other species tested in the greenhouse were >4 kg/ha for annual bluegrass (Poa annuaL. # POAAN), 0.22 kg/ha for tall fescue (F. arundinaceaSchreb. # FESAR), 0.37 kg/ha for downy brome (Bromus tectorumL. # BROTE), and 0.017 kg/ha for Italian ryegrass (Lolium multiflorumLam. # LOLMU).

Seasonal pattern of pasture production and the contribution of low fertility tolerant grasses in oversown tussock grassland on the lower Otago Plateau

Abstract Three years' seasonal pasture production data for an established oversown tussock pasture on the lower Otago Plateau are presented. The mean annual yield of the low fertility tolerant grasses (LFTG), sweet vernal (Anthoxanthum odoratum L.), browntop (Agrostis tenuis Sibth.), soft brome (Bromus mollis L.), Kentucky bluegrass (Poapratensis L.), and crested dogstail (Cynosurus cristatus L.) was 2673 kg dry matter (DM)/ha compared with 3190 kg DM/ha for ryegrass (Lolium perenne L.). Only in autumn were the yields of LFTG significantly lower than ryegrass (304 and 619 kg DM/ha respectively). The pattern of pasture production was closely related to seasonal rainfall. The results are discussed in the context of the overall management problems faced by runholders in the area, and strategies to develop more reliable and productive pastures are outlined. Improvement of ryegrass and clover content is considered in relation to stock, pasture, fertiliser, and pest management.

STUDIES ON THE TOLERANCE TO SO2 OF GRASS POPULATIONS IN POLLUTED AREAS

SummaryThe development of acute and chronic sulphur dioxide (SO2) tolerance in lawn grass populations was studied by two approaches: the minimum time for tolerance to appear in Festuca rubra L., Lolium multiflorum Lam., L. perenne L., Phleum pratense L. and Poa pratensis L., was determined by comparison annually of plant samples from monoculture plots sown at a polluted site, with plants grown from the seed originally sown; the long term development of tolerance in F. rubra, D. glomerata L. and Agrostis tenuis Sibth. was also investigated by comparison of five lawns of different ages (1–c. 200 years) at a polluted site.Tolerance to acute SO2 injury was detected in L. perenne and Phleum pratense only three and four years after sowing, respectively. However, population samples of these two species, collected from the field three years later, showed no significant SO2 tolerance. An analysis using morphological and isozyme variation as criteria showed that the tolerant population consisted of a large number of different individual genotypes. The populations experienced a state of evolutionary flux with rapid selection first of the tolerant, and subsequently of the non‐tolerant phenotypes. The disappearance of tolerance coincided with declining ambient SO2 concentrations.The lawns of different ages were shown to represent an evolutionary series of increasing acute SO2 tolerance with age of lawn in F. rubra and A. tenuis. This demonstrated the continuing development of acute SO2 tolerance in grass populations over a prolonged period.The significance of the occurrence and rate of development of SO2 tolerance for grasslands in polluted areas is discussed.

Histology of several cool-season forage grasses digested by cellulase

Abstract Leaf blade sections (3 cm long) from the last fully collared leaf of plants from genotypes of perennial ryegrass (Lolium (multiflorum Lam. × perenne L.) × perenne L.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), and brown top (Agrostis tenuis Sibth.) were digested by a fungal cellulase solution. Light microscope observations showed there was a similar pattern of digestion by cellulase in all the species studied. Digestion occurred first in the mesophyll, followed by disappearance of the epidermis and phloem. Cellulase did not digest the cuticle, sclerenchyma, or xylem. The observed pattern of digestion of fresh leaf blades by cellulase was similar to that reported previously for rumen liquor, except that digestion by cellulase was faster. Differences in rate of degradation by cellulase were demonstrated among species and between genotypes of the same species. Digestion of fresh grass leaves by cellulase is a potentially useful screening technique for breeding forage g...

PASTURE COMPOSITION UNDER MIXED SHEEP AND GOAT GRAZING ON HILL COUNTRY

Hill country pasture was grazed by the following ratios of goats and sheep from 1979-l 983: 100% goats (Goat 100). 66% goats and 34% sheep (Goat 66)) 33% goats and 67% sheep (doat 33), 100% set-stocked sheep (Sheep 100) and 100% mobstocked sheep. Changes in botanical composition, herbage mass and herbage accumulation rate were measured by sample dissection, visual estimation and trimmed exclosure cages respectively on three slope classes (banks, slopes and tracks). Pastures grazed by goats developed Yorkshire fog IHolcus lanatus)- white clover (Trifolium repens L.) associations with strong white clover growth on all slope classes unlike sheep-grazed pastures which contained little white clover and were dominated by perennial' ryegrass (Lolium perenne L.) and browntop (Agrostis tenuis Sibth.). The herbage mass of 3000, 1830, 1410 kg DM/ha on banks, slopes and tracks respectively for Sheep 100 pastures contrasted with that on the Goat 100 pastures of 2030, 3750 and 4300 kg DM/ha. White clover was enhanced on all slope classes in the Goat 100 treatment. Annual herbage accumulation was greater on the Goat 100 than Sheep 100 pastures, 13.9 and 11.2 t DM/ha respectively. There was a close association between increased annual white clover accumulation and tofal herbage accumulation. The complementary nature of sheepandgoatgrazing behavioursuggeststhe possibility of increased meat and fibre production from mixed grazing. The implications of these results for future research are discussed. Keywords: Sheep, goats, herbage mass, herbage accumulation rate, botanical composition, slope classes, white clover (Trifolium repens L.), perennial ryegrass (Lolium perenne L.), Yorkshire fog (Holcus lanatusl, browntop (Agrostis tenuis Sibth.).