M. J. Emes

Bio: M. J. Emes is an academic researcher from University of Manchester. The author has contributed to research in topics: Sphagnum cuspidatum & Sphagnum. The author has an hindex of 5, co-authored 6 publications receiving 152 citations.

Effects of an experimentally applied increase in ammonium on growth and amino-acid metabolism of Sphagnum cuspidatum Ehrh. ex. Hoffm. from differently polluted areas

Abstract: SUMMARY Sphagnum cuspidatum Ehrh. ex. Hoffm. was removed from a relatively remote moorland site at the Migneint, N. Wales and from Holme Moss, S. Pennines — a site that has been subjected to atmospheric pollution deposition for a period of at least the last 200 yr. When exposed to elevated ammonium (NH4+) concentrations (0·1 and 1·0 mM) under laboratory conditions for a period of 30 d, S. cuspidatum from N. Wales showed a marked reduction in growth, whereas in the S. Pennine population, growth was stimulated above that of the untreated control tissue at both 0·1 and 1·0 mM NH4+. The largest growth stimulation, however, was seen at 0·1 mM. The effects of increased NH4+ in the growth medium on tissue total chlorophyll concentration after 30 d exposure were similar in moss from both study sites. There was a small linear decline in chlorophyll concentration with increasing ammonium concentration. Moss from both sites was exposed to 0·1 mM NH4+ for a period of 20 d. There was a marked difference in the response of the different moss populations as indicated by changes in the concentrations of the individual amino acids; notably a dramatic transient increase in glutamine (three-fold), arginine (19-fold), and asparagine (fourfold) in the moss from N. Wales. In contrast, in the S. Pennine moss, changes in tissue amino-N concentration were very much smaller. Possible mechanisms to account for the intraspecific differences in response of the moss from the two study sites to increased ammonium concentrations are discussed.

Effects of the bisulphite ion on growth and photosynthesis in Sphagnum cuspidatum Hoffm.

Abstract: summary Shoots of Sphagnum cuspidatum Hoffm. were collected from two sites: one, a relatively unpolluted site in N. Wales, remote from pollution sources and the other, a grossly polluted site in the South Pennines.* Material from both sites was grown in the laboratory and exposed to artificial rainwater solution with and without bisulphite (HSO3) amendment (0.1 mM). Effects of exposure to HSO3 for up to 21 days on growth, photosynthesis, chlorophyll a fluorescence and chlorophyll concentrations were studied in the two Sphagnum populations. Application of HSO3 produced significantly less than maximum growth in Sphagnum from both sites. This effect was far greater, however, in the material from the unpolluted Welsh site. Photosynthesis in the Welsh material treated with HSO3 decreased steadily with time; after 21 days of exposure, photosynthetic oxygen evolution had ceased. This decrease was accompanied by a decrease in fluorescence quenching (as [(P – T)/P]), suggesting a gradual loss of water-splitting activity. In contrast, HSO3 initially stimulated photosynthesis in Sphagnum from the polluted site. Chlorophyll concentration was decreased in Spliagmtm from both sites in the presence of HSO3 Possible mechanisms of tolerance to HSO3 are discussed.

The relationship between extracellular metal accumulation and bisulphite tolerance in Sphagnum cuspidatum Hoffm.

Abstract: summary Sphagnum cuspidatum Hoffm. was collected from a remote site in N. Wales, and a polluted site in the S. Pennines. When added to artificial rainwater solution, HSO3− was oxidized to SO42−. The rate at which this oxidation occurred was modified differentially by the mosses from the two sites. S. cuspidatum from the S. Pennines promoted a rapid oxidation rate and disappearance of HSO3− was complete in 6 h. S. cuspidatum from N. Wales, on the other hand, achieved a very slow oxidation rate and HSO3− persisted in solution for more than 24 h. Prolonged exposure to HSO3− in the Welsh material caused damage to, and eventual death of, this material but not of the S. Pennine moss. The rates of HSO3− oxidation promoted by the mosses from the two sites appear to be related to the concentration of the transition metal ions, Fe(III), Mn(II), and Cu(II), present on the cell-wall cation-exchange sites. These metals, particularly Fe, present on the surface of the S. Pennine material catalysed a rapid chemical oxidation of HSO3− to SO42−. The increased levels of transition metals associated with the S. Pennine moss originate in the peat as a legacy of past pollution events at this site. Levels of Fe were approximately 100 times greater than those for Mn or Cu and 5–10 times higher on the S. Pennine moss than on that from N. Wales. Removal of these metal ions (using EDTA) from the surface of the S. Pennine material removed the HSO3− oxidizing ability of the moss, leading eventually to cell death. The ability to withstand high levels of HSO3− was conferred upon the Welsh moss by supplying Fe(m) in artificial rainwater solution under laboratory conditions. Transplanting Sphagnum from the Welsh to the S. Pennine site gave rise to a similar response. Nomenclature of mosses follows Smith (1978).

Short term effects of bisulphite on pollution‐tolerant and pollution sensitive populations of Sphagnum cuspidatum Ehrh. (ex. Hoffm.)

Abstract: summary Moss tissue from two distinct populations of Sphagnum cuspidatum from N, Wales (‘unpolluted’) and the S. Pennines (‘polluted’) was exposed to 0.2 mM HSO3− over a 24–26 h period. The rates of HSO2−, disappearance in the bathing solution were monitored in conjunction with tissue dark respiration, net photosynthetic rate and chlorophyll a fluorescence induction kinetics. Slow disappearance of HSO3− in the presence of moss tissue from N. Wales (40% of initial concentration remaining after 24 h) resulted in a rapid (< 2 h) loss of photosynthetic oxygen evolution, and a gradual marked decline in tissue dark respiration and chlorophyll fluorescence quenching. In the S. Pennine tissue, rapid HSO3− disappearance in the growth medium (complete after < 4 h) resulted in a marked recovery of photosynthetic and respiratory pathways after the initial inhibitory effects of HSO3− on these processes. Pretreating S. Pennine moss tissue with EDTA prior to exposure increased HSO3− residence time with consequent rapid decline in net photosynthetic rate, rendering the response of the moss similar to that from N. Wales (‘unpolluted’ site). In a second experiment, identical moss samples from the two study sites were exposed to 0.2 mM HSO3− for a period of 24 d. One set of plants from each population was prewashed in 5mM EDTA to remove extracellularly-bound cations prior to HSO3− exposure. Growth decrease was greater in the unpretreated moss N. Wales (74% with respect to tissue not exposed to HSO3−) than that from the S. Pennines (45.5%). After 10 days the pigments of the former were visibly bleached. No bleaching was observed in the latter. In the moss from N. Wales, removal of the extracellular cations with EDTA only slightly enhanced the effect of HSO3− on growth, whilst in the S. Pennine plants EDTA pretreatment resulted in a further growth reduction of 13%. The differential response of the moss from the two sites is discussed as a function of the extracellular transition metal concentration (Notably Fe) associated with the plants.

The Role of Bryophytes in Carbon and Nitrogen Cycling

Abstract: management. How does our behavior (including urban development and land-use, water consumption, pollution) influence the movement of energy, water, and elements at local, regional, national or global scales? Will perturbations to chemical and energy cycles alter existing controls on ecosystem processes, and can we learn enough about them for effective regulation? Plants are critical in regulating biogeochemical cycles. Their growth controls the exchange of gases that support life in our current biosphere, and affects soil development. As primary producers, they influence the distribution of energy for higher trophic levels. Understanding how plants influence ecosystem processes requires a multidisciplinary approach drawing on plant physiology and biochemistry, community ecology, and biogeochemistry. Due to their unique physiology and ecology, bryophytes differ from vascular plants in influencing cycles of elements, energy, and water. For example, bryophytes have evolved an effective water relation system. Poikilohydry and desiccation tolerance allow bryophytes to tolerate longer periods of water stress than vascular plants, and to recover quickly with rehydration. With poorly developed conduction systems, water and solutes are taken up over the entire plant surface. Lack of both gametophyte stomata and effective cuticles in many species allows free exchange of solutions and gases across cell surfaces. Thus bryophytes often serve as effective traps for water and nutrients. This also makes them more sensitive to atmospheric chemical deposition than vascular plants. Bryophytes also can tolerate a wide range of temperatures and are found in almost all terrestrial and aquatic environments, including harsh Antarctic environments where vascular plant cover is low (cf. Fogg 1998; Seppelt 1995). Without roots, bryophytes can colonize hard substrates like rock and wood that are poor habitat for vascular species. Bryophytes stabilize soils and prevent the loss of soil and nutrients via erosion, particularly on sand dunes (Martinez & Maun 1999) and in cryptogamic soil crusts (Eldridge 1999; Evans & Johansen 1999). Cation exchange on Sphagnum cell walls releases protons, generating acidity that may inhibit plant and microbial growth (Clymo 1963; Craigie & Maass 1966; Spearing 1972). Finally, bryophytes influence ecosystem succession (Brock & Bregman 1989) through terrestrialization of water bodies, deposition of benthic organic matter or paludification of upland systems. Bryophyte colonization often precedes the establishment of tree surfaces by other canopy-dwelling plants (Nadkarni et al. 2000). Due to their physiology and life history traits, bryophytes influence ecosystem functions by producing organic matter, stabilizing soils or debris, trapping sediments and water, and providing food and habitat for algae, fungi, invertebrates, and amphibians. In this review, my objectives are to highlight several mechanisms by which bryophytes influence carbon (C) and nitrogen (N) cycles within and fluxes from ecosystems. As such, I will focus on how bryophytes fix, intercept, transform, and/or release C and N. My goals are to 1) introduce important processes controlling inputs and outputs of C and N in both terrestrial and aquatic ecosystems, 2) review work on the growth, decomposition, and leaching of bryophyte material, as well as biotic and abiotic controls on these mechanisms, and 3) suggest areas for future research that would advance our understanding of bryophytes in biogeochemical cycling. Current address: U.S. Geological Survey, 345 Middlefield Rd. MS 962, Menlo Park, CA 94025 U.S.A. e-mail: mturetsky@usgs.gov

The deposition of atmospheric ammonia and its effects on plants

Abstract: SUMMARY Across Europe, total nitrogen deposition is increasing and, of this total, atmospheric ammonia can contribute up to 50–80%. Average deposition of ammonia in the UK is likely to be around 15–20 kg ha−1 yr−1, while in The Netherlands, which has some of the highest rates of deposition, this value is likely to be between 40 and 50 kg ha−1 yr−1. It is argued that because of the processes of assimilation and nitrification this ammonia is an acidifying pollutant. Ammonia taken up by plants is most likely to be directly assimilated and this uptake can have a strong effect on the nutrient imbalances of the plant. With root uptake in particular, anions are taken up in preference to cations. However, simple soil/plant nutrient measurements are unlikely to be a definitive means of monitoring ammonia pollution. This is because the processes of ammonia metabolism and acidification affect soil ion activity, mycorrhizas, plant uptake, and foliar leaching. These effects interact with acidity per se, and are compounded by the strong correlative co-deposition of ammonia with sulphur. Evidence for uptake of gaseous and wet deposited ammonia by leaves is presented. The exact mechanism of ammonia toxicity is still not really clear, but could be due to physiological perturbation, rather than to the direct toxicity of the ion. Assimilation of ammonia by leaves releases protons which can cause cellular acidosis, and has important implications for acid-base regulation in cells. This regulation depends on intrinsic features of the plant's metabolism, that is in turn dependent on the ecology of root versus leaf nitrogen nutrition under normal conditions. Certain species are more acidic in a leaf physiological sense and tend to be prone to damage by pollutants. Likewise, acidic habitats are particularly prone to damage through both eutrophication and the different capacities of plants both to utilize and to buffer against this nitrogen enrichment. The current evidence from The Netherlands suggests that the part this plays in perturbing the ecosystem should not be underestimated.

Ectomycorrhizal fungi : key genera in profile

Abstract: 1 Pisolithus.- 2 Suillus.- 3 Laccaria.- 4 Hebeloma.- 5 Rhizopogon.- 6 Tuber.- 7 Scleroderma.- 8 Amanita.- 9 Paxillus.- 10 Cantharellus.- 11 Lactarius.- 12 Cenococcum.- 13 Hysterangium.- 14 Thelephora.- 15 Resupinate Ectomycorrhizal Fungal Genera.

Nitrogen content and d15N signature of ombrotrophic Sphagnum plants in Europe: to what extent is the increasing atmospheric N deposition altering the N-status of nutrient-poor mires?

Abstract: Nitrogen concentration and delta(15)N signature of ombrotrophic Sphagnum mosses at different N deposition in Europe

Nitrogen fertilization reduces Sphagnum production in bog communities.

Abstract: The effects of increased nitrogen influx on Sphagnum growth and on interspecific competition between Sphagnum species were studied in a 3-yr experiment in mires situated in two areas with different rates of airborne N deposition. Sphagnum growth was recorded after various supplementary N influxes (0, 1, 3, 5 and 10 g m −2 yr−1) in hummocks and lawn communities. Sphagnum biomass production decreased with increasing N influx in both areas. After the first season at the low-deposition site, Sphagnum showed an increased growth in length with the intermediate N treatment, but in the second and third seasons the control treatment had the highest growth in length. Capitulum dry mass increased with increasing N influx. Sphagnum N concentration and N/P quotient were higher at the high- than at the low-deposition site. The low quotient at the low-deposition site, together with the initial growth increase with intermediate N supplements, indicates that growth was N-limited at this site, but our lowest N supplement was sufficient to reduce growth. The N treatments had no effect on interspecific competition between the Sphagnum species. This indicates that the species have similar responses to N. The species studied all occur naturally on ombrotrophic, N-poor sites and show low tolerances to increased N influx. Reduced Sphagnum production may affect the carbon balance, changing the mires from C sinks to sources.