Leaf-Atmosphere NH3 Exchange in Barley Mutants with Reduced Activities of Glutamine Synthetase

Mutants of barley (Hordeum vulgare L. cv Maris Mink) with 47 or 66% of the glutamine synthetase (GS) activity of the wild type were used for studies of NH3 exchange with the atmosphere. Under normal light and temperature conditions, tissue NH4+ concentrations were higher in the two mutants compared with wild-type plants, and this was accompanied by higher NH3 emission from the leaves. The emission of NH3 increased with increasing leaf temperatures in both wild-type and mutant plants, but the increase was much more pronounced in the mutants. Similar results were found when the light intensity (photosynthetic photon flux density) was increased. Compensation points for NH3 were estimated by exposing intact shoots to 10 nmol NH3 mol-1 air under conditions with increasing temperatures until the plants started to emit NH3. Referenced to 25[deg]C, the compensation points were 5.0 nmol mol-1 for wild-type plants, 8.3 nmol mol-1 for 47% GS mutants, and 11.8 nmol mol-1 for 66% GS mutants. Compensation points for NH3 in single, nonsenescent leaves were estimated on the basis of apoplastic pH and NH4+ concentrations. These values were 0.75, 3.46, and 7.72 nmol mol-1 for wild type, 47% GS mutants, and 66% GS mutants, respectively. The 66% GS mutant always showed higher tissue NH4+ concentrations, NH3 emission rates, and NH3 compensation points compared with the 47% GS mutant, indicating that NH4+ release was curtailed by some kind of compensatory mechanism in plants with only 47% GS activit

Preface "Processes controlling the exchange of ammonia between grassland and the atmosphere (GRAMINAE) – results from the Braunschweig field experiment"

No abstract availabl

Authentication of organically grown plants - advantages and limitations of atomic spectroscopy for multi-element and stable isotope analysis

Organic food products are believed to be healthier, safer and more environment-friendly than their conventional counterparts and are sold at premium prices. Consequently, adulteration of organic plants and fraudulent activities for economic profit are increasing. This has spurred the development of sophisticated analytical procedures for testing authenticity. We review the use of multi-element and stable-isotope analysis based on atomic spectroscopy for discriminating between organic and conventional plants. We conclude that inductively-coupled plasma-mass spectrometry, stable-isotope analysis of bulk plant tissue, and compound-specific isotope analysis based on isotope ratio-mass spectrometry are promising tools for documenting the fertilization history of organic plants. However, these techniques are challenged by the potential diversity of fertilization practices of organic and conventional plant production. We therefore recommend that analytical techniques are combined and coupled with chemometrics to develop statistical models that can classify the agricultural origin of plant products

Contribution of different grass species to plant-atmosphere ammonia exchange in intensively managed grassland

Species diversity in grasslands usually declines with increasing input of nitrogen from fertilizers or atmospheric deposition. Conversely, species diversity may also impact the build-up of soil and plant nitrogen pools. One important pool is NH3/NH4+ which also can be exchanged between plant leaves and the atmosphere. Limited information is available on how plant-atmosphere ammonia exchange is related to species diversity in grasslands. We have here investigated grass species abundance and different foliar nitrogen pools in 4-year-old intensively managed grassland. Apoplastic pH and NH4+ concentrations of the 8 most abundant species (Lolium perenne, Phleum pratense, Festuca pratensis, Lolium multiflorum, Poa pratensis, Dactylis glomerata, Holcus lanatus, Bromus mollis) were used to calculate stomatal NH3 compensation points. Apoplastic NH4+ concentrations differed considerably among the species, ranging from 13 to 117 μM, with highest values in Festuca pratensis. Also apoplastic pH values varied, from pH 6.0 in Phleum pratense to 6.9 in Dactylis glomerata. The observed differences in apoplastic NH4+ and pH resulted in a large span of predicted values for the stomatal NH3 compensation point which ranged between 0.20 and 6.57 nmol mol−1. Three species (Lolium perenne, Festuca pratensis and Dactylis glomerata) had sufficiently high NH3 compensation point and abundance to contribute to the bi-directional NH3 fluxes recorded over the whole field. The other 5 grass species had NH3 compensation points considerably below the atmospheric NH3 concentration and were thus not likely to contribute to NH3 emission but only to NH3 uptake from the atmosphere. Evaluated across species, leaf bulk-tissue NH4+ concentrations correlated well (r2=0.902) with stomatal NH3 compensation points calculated on the basis of the apoplastic bioassay. This suggests that leaf tissue NH4+ concentrations combined with data for the frequency distribution of the corresponding species can be used for predicting the NH3 exchange potential of a mixed grass sward. [Abstract from: http://www.biogeosciences.net/6/59/2009/bg-6-59-2009.html

Multi-element plant tissue analysis using ICP spectrometry

Plant tissue analysis is a valuable tool for evaluating the nutritional status and quality of crops and is widely used for scienti fi c and commercial purposes. The majority of plant analyzes are now performed by techniques based on ICP spectrometry such as inductively coupled plasma—optical emission spectroscopy (ICP-OES) or ICP—mass spectrometry (ICP-MS). These techniques enable fast and accurate measurements of multielement pro fi les when combined with appropriate methods for sample preparation and digestion. This chapter presents state-of-the-art methods for digestion of plant tissues and subsequent analysis of their multielement composition by ICP spectrometry. Details on upcoming techniques, expected to gain importance within the fi eld of multielement plant tissue analysis over the coming years, are also provided. Finally, attention is given to laser ablation ICP-MS (LA-ICP-MS) for multielement bioimaging of plant tissues. The presentation of the methods covers instructions on all steps from sampling and sample preparation to data interpretation