Horst Schulz

The identification and quantification of arsenic-induced phytochelatins—comparison between plants with varying As sensitivities

The results presented in this paper provide evidence for the role of phytochelatins (PCs) in the detoxification of arsenic in six nonhyperaccumulating plant species, Agropyron repens, Glecoma hederacea, Leonurus marrubiastrum, Lolium perenne,Urtica dioica and Zea mays, in a pot experiment with high phosphate treatment. These plants differed in their arsenic sensitivities and were selected to investigate whether PCs with longer chains in roots of arsenic-tolerant species are synthesized. Raised concentrations of total PCs were measured in plant species with a range of sensitivities to arsenic at equivalent levels of arsenic exposure, determined as the inhibition of root biomass. In addition, the production of PCs as a function of accumulated arsenic was studied. Long-term PC synthesis (over a 5-week period) was positively, but non-linearly correlated with arsenic, suggesting that probably not all As is bound by PCs. Moreover, it could be shown that the synthesis of different chain lengths of PCs is associated with differences in As tolerance. In the more tolerant grasses A. repens and L. perenne it was chiefly the dithiol PC2 which was measured. In contrast, the dominant PC species in the less tolerant plants U. dioica, G. hederacea, L. marrubiastrum and Z. mays was PC3, while PC2 and PC3 were detected as well.

Nitrogen isotope ratios in pine bark as an indicator of N emissions from anthropogenic sources

The article describes the use of Scots pine bark to identifynitrogen sources in eastern Germany, as well as background areas in Russia and Bulgaria, by using natural isotope ratios of total nitrogen (Nt) and individual N compoundssuch as ammonium (NH4+), nitrate (NO3-)and amid nitrogen (amide-N). The samples collected were analysed using an elemental analyser in connection with a gas isotope mass spectrometer (EA-IRMS). Natural 15N abundances in pine bark from impact areas suggest that the ammonium accumulated on the surface of the bark is releasedfrom livestock management. Bark of Scots pines growing near agricultural land had highly depleted δ15Nt values (between –8 and –12‰), while bark from background areas (unpolluted areas) displayed slightly negative δ15Nt values (mean 15Nt = –3.8‰). It is assumed that part of the N adsorbed on the bark surface is mainly derived from ammonia(mean 15Nt = –40.3‰) escaping from livestock housing and during the application of manure. This assumption is confirmed by experiments under controlled conditions in which manure samples were spread on soil. In addition, temporal and spatial variations of 15Nt abundances in pine bark from various locations in eastern Germany as wellas pine stands in Nature Park Dübener Heath are discussed.

Vitality analysis of Scots pines using a multivariate approach

Abstract Multivariate statistical methods were used to analyse the vitality of Scots pines (Pinus sylvestris L.) by means of various biochemical, physiological, and nutritional characteristics, irrespective of tree age and without site-specific information. The vitality model was developed in three steps. First, artificial neural networks were used to select a minimal set of biomarkers as input variables with respect to the output variable circular surface increment (regression problem). In the second step, vitality states were classified by using the selected biomarkers (cluster analysis). Finally, discriminant analysis was applied to assign Scots pines to one of four classified vitality states. Sulfate sulfur (SO42−-S), non-protein-nitrogen (NPN), arginine (Arg), and chlorophylla (Chla) proved to be the best dynamic input variables to reliably determine the vitality of Scots pines. As the results of regression problem solutions showed, the optimized neural network found growth responses to the driving variables that are valid for both young and mature pine stands. However, the sensitivity analysis of the neural network also indicated that of the four variables, sulfate is the least sensitive. Nevertheless, the sulfate response of the network can be successfully used to analyze the specific effects of multiple exposure on the vitality of Scots pines. To summarize final vitality model enables the vitality of Scots pines to be evaluated without reference to tree age or knowing the specific forest conditions.

Biochemical Parameters as Biomarkers for the Early Recognition of Environmental Pollution on Scots Pine Trees. II. The Antioxidative Metabolites Ascorbic Acid, Glutathione, α-Tocopherol and the Enzymes Superoxide Dismutase and Glutathione Reductase

Abstract Field investigations with Scots pine trees (Pinus sylvestris L.) were performed in eastern Germany, where ambient SO2, NOx and O3 concentrations differed significantly in 1992-99 at three sites, namely Neuglobsow (yearly mean SO2 in 1992: 9 μg m-3), Taura (yearly mean SO2 in 1992: 54 μg m-3 and Rösa (yearly mean SO2 in 1992: 73 μg m-3). To investigate the effects of SO2, NOx and O3 on antioxidants (superoxide dismutase, ascorbic acid, glutathione, glutathione reductase, α-tocopherol) and pigments including chlorophyll fluorescence as well as visible damage symptoms in the form of needle yellowing and tip necroses, needles of the 1st and 2nd age class from young and mature trees were collected at the sites every October. Eight years after the start of the field study in 1992, the ambient SO2 concentrations had decreased significantly at Neuglobsow (yearly mean SO2 in 1999: 4 μg m-3), Taura (yearly mean SO2 in 1999: 5 μg m-3) and Rösa (yearly mean SO2 in 1999: 5 μg m-3). NOx and O3 differed less at the three sites and showed no temporal variations. Whole needle glutathione continuously decreased, although concentrations were higher in needles of the 1 st and 2nd age class from the polluted sites Taura and Rösa than the unpolluted site Neuglobsow. The activities of glutathione reductase exhibited the same site-related differences and temporal variations and were correlated with concentrations of oxidized glutathione (GSSG). In contrast, the activities of the enzyme superoxide dismutase and the concentrations of whole needle ascorbic acid remained unchanged over the period. Only at the end of the investigation period did the concentrations of oxidized ascorbic acid (dehydroascorbate) increase in six-month-old needles at the polluted sites Taura and Rösa. Despite the clear decreases in SO2, the visible symptoms of needle tip necroses remained unchanged, especially at the polluted sites Taura and Rösa, although the needles contained higher pigment concentrations than needles from the unpolluted sites. The results of measurements with antioxidants as biomarkers for SO2-mediated stress in pine needles show that the adult Scots pine trees at the polluted sites suffered from greater oxidative stress than the needles from the less polluted site.

Ascorbat- und Glutathiongehalt in verschiedenartig schadstoffbeeinflußten Nadeln vonPinus sylvestris L.

ZusammenfassungIn Extrakten von Nadelmischproben (Pinus sylvestris L.) wurde der Gesamtgehalt von Ascorbat und Glutathion mittels HPLC-Methoden bestimmt. Dabei konnte die chromatographische Abtrennung von Glutathion durch Optimierung des Gradientenprofils verbessert werden.Die Untersuchungen erfolgten an Nadelproben aus Kiefernjung- und-altbeständen mit differenzierter SO2-Immission. Mit zunehmender Immissionsbelastung zeigten diesjährige Nadeln von Jungbeständen einen Anstieg im Gesamtascorbatgehalt. Der gleiche Effekt wurde für den Gesamtglutathiongehalt sowohl in Jung- als auch in Altbeständen beobachtet. Diese Befunde wurden mit Literaturangaben anderer Untersuchungssysteme (Versuche in Expositions- und Open-Top-Kammern) diskutiert.SummaryConcentrations of antioxidants ascorbate and glutathione in Scots pine needles (Pinus sylvestris L.) taken from trees in the field were determined using the HPLC technique. A modification of the gradient profile made it possible to achieve a better separation between glutathione and the derivatization reagent monobromobimane in the chromatogram.The needles were taken from pine trees 25 years and 60 years old, growing in areas with varying pollution. This years needles of young pine trees were characterized by an increase in the total ascorbate content related to rising amounts of atmospheric pollutants. A similar trend was observed for glutathione in both young and old trees. These results are discussed in comparison with literature data on related open-top chamber experiments.

Effect of raw humus under two adult Scots pine stands on ectomycorrhization, nutritional status, nitrogen uptake, phosphorus uptake and growth of Pinus sylvestris seedlings.

Ectomycorrhiza (EM) formation improves tree growth and nutrient acquisition, particularly that of nitrogen (N). Few studies have coupled the effects of naturally occurring EM morphotypes to the nutrition of host trees. To investigate this, pine seedlings were grown on raw humus substrates collected at two forest sites, R2 and R3. Ectomycorrhiza morphotypes were identified, and their respective N uptake rates from organic (2-(13)C, (15)N-glycine) and inorganic ((15)NH(4)Cl, Na(15)NO(3), (15)NH(4)NO(3), NH(4)(15)NO(3)) sources as well as their phosphate uptake rates were determined. Subsequently, the growth and nutritional status of the seedlings were analyzed. Two dominant EM morphotypes displayed significantly different mycorrhization rates in the two substrates. Rhizopogon luteolus Fr. (RL) was dominant in R2 and Suillus bovinus (Pers.) Kuntze (SB) was dominant in R3. (15)N uptake of RL EM was at all times higher than that of SB EM. Phosphate uptake rates by the EM morphotypes did not differ significantly. The number of RL EM correlated negatively and the number of SB EM correlated positively with pine growth rate. Increased arginine concentrations and critical P/N ratios in needles indicated nutrient imbalances of pine seedlings from humus R2, predominantly mycorrhizal with RL. We conclude that different N supply in raw humus under Scots pine stands can induce shifts in the EM frequency of pine seedlings, and this may lead to EM formation by fungal strains with different ability to support tree growth.

Measurement and regionalization of nitrogen deposition for the risk assessment of nitrogen leaching in agricultural landscapes

The connection between the emission of atmospheric nitrogen (N) and the risk of groundwater pollution is significant for protection of the landscape with respect to the resources. The usually unknown amount of atmospheric nitrogen deposition has a high impact on N balances and on the leaching of nitrogen into the groundwater. Therefore, the present paper deals with the correlation between N emission and scenarios of potential risk assessment on N leaching into groundwater. The airborne N input into an agricultural landscape between the Saxon towns Taucha and Eilenburg (near Leipzig, Saxony) was measured by using the bulk N deposition method, the total atmospheric N deposition method with the ITNI system, and the bark sampling method, by focusing the results on the measurement of N input (punctual and regionalized) and on extrapolations to the risk of N leaching for planning purposes. On the forest measurement point the airborne N input is approximately twice as high as that on the ‘open land’ measurement point (about 15 kg N ha−1 yr−1). Two scenarios were calculated using different results of N deposition measurements; the measurement methods are described in the paper. For scenario 1, an annual potential N leaching of up to 11.5 kg/ha−1yr−1 could be modelled by using regionalized nitrate-N deposition and ammonium-N deposition data for open land. For scenario 2, because of the much higher measured inputs of 59.7 kg N ha−1yr−1 following the results of the ITNI system, the N discharge is excessively higher with up to 25 kg N ha−1yr−1. Both scenarios have been produced on the basis of a regional N balance with a surplus of 28.8 kg ha−1yr−1 (period 1998–2003) including original data from farms. The regionalization of the total atmospheric N deposition offers a new way to integrate the nowadays-unknown components of the N deposition into the estimation of potential risks of N leaching into the groundwater. The results are of high importance for groundwater protection.

Experimentelle Untersuchungen zur Aufnahme und zum Stoffwechsel von Stickstoff in Wurzeln ausgewählter Bodenpflanzen aus naturnahen Ökosystemen

Mechanisms of diversity changes in plant communities on physiological level are examined up to now only inadequately. Therefore, the objective of these pot experiments was to study differential adaptations in root uptake of inorganic N as well as in intracellular N storage of key metabolites in plants from the floor vegetation of Scots pine forests (B. sylvaticutn, A. flexuosa, C. epigejos, V. myrtillus, R. idaeus, R. fruticosus). Fertilizers of 15N labelled 15NH4NO3 and NH4 15NO3 were applied to determine the N uptake and the accumulation of amino acids. The results show that the rates for ammonium and nitrate uptake (mg 15N g-1 d-1) correspond with the glutamine concentrations in the roots. The NH 4 + -tolerant ericaceous shrub V. myrtillus accumulates excessively glutamine and shows the lowest uptake for both N forms. In sharp contrast, the nitrophile blackberry R. fruticosus has a low glutamine accumulation and a much higher uptake for nitrate and ammonium. In consequence, nitrophile characteristics of plants result in high N uptake and in a reduced accumulation of N in glutamine. In addition, it can be shown that in contrast to NH4 +-tolerant plants, which accumulate ammonium in glutamine and arginine, nitrophile plants prefer asparagine as amino acid for the intracellular N storage.