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In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated... more
In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated capacity for phytochelatin production are compared with wildtype plants for the removal of heavy metals at different levels of contamination and under different climatic conditions. The studies are carried out with grey poplar (Populus tremula x P. alba), wildtype plants and plants overexpressing the gene for gamma-glutamylcysteine synthetase (gshI) from E. coli in the cytosol. The expression of this gene in poplar leads to two- to four-fold enhanced GSH concentrations in the leaves. In greenhouse experiments under controlled conditions these transgenic poplars showed a high potential for uptake and detoxification of heavy metals and pesticides. This capacity is evaluated in field experiments. Further aims of the project are to elucidate (a) the stability of the transgene under field conditions and (b) the possibility of horizontal gene transfer to microorganisms in the rhizosphere. The results will help to assess the biosafety risk of the use of transgenic poplar for phytoremediation of soils.
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ABSTRACT
Research Interests: Botany, Chemistry, Plant Biology, Biology, Experimental Botany, and 7 moreNitrate, Xylem, Nitrogen, Phloem, Abscisic Acid, Ammonium, and Shoot
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Research Interests: Botany, Chemistry, Plant Biology, Biology, Salt Stress, and 9 moreExperimental Botany, Nitrate, Xylem, Nitrogen, Phloem, Abscisic Acid, Ammonium, Long Distance, and Shoot(Experimental Botany, Nitrate, Xylem, Nitrogen, Phloem, Abscisic Acid, Ammonium, Long Distance, and Shoot)
(Experimental Botany, Nitrate, Xylem, Nitrogen, Phloem, Abscisic Acid, Ammonium, Long Distance, and Shoot)
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Anoxic conditions should hamper the transport of sugar in the phloem, as this is an active process. The canopy is a carbohydrate source and the roots are carbohydrate sinks. By fumigating the shoot with N2 or flooding the rhizosphere,... more
Anoxic conditions should hamper the transport of sugar in the phloem, as this is an active process. The canopy is a carbohydrate source and the roots are carbohydrate sinks. By fumigating the shoot with N2 or flooding the rhizosphere, anoxic conditions in the source or sink, respectively, were induced. Volume flow, velocity, conducting area and stationary water of the phloem were assessed by non‐invasive magnetic resonance imaging (MRI) flowmetry. Carbohydrates and δ13C in leaves, roots and phloem saps were determined.Following flooding, volume flow and conducting area of the phloem declined and sugar concentrations in leaves and in phloem saps slightly increased. Oligosaccharides appeared in phloem saps and after 3 d, carbon transport was reduced to 77%. Additionally, the xylem flow declined and showed finally no daily rhythm. Anoxia of the shoot resulted within minutes in a reduction of volume flow, conductive area and sucrose in the phloem sap decreased. Sugar transport dropped to below 40% by the end of the N2 treatment. However, volume flow and phloem sap sugar tended to recover during the N2 treatment.Both anoxia treatments hampered sugar transport. The flow velocity remained about constant, although phloem sap sugar concentration changed during treatments. Apparently, stored starch was remobilized under anoxia.
Research Interests: Botany, Water, Carbon, Biology, Starch, and 13 moreMedicine, Biological Sciences, Xylem, Sugar, Nitrogen, Sucrose, Phloem, Plant Roots, Oxygen, Carbohydrate metabolism, Castor Bean, Plant Leaves, and Shoot
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ABSTRACT
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ABSTRACTBeech seedlings from 11 German climatic provenances were exposed to a realistically timed drought treatment in a greenhouse experiment. The stable isotope composition of carbon (C) and nitrogen (N) was analysed in pooled bulk... more
ABSTRACTBeech seedlings from 11 German climatic provenances were exposed to a realistically timed drought treatment in a greenhouse experiment. The stable isotope composition of carbon (C) and nitrogen (N) was analysed in pooled bulk material of roots, stems and leaves, as well as in the aqueous extracts and starch fractions. The δ13C values increased in bulk samples (BS) of roots, stems and leaves by drought, although no leaf growth occurred during the experimental period. A clear drought effect on δ13C in aqueous extracts was detected in leaves. In aqueous extracts of stems and roots as well as in starch fractions of all organs, abundance of δ13C also tended to be increased by drought, but this effect was not statistically significant. For both δ13C and δ15N, enrichment was observed from the site of uptake/source to the site of use/sink. A gradient for δ13C in all fractions from leaves (−29.49, −28.89 and −27.85‰) to stems (−28.81, −27.48 and −26.98‰) and to roots (−27.60, −26.37 and −26.48‰) was detected in BS, aqueous extracts and starch, respectively. An opposite gradient for δ15N was found in BS: 1.59‰, 1.84‰ and 3.05‰ in roots, stems and leaves, respectively. δ15N was neither affected by drought in the BS nor in aqueous extracts, but an effect of provenance was observed. Particularly in roots and stems, drought‐sensitive provenances showed the strongest shifts in δ13C induced by drought and the lowest δ15N values. In the present experiment, δ13C values were more affected by the environmental factor drought, while δ15N values were more affected by the genetic factor provenance.
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Nitrogen isotope signatures in plants might give insights in the metabolism and allocation of nitrogen. To obtain a deeper understanding of the modifications of the nitrogen isotope signatures, we determined δ(15)N in transport saps and... more
Nitrogen isotope signatures in plants might give insights in the metabolism and allocation of nitrogen. To obtain a deeper understanding of the modifications of the nitrogen isotope signatures, we determined δ(15)N in transport saps and in different fractions of leaves, axes and roots during a diel course along the plant axis. The most significant diel variations were observed in xylem and phloem saps where δ(15)N was significantly higher during the day compared with during the night. However in xylem saps, this was observed only in the canopy, but not at the hypocotyl positions. In the canopy, δ(15)N was correlated fairly well between phloem and xylem saps. These variations in δ(15)N in transport saps can be attributed to nitrate reduction in leaves during the photoperiod as well as to (15)N-enriched glutamine acting as transport form of N. δ(15)N of the water soluble fraction of roots and leaves partially affected δ(15)N of phloem and xylems saps. δ(15)N patterns are likely the result of a complex set of interactions and N-fluxes between plant organs. Furthermore, the natural nitrogen isotope abundance in plant tissue is not constant during the diel course - a fact that needs to be taken into account when sampling for isotopic studies.
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Leaves of the mistletoe Viscum album (L.) show a high rate of transpiration, even when the host is under severe drought stress. The hypothesis that a strong control of ABA influx from the xylem sap of the host into the mistletoe prevents... more
Leaves of the mistletoe Viscum album (L.) show a high rate of transpiration, even when the host is under severe drought stress. The hypothesis that a strong control of ABA influx from the xylem sap of the host into the mistletoe prevents stomatal closure in mistletoe leaves was tested under the following conditions: sections of poplar twigs carrying a mistletoe were perfused with artificial xylem sap that contained different ABA concentrations and both transpiration and ABA levels were analysed in mistletoe leaves. Despite variation by a factor of 10(4), the ABA content of the host xylem did not affect ABA levels, leaf transpiration, CO(2) assimilation, WUE, or the degree of stomatal aperture in mistletoe leaves. These observations support the hypothesis of a strong control of ABA influx from the host of the xylem into the mistletoe, although degradation of ABA before it enters the mistletoe leaves cannot be excluded. This mechanism may ensure a water and nutritional status favourable for the mistletoe, even if the water status of the host is impaired. Despite the lack of short-term sensitivity of ABA levels in mistletoe leaves to even strong changes of ABA levels in the xylem sap of the host, ABA levels in mistletoe leaves were relatively high compared to ABA levels in the leaves of several tree species including poplar. Since significant transpiration of the mistletoe leaves was observed despite high ABA levels, a diminished sensitivity of the stomata of mistletoe leaves to ABA has to be concluded. The stomatal density of adaxial Viscum leaves of 89+/-23 stomata per mm is lower than those reported in a study performed at the end of the 19th century.
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... Andreas D. Peuke,; Rudolf Tischner,; Harald Lorenzen. Pflanzenphysiologisches Institut, University of Göttingen, Untere Karspüle 2, D-3400 Göttingen. Received 16 August 1985. ... Copyright © 1986Gustav Fischer Verlag, Stuttgart.... more
... Andreas D. Peuke,; Rudolf Tischner,; Harald Lorenzen. Pflanzenphysiologisches Institut, University of Göttingen, Untere Karspüle 2, D-3400 Göttingen. Received 16 August 1985. ... Copyright © 1986Gustav Fischer Verlag, Stuttgart. Published by Elsevier GmbH All rights reserved. ...
Research Interests: Membranes, Plant Biology, Biology, Starvation, Plant Physiology, and 10 morePl, ATPase, Membrane, Chlorella, Deficiency, Mes, CCR, Deficit, SDS PAGE, and Thallophyta
Research Interests: Botany, Chemistry, Nitrate, Nitrogen, Cutting, and 7 moreRhizosphere, Nutrient, Ammonium Nitrate, Ammonium, Salicaceae, Balsam, and Springer Ebooks
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Since the first description of phloem sap composition nearly 60 years ago, it is generally assumed that phloem sap does not contain nitrate and that there is little or no backflow of nitrate from shoots to roots. While it is true that... more
Since the first description of phloem sap composition nearly 60 years ago, it is generally assumed that phloem sap does not contain nitrate and that there is little or no backflow of nitrate from shoots to roots. While it is true that nitrate can occasionally be absent from phloem sap, there is now substantial evidence that phloem can carry nitrate and furthermore, transporters involved in nitrate redistribution to shoot sink organs and roots have been found. This raises the question of why nitrate may or may not be present in phloem sap, why its concentration is generally kept low, and whether plant shoot-root nutrient cycling also involves nitrate. We propose here that phloem sap nitrate is not only an essential component of plant nutritional signaling but also contributes to physical properties of phloem sap and as such, its concentration is controlled to ensure proper coordination of plant development and nutrient transport.
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Recent studies of transgenic poplars over-expressing the genes gsh1 and gsh2 encoding γ-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase, respectively, provided detailed information on regulation of GSH synthesis, enzymes... more
Recent studies of transgenic poplars over-expressing the genes gsh1 and gsh2 encoding γ-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase, respectively, provided detailed information on regulation of GSH synthesis, enzymes activities and mRNA expression. In this experiment, we studied quantitative parameters of leaves, assimilating tissues, cells and chloroplasts, mesophyll resistance for CO(2) diffusion, chlorophyll and carbohydrate content in wild-type poplar and transgenic plants over-expressing gsh1 in the cytosol after 3 years of growth in relatively clean (control) or heavy metal-contaminated soil in the field. Over-expression of gsh1 in the cytosol led to a twofold increase of intrafoliar GSH concentration and influenced the photosynthetic apparatus at different levels of organisation, i.e., leaves, photosynthetic cells and chloroplasts. At the control site, transgenic poplars had a twofold smaller total leaf area per plant and a 1.6-fold leaf area per leaf compared to wild-type controls. Annual aboveground biomass gain was reduced by 50% in the transgenic plants. The reduction of leaf area of the transformants was accompanied by a significant decline in total cell number per leaf, indicating suppression of cell division. Over-expression of γ-ECS in the cytosol also caused changes in mesophyll structure, i.e., a 20% decrease in cell and chloroplast number per leaf area, but also an enhanced volume share of chloroplasts and intercellular airspaces in the leaves. Transgenic and wild poplars did not exhibit differences in chlorophyll and carotenoid content of leaves, but transformants had 1.3-fold fewer soluble carbohydrates. Cultivation on contaminated soil caused a reduction of palisade cell volume and chloroplast number, both per cell and leaf area, in wild-type plants but not in transformants. Biomass accumulation of wild-type poplars decreased in contaminated soil by more than 30-fold, whereas transformants showed a twofold decrease compared to the control site. Thus, poplars over-expressing γ-ECS in the cytosol were more tolerant to heavy metal stress under field conditions than wild-type plants according to the parameters analysed. Correlation analysis revealed strong dependence of cell number per leaf area unit, chloroplast parameters and mesophyll resistance with the GSH level in poplar leaves.
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Cuttings of grapevine ( Vitis vinifera L. cv. Riesling clone B 68) grafted on SO4 (Selection Oppenheim No. 4) rootstocks were grown in pots with three different soils from Franconian vineyards derived from different geological formations... more
Cuttings of grapevine ( Vitis vinifera L. cv. Riesling clone B 68) grafted on SO4 (Selection Oppenheim No. 4) rootstocks were grown in pots with three different soils from Franconian vineyards derived from different geological formations (namely, Loess, Muschelkalk (shell lime), or Keuper). Additionally, the influence of N-fertilizer treatment was investigated. From the midrib of leaves six to eight of the sole shoot, xylem sap was collected simultaneously by pressurizing the rhizosphere during the vegetative growth phase. The chemical composition of xylem sap was determined and compared with that of the aqueous soil extract. In Muschelkalk soil, carbon, nitrogen, and calcium were present in the greatest concentrations. Sulfur, boron, magnesium, sodium, and potassium were greatest in Keuper, and the concentrations in Loess soil were intermediate. Aqueous extraction of the soils resulted in a two-fold greater concentration of total solutes in Keuper extract compared with Muschelkalk,...
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In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated... more
In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated capacity for phytochelatin production are compared with wildtype plants for the removal of heavy metals at different levels of contamination and under different climatic conditions. The studies are carried out with grey poplar (Populus tremula x P. alba), wildtype plants and plants overexpressing the gene for gamma-glutamylcysteine synthetase (gshI) from E. coli in the cytosol. The expression of this gene in poplar leads to two- to four-fold enhanced GSH concentrations in the leaves. In greenhouse experiments under controlled conditions these transgenic poplars showed a high potential for uptake and detoxification of heavy metals and pesticides. This capacity is evaluated in field experiments. Further aims of the project are to elucidate (a) the stabi...
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In a series of experiments with Ricinus communis, abscisic acid (ABA) concentrations in tissues and transport saps, its de novo biosynthesis, long-distance transport, and metabolism (degradation) were affected by nutritional conditions,... more
In a series of experiments with Ricinus communis, abscisic acid (ABA) concentrations in tissues and transport saps, its de novo biosynthesis, long-distance transport, and metabolism (degradation) were affected by nutritional conditions, nitrogen (N) source, and nutrient limitation, or salt stress. In the present study these data were statistically re-evaluated, and new correlations presented that underpin the importance of this universal phytohormone. The biggest differences in ABA concentration were observed in xylem sap. N source had the strongest effect; however, nutrient limitation (particularly phosphorus limitation) and salt also had significant effects. ABA was found in greater concentration in phloem sap compared with xylem sap; however, the effect of treatment on ABA concentration in phloem was lower. In the leaves, ABA concentration was most variable compared with the other tissues. This variation was only affected by the N source. In roots, ABA was significantly decreased...
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ABSTRACT
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... Andreas D. Peuke,; Rudolf Tischner,; Harald Lorenzen. Pflanzenphysiologisches Institut, University of Göttingen, Untere Karspüle 2, D-3400 Göttingen. Received 16 August 1985. ... Copyright © 1986Gustav Fischer Verlag, Stuttgart.... more
... Andreas D. Peuke,; Rudolf Tischner,; Harald Lorenzen. Pflanzenphysiologisches Institut, University of Göttingen, Untere Karspüle 2, D-3400 Göttingen. Received 16 August 1985. ... Copyright © 1986Gustav Fischer Verlag, Stuttgart. Published by Elsevier GmbH All rights reserved. ...
Research Interests: Membranes, Plant Biology, Plant Physiology, Pl, Membrane, and 6 moreDeficiency, Mes, CCR, Deficit, SDS PAGE, and Thallophyta
In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated... more
In the present paper actual trends in the use of transgenic trees for phytoremediation of contaminated soils are reviewed. In this context a current field trial in which transgenic poplars with enhanced GSH synthesis and hence elevated capacity for phytochelatin production are compared with wildtype plants for the removal of heavy metals at different levels of contamination and under different climatic conditions. The studies are carried out with grey poplar (Populus tremula x P. alba), wildtype plants and plants overexpressing the gene for gamma-glutamylcysteine synthetase (gshI) from E. coli in the cytosol. The expression of this gene in poplar leads to two- to four-fold enhanced GSH concentrations in the leaves. In greenhouse experiments under controlled conditions these transgenic poplars showed a high potential for uptake and detoxification of heavy metals and pesticides. This capacity is evaluated in field experiments. Further aims of the project are to elucidate (a) the stabi...
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Nitrogen isotope signatures in plants might give insights in the metabolism and allocation of nitrogen. To obtain a deeper understanding of the modifications of the nitrogen isotope signatures, we determined δ(15)N in transport saps and... more
Nitrogen isotope signatures in plants might give insights in the metabolism and allocation of nitrogen. To obtain a deeper understanding of the modifications of the nitrogen isotope signatures, we determined δ(15)N in transport saps and in different fractions of leaves, axes and roots during a diel course along the plant axis. The most significant diel variations were observed in xylem and phloem saps where δ(15)N was significantly higher during the day compared with during the night. However in xylem saps, this was observed only in the canopy, but not at the hypocotyl positions. In the canopy, δ(15)N was correlated fairly well between phloem and xylem saps. These variations in δ(15)N in transport saps can be attributed to nitrate reduction in leaves during the photoperiod as well as to (15)N-enriched glutamine acting as transport form of N. δ(15)N of the water soluble fraction of roots and leaves partially affected δ(15)N of phloem and xylems saps. δ(15)N patterns are likely the result of a complex set of interactions and N-fluxes between plant organs. Furthermore, the natural nitrogen isotope abundance in plant tissue is not constant during the diel course - a fact that needs to be taken into account when sampling for isotopic studies.
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ABSTRACT
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ABSTRACT
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ABSTRACT
... the wine in numerous ways, but mostly indirectly since grapes are supplied largely by the phloem during rip-ening [15]. Recent studies have highlighted the circula-tory nature of xylem and phloem [8,10,12,13,22,25,26]. In general, the... more
... the wine in numerous ways, but mostly indirectly since grapes are supplied largely by the phloem during rip-ening [15]. Recent studies have highlighted the circula-tory nature of xylem and phloem [8,10,12,13,22,25,26]. In general, the composition of xylem sap reflects both ...