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  • 1
    Electronic Resource
    Electronic Resource
    Localization of phytosiderophore release and of iron uptake along intact barley roots (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 71 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Under iron deficiency the release of so-called phytosiderophores by roots of barley plants (Hordeum vulgare L. cv. Europa) was greater by a factor of 10 to 50 compared to iron-sufficient plants. This enhanced release occurred particularly in apical zones of the seminal roots and in the lateral root zones. Under iron deficiency, uptake rates for iron, supplied as FeIII phytosiderophore, increased by a factor of ca 5 as compared to iron-sufficient plants. This enhanced uptake rate for iron was also much more pronounced in apical than in basal root zones. In contrast, with supply of the synthetic iron chelate, FelII EDDHA (ferric diaminoethane-N, N-di-o-hydroxyphenyl acetic acid), the Fe deficiency-enhanced uptake rates for iron were only small and similar along the roots, except for the lateral root zones. The high selectivity of barley roots for uptake and translocation of FeIII phytosiderophores compared with FeIII EDDHA is reflected by the fact that, at the same external concentration (2 μM), rates of uptake and translocation of iron from FeIII phytosiderophores were between 100 (Fe-sufficient) and 1 000 times higher (Fe-deficient plants) than from FeIII EDDHA. The relatively high rates of uptake and particularly of translocation of iron supplied as FeIII EDDHA in the zone of lateral root formation strongly suggest an apoplastic pathway of radial transport of the synthetic iron chelate into the stele in this root zone.The results demonstrate that apical root zones are the main sites both for Fe deficiency-enhanced release of phytosiderophores and for uptake and translocation of iron supplied as FeIII phytosiderophores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb02861.x
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  • 2
    Electronic Resource
    Electronic Resource
    Are there connections between phenol metabolism, ascorbate metabolism and membrane integrity in leaves of boron-deficient sunflower plants? (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 104 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The influence of soluble phenol concentration and polyphenoloxidase activity in leaves of both B-deficient and B-sufficient sunflower plants (Helianthus annuus L. cv. Frankasol) on plasma membrane permeability was investigated, A study was also undertaken as to whether or not the incubation of B-deficient leaves in ascorbate- and calcium-containing solutions has a beneficial effect on plasma membrane integrity. Plants were cultivated under controlled environmental conditions with deficient and sufficient B supply and different light intensity to provoke changes in phenol metabolism. Analysis of membrane permeability (measured by potassium efflux), soluble phenol concentration and polyphenoloxidase (EC 1.10.3.1) activity of leaves showed that there was no correlation between these parameters. Furthermore, incubation in solutions containing ascorbate and calcium did not decrease the enhanced membrane permeability due to B deficiency, which could, however, be lowered by boric acid application. In summary, the results suggest that B does not maintain plasma membrane integrity by complexing phenols or inhibiting polyphenoloxidase activity, thereby preventing damage by oxygen free radicals. Ascorbate metabolism or calcium-related disorders seem also not to be involved. It is therefore likely that B has a direct function at the membrane, possibly by stimulating membrane-related enzymes, or in a structural role similar to that reported for the cell wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040325.x
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  • 3
    Electronic Resource
    Electronic Resource
    Boron compartmentation in roots of sunflower plants of different boron status: A study using the stable isotopes 10B and 11B adopting two independent approaches (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 113 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The intracellular compartmentation of boron (B) in roots of sunflower plants precultured with 100 μM B (high B) or 1 μM B (low B) was studied using two independent approaches. In the first approach, short-term efflux studies using the stable isotopes 11B and 10B were carried out. In roots of high B plants, the calculated concentrations of B (nmol gFW −1) were 52.6 in the cell wall, 7.5 in the vacuole, 27.1 in the cytosol and 48.0 in the free space. In roots of low B plants, the concentrations of B (nmol gFW −1) were 43.4 in the cell wall, 2.8 in the vacuole, 17.9 in the cytosol and almost zero in the free space. Although the B supply differed by a factor 100, the B concentrations in the cytosol and the vacuole of low B plants were 66 and 37% of the respective concentrations in high B plants. This suggests an additional role for B in plant metabolism, besides its function in the cell wall. In the second approach, root B pools (cell sap and water-insoluble residue) were determined for comparison, and found to be in good agreement with the results from the efflux study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1130307.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of boron starvation on boron compartmentation, and possibly hormone-mediated elongation growth and apical dominance of pea (Pisum sativum) plants (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 111 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two experiments were carried out to study the effects of boron (B) deficiency on 7-day-old pea plants for 6 or 9 days under controlled growth chamber conditions. Growth and apical dominance (AD) of the plants and their B concentration and compartmentation were followed throughout the starvation period. Additionally, auxin (indoleacetic acid, IAA) concentration in the shoot apex and polar transport from it were measured along with the cytokinin (CK) concentration in the shoot apex and the roots. The results demonstrate that during a 6-day B-deficiency period, B concentration in the water-insoluble residue of the roots was very stable and could not easily be reduced. In contrast, B concentration in the cell sap fraction was very sensitive to external B supply. Twelve hours after transferring the plants from B-sufficient to B-deficient solutions, the B concentration in root cell sap declined to half the concentration of the control plants. In addition, B concentration in the new aerial plant parts, which developed after the onset of the B-deficiency treatment, was extremely low. A decline in elongation growth could be observed as soon as about 4 days after the imposition of B deficiency. This preceded the first measurable growth of lateral buds (release from AD). Before the onset of these morphological changes, there was a considerable decline in CK concentration, accompanied by a dramatic decrease in IAA export out of the shoot apex, a decline in IAA concentration in the shoot apex and the roots and a reduced capacity for polar IAA-transport. These changes are discussed as possible reasons for the observed reduction in elongation growth and AD. These hormonal changes themselves are possibly the result of the decreased symplasmic B concentration, which in turn may be responsible for the reduced concentration in apical CKs. A sequence of events, which may be causally related, is suggested to explain the effects of B deficiency on the growth and AD of pea plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1110212.x
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  • 5
    Electronic Resource
    Electronic Resource
    Uptake kinetics of iron-phytosiderophores in two maize genotypes differing in iron efficiency (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Iron inefficiency in the maize (Zea mays L.) mutant ysl is caused by a defect in the uptake system for Fe-phytosiderophores. To characterize this defect further, the uptake kinetics of Fe-phytosiderophores in ysl was compared to the Fe-efficient maize cultivar Alice. Short-term uptake of 59Fe-labeled Fe-deoxymugineic acid (Fe-DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe-deficient plants followed Michaelis-Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe-phytosiderophores. The saturable component had similar Km (∼ 10 μM) in both genotypes. In contrast. Vmax was 5.5 μmol Fe-DMA g−1 dry weight [30 min]−1 in Alice, but only 0.6 μmol Fe-DMA g−1 dry weight [30 min]−1 in ysl. Uptake experiments with double-labeled 59Fe-[14C]DMA suggest that in both cultivars Fe-DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high-affinity and a low-affinity uptake system mediating Fe-phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency in ysl affected high-affected uptake and led to a decrease in activity and/or number of Fe-phytosiderophore transporters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb05107.x
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  • 6
    Electronic Resource
    Electronic Resource
    Different strategies for iron acquisition in higher plants (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 70 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb06137.x
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  • 7
    Electronic Resource
    Electronic Resource
    Is the release of phytosiderophores in zinc-deficient wheat plants a response to impaired iron utilization? (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of zinc nutritional status on the time course of phytosiderophore release, and uptake of iron and translocation of iron to the shoot, was studied in nutrient solution cultures for two cultivars of wheat (Triticum aestivum. cv. Aroona: T. durum, cv. Duratit) differing in their susceptibility to zinc deficiency. In the zinc-efficient cultivar Aroona, under zinc deficiency translocation of iron from roots to shoot was significantly decreased in 13- and 15-day-old plants, whereas release of phytosiderophores was enhanced when the plants were 16 days old. As zinc deficiency became more severe in older plains, translocation of iron to the shoot was further decreased and release of phytosiderophores was further enhanced. Resupplying zinc in nutrient solution to zinc-deficient plants significantly increased the translocation of iron to the shoot after 48 and 72 h. Concomitantly the release of phytosiderophores was repressed. The other cultivar Durati classified as zinc-inefficient in field observations differed from cv. Aroona by showing a lower rate of phytosiderophore release under Zinc deficiency, and a less impaired translocation of iron to the shoot. Foliar application of iron citrate to zinc-deficient Aroona plants repressed the release of phytosiderophores and increased iron concentrations in shoot and roots. Application of 55Fe to the leaves demonstrated that retranslocation of iron from the shoot to the roots was not affected by the zinc nutritional status. It is concluded that enhanced release of phytosiderophores in zinc-deficient wheat plants was induced primarily by impaired trans-location of iron lo the shoot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb08841.x
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  • 8
    Electronic Resource
    Electronic Resource
    Fusarinines and dimerum acid, mono- and dihydroxamate siderophores from Penicillium chrysogenum, improve iron utilization by strategy I and strategy II plants (2000)
    Springer
    BioMetals 13 (2000), S. 37-46 
    Details
    ISSN: 1572-8773
    Keywords: iron ; siderophores ; coprogen ; plant nutrition ; Penicillium chrysogenum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Cucumber, as a strategy I plant, and Maize as a strategy II plant, were cultivated in hydroponic culture in the presence of a ferrated siderophore mixture (1 μM) from a culture of Penicillium chrysogenumisolated from soil. The siderophore mixture significantly improved the iron status of these plants as measured by chlorophyll concentration to the same degree as a 100-fold higher FeEDTA supply. Analysis of the siderophore mixture from P. chrysogenum by HPLC and electrospray mass spectrometry revealed that besides the trihydroxamates, coprogen and ferricrocin, large amounts of dimerum acid and fusarinines were present which represent precursor siderophores or breakdown products of coprogen. In order to prove the iron donor properties of dimerum acid and fusarinines for plants, purified coprogen was hydrolyzed with ammonia and the hydrolysis products consisting of dimerum acid and fusarinine were used for iron uptake by cucumber and maize. In short term experiments radioactive iron uptake and translocation rates were determined using ferrioxamine B, coprogen and hydrolysis products of coprogen. While the trihydroxamates revealed negligible or intermediate iron uptake rates by both plant species, the fungal siderophore mixture and the ammoniacal hydrolysis products of coprogen showed high iron uptake, suggesting that dimerum acid and fusarinines are very efficient iron sources for plants. Iron reduction assays using cucumber roots or ascorbic acid also showed that iron bound to hydrolysis products of coprogen was more easily reduced compared to iron bound to trihydroxamates. Ligand exchange studies with epi-hydroxymugineic acid and EDTA showed that iron was easily exchanged between coprogen hydrolysis products and phytosiderophores or EDTA. The results indicate that coprogen hydrolysis products are an excellent source for Fe nutrition of plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009234612486
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  • 9
    Electronic Resource
    Electronic Resource
    Studies of iron transport by arbuscular mycorrhizal hyphae from soil to peanut and sorghum plants (1998)
    Springer
    Mycorrhiza 8 (1998), S. 35-39 
    Details
    ISSN: 1432-1890
    Keywords: Key words Arbuscular mycorrhiza ; Iron ; Peanut ; Phosphorus ; Sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The influence of an arbuscular mycorrhizal (AM) fungus on phosphorus (P) and iron (Fe) uptake of peanut (Arachis hypogea L.) and sorghum (Sorghum bicolor L.) plants was studied in a pot experiment under controlled environmental conditions. The plants were grown for 10 weeks in pots containing sterilised calcareous soil with two levels of Fe supply. The soil was inoculated with rhizosphere microorganisms only or with rhizosphere microorganisms together with an AM fungus (Glomus mosseae [Nicol. & Gerd.] Gerdemann & Trappe). An additional small soil compartment accessible to hyphae but not roots was added to each pot after 6 weeks of plant growth. Radiolabelled P and Fe were supplied to the hyphae compartment 2 weeks after addition of this compartment. After a further 2 weeks, plants were harvested and shoots were analysed for radiolabelled elements. In both plant species, P uptake from the labelled soil increased significantly more in shoots of mycorrhizal plants than non-mycorrhizal plants, thus confirming the well-known activity of the fungus in P uptake. Mycorrhizal inoculation had no significant influence on the concentration of labelled Fe in shoots of peanut plants. In contrast, 59Fe increased in shoots of mycorrhizal sorghum plants. The uptake of Fe from labelled soil by sorghum was particularly high under conditions producing a low Fe nutritional status of the plants. These results are preliminary evidence that hyphae of an arbuscular mycorrhizal fungus can mobilise and/or take up Fe from soil and translocate it to the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050208
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  • 10
    Electronic Resource
    Electronic Resource
    Physiological adaptations to phosphorus deficiency during proteoid root development in white lupin (1999)
    Springer
    Planta 208 (1999), S. 373-382 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Acid phosphatase ; Lupinus ; Organic acids ; Phosphorus (deficiency ; uptake) ; Root exudates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Release of large amounts of citric acid from specialized root clusters (proteoid roots) of phosphorus (P)-deficient white lupin (Lupinus albus L.) is an efficient strategy for chemical mobilization of sparingly available P sources in the rhizosphere. The present study demonstrates that increased accumulation and exudation of citric acid and a concomitant release of protons were predominantly restricted to mature root clusters in the later stages of P deficiency. Inhibition of citrate exudation by exogenous application of anion-channel blockers such as ethacrynic- and anthracene-9-carboxylic acids may indicate involvement of an anion channel. Phosphorus-deficiency-induced accumulation and subsequent exudation of citric acid seem to be a consequence of both increased biosynthesis and reduced metabolization of citric acid in the proteoid root tissue, indicated by increased in-vitro activity and enzyme protein levels of phosphoenolpyruvate carboxylase (EC 4.1.1.31), and reduced activity of aconitase (EC 4.2.1.3) and root respiration. Similar to citric acid, acid phosphatase, which is secreted by roots and involved in the mobilization of the organic soil P fraction, was released predominantly from proteoid roots of P-deficient plants. Also 33Pi uptake per unit root fresh-weight was increased by approximately 50% in juvenile and mature proteoid root clusters compared to apical segments of non-proteoid roots. Kinetic studies revealed a K m of 30.7 μM for Pi uptake of non-proteoid root apices in P-sufficient plants, versus K m values of 8.5–8.6 μM for non-proteoid and juvenile proteoid roots under P-deficient conditions, suggesting the induction of a high-affinity Pi-uptake system. Obviously, P-deficiency-induced adaptations of white lupin, involved in P acquisition and mobilization of sparingly available P sources, are predominantly confined to proteoid roots, and moreover to distinct stages during proteoid root development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050572
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