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  • 1
    Electronic Resource
    Electronic Resource
    Acid phosphomonoesterase and phytase activities of wheat (Triticum aestivum L.) roots and utilization of organic phosphorus substrates by seedlings grown in sterile culture (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Wheat seedlings exhibited a differential ability to utilize P from a range of organic P substrates when grown in agar culture under sterile conditions. Plants showed limited ability to obtain P from inositol hexaphosphate (IHP), whereas other monoester substrates such as glucose 1-phosphate (G1P), were equivalent sources of P for plant growth as compared with inorganic phosphate (Pi). Poor utilization of IHP was exemplified by significantly lower rates of dry matter accumulation and reduced P content of tissues, which were generally not significantly different to control plants that were grown in the absence of added P. The inability of wheat seedlings to obtain P from IHP was not associated with poor substrate availability but was due to either insufficient root phytase activity or inappropriate localization of phytase within root tissues. Phytase activities of 4 and 24 mU g−1 root fresh weight (FW) were determined for crude root extracts prepared from plants that were grown with either adequate P or under deficient conditions, respectively. Similar levels of phytase activity (approximately 12 mU g−1 FW) were observed in assays using intact roots, although no secreted activity was detected. By comparison, a secreted acid phosphomonoesterase activity was observed, and activities of between 466 and 1029 mU phosphomonoesterase g−1 root FW were measured for intact roots. On the basis of the differences in enzyme activity, and the observed differences in the ability of wheat seedlings to utilize G1P and IHP, it is evident that low intrinsic levels of phytase activity in wheat roots is a critical factor that limits the ability of wheat to obtain P from phytate when supplied in agar under non-limiting conditions. This hypothesis was further supported by the observation that the ability of wheat to obtain P from IHP was significantly improved when the seedlings were inoculated with a soil bacterium (Pseudomonas sp. strain CCAR59) that possesses phytase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00557.x
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of transgenic Trifolium subterraneum L. which expresses phyA and releases extracellular phytase: growth and P nutrition in laboratory media and soil (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Transgenic Trifolium subterraneum expressing a phytase gene (phyA) from Aspergillus niger were generated. Five independently transformed lines showed an average 77-fold increase in exuded phytase activity in comparison with null segregant and wild-type controls. Unlike other phosphatases, exuded phytase activity was unaffected by P supply, verifying the constitutive expression of phyA. Transgenic T. subterraneum grown in agar with P supplied as phytate, took up 1.3- to 3.6-fold more P than controls and had equivalent P uptake to plants supplied with orthophosphate. This unique phenotype was compromised when the plants were grown in soil. None of the five lines showed increased shoot biomass or total P uptake in an unfertilized, low-P soil taken from under permanent pasture. With addition of P, one of the five transgenic lines had consistently greater P nutrition compared with control plants. Despite variable growth and P nutrition responses, P uptake per root length was on average greater for transgenic lines. Exudation of phytase by transgenic T. subterraneum allowed utilization of P from phytate in non-sorbing, sterile laboratory media, but was less effective when plants were grown in soil. Release of extracellular phytase is therefore not the only requirement for the acquisition of P from endogenous soil phytate by plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01225.x
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  • 3
    Electronic Resource
    Electronic Resource
    Symbiotic effectiveness of Bradyrhizobium strains isolated from Parasponia and tropical legumes on Parasponia host species (1990)
    Springer
    Plant and soil 124 (1990), S. 117-126 
    Details
    ISSN: 1573-5036
    Keywords: Bradyrhizobium ; effectiveness ; groups ; incompatible ; tropical legumes ; nitrogen fixation ; nodulation ; non-legume ; Parasponia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The symbiotic effectiveness of Bradyrhizobium strains isolated from three species of Parasponia and from legumes were compared on Parasponia grown in Leonard-jars. Effectiveness of each symbiotic association was estimated from dry weight and total nitrogen of shoots and nodules of plants grown on medium free of combined nitrogen. Twenty strains isolated from three species of Parasponia were found to vary in their effectiveness on P. andersonii, the least effective fixing one fifth of the nitrogen of the most effective strains. The outcome of the symbiosis was not associated with the host source of the test strain. P. andersonii, P. rugosa and P. rigida responded differently to a selection of seven strains of Parasponia Bradyrhizobium; some strains were either ineffective or fully effective on each host, while others varied in their symbiotic performance. P. andersonii fixed significantly (P 〈 0.001) larger quantities of nitrogen than either P. rugosa or P. rigida with p. rigida being the least effective. In contrast to Bradyrhizobium strains from Parasponia spp. which formed nodules rapidly (within 11–20 days), nine strains isolated from legumes required between 25 and 74 days to form partially effective nodules. The thre Parasponia species formed relatively large quantities of nodule tissue relative to the amount of nitrogen fixed and shoot dry matter produced. The Bradyrhizobium isolated from Parasponia plants growing in Papua New Guinea soils could be grouped together on the basis of their infection characteristics on Parasponia and legumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010939
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  • 4
    Electronic Resource
    Electronic Resource
    Biology of theParasponia-Bradyrhizobium symbiosis (1988)
    Springer
    Plant and soil 110 (1988), S. 177-185 
    Details
    ISSN: 1573-5036
    Keywords: Bradyrhizobium ; competition ; haemoglobin ; non-legume ; Parasponia ; symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Parasponia remains the only non-legume known to nodulate withRhizobium/Bradyrhizobium. It is a pioneer plant that is capable of rapid growth and fixing large quantities of nitrogen. In addition to its high agronomic potential, the symbiosis offers the scientist the unique opportunity of studying differences at the molecular level of both partners, and to investigate any possible extension of the symbiosis to other non-legumes of importance. Haemoglobin has been found in the nodule tissue ofParasponia and other nodulated non-legumes and the gene for it has been found and expressed in non-nodulating plants such asTrema tomentosa andCeltis australis. Bradyrhizobium strains isolated from species ofParasponia growing in Papua New Guinea form a group that are more specific in their host requirements thanBradyrhizobium strains from tropical legumes from the same area. They do not effectively nodulate (except CP283) tropical legumes, andParasponia is not readily nodulated withRhizobium andBradyrhizobium strains from legumes. The effectiveness of the symbiosis is influenced by host species, theBradyrhizobium strain and the environment.Parasponia andersonii forms a more effective symbiosis than the other species tested. In competition studies with strains from legumes, isolates fromParasponia always dominate in nodules onParasponia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02226797
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  • 5
    Electronic Resource
    Electronic Resource
    Nodulation of Trifolium repens with modified Bradyrhizobium and the nodulation of Parasponia with Rhizobium leguminosarum biovar trifolii (1990)
    Springer
    Plant and soil 125 (1990), S. 49-61 
    Details
    ISSN: 1573-5036
    Keywords: cross-inoculation ; dual occupancy ; modified Bradyrhizobium ; nodulation ; Parasponia ; Rhizobium ; rhizosphere ; specificity ; Trifolium repens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Thirty one strains of Rhizobium leguminosarum biovar trifolii isolated from the North and South American continents, New Guinea, USSR, Turkey and Australia, nodulated P. andersonii ineffectively when grown in plant growth tubes and in Leonard jars. Nodules were slow to form, sometimes taking over 100 days. Reisolates of R. leguminosarum biovar trifolii from P. andersonii nodulated Trifolium repens and their identity was confirmed using serological techniques. Dual occupation of nodules by Rhizobium and Bradyrhizobium in P. andersonii is reported. The reduced effectiveness of the Bradyrhizobium symbiosis depended on the relative numbers of Rhizobium occupants in this dual system. R. leguminosarum biovar trifolii and Bradyrhizobium strains from Parasponia were able to co-exist in nodules on P. andersonii and maintain similar populations in the rhizosphere and on culture media. Bradyrhizobium strains, separated from R. leguminosarum biovar trifolii, were able to initiate and form nodule-like structures on T. repens. Bradyrhizobium bacteria were identified as the sole occupants of the cells of the nodule-like structures on Trifolium repens using an immunogold labelling technique applied to ultrathin sectins. The re-isolates of Bradyrhizobium obtained from these nodule-like structures on T. repens were able to effectively nodulate P. andersonii.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010743
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of nodular structures on the non-legumes Brassica napus, B. campestris, B. juncea and Arabidopsis thaliana with Bradyrhizobium and Rhizobium isolated from Parasponia spp. or legumes grown in tropical soils (1995)
    Springer
    Plant and soil 172 (1995), S. 207-219 
    Details
    ISSN: 1573-5036
    Keywords: Bradyrhizobium ; Brassica ; infection ; nodulation ; Rhizobium ; toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Strains of Bradyrhizobium formed nodule-like structures on Arabidopsis and species of Brassica in pots with sandvermiculite and in glass tubes on a nitrogen-free mineral salts agar. Broad-host-range Rhizobium strains NGR234 from Lablab purpureus and NGR76 from Phaseolus vulgaris formed similar nodule-like structures on Brassica spp. The size of these structures on plants in pots were large, often reaching 10 mm in diameter. The frequency of inoculated Brassica plants in pots with nodule-like structures was 25–50%, depending on the inoculum strain. The inheritable nature of factors involved in the formation of the nodule-like structures was demonstrated when the structures occurred on 100% of inoculated B. napus seedlings derived from plants with the nodule-like structures. Nodule-like structures occurred without, but not with, the application of a cellulase-pectolyase-PEG treatment to the roots. Attempts to isolate Bradyrhizobium or Rhizobium from the nodule-like structures failed. Internal infection of these structures could not be detected using either the light or electron microscope. The inoculum strains of root-nodule bacteria were detected in high numbers in the rhizosphere of plants 5 months after inoculation. On agar plates bacterial colonies could be seen, with undiminished growth, over the surface of the agar extending to the root surface. However, ground root tissue of Brassica was toxic to Bradyrhizobium strains. This suggested that Bradyrhizobium strains would not survive after infecting the roots of Brassica spp. Nitrogen fixation was associated with high rhizosphere populations of Azospirillum and not with Bradyrhizobium induced nodule structures of Brassica spp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011323
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