ISSN:
1432-0789
Schlagwort(e):
Azospirillum brasilense
;
15N-isotope enrichment
;
Nitrogen fixation
;
Auxine
;
2,4-dichlorphenoxy acetic acid
;
3,5-dichlor-phenoxy acetic acid
;
Acetylene reduction assay
;
Wheat
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Geologie und Paläontologie
,
Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
Notizen:
Summary Wheat seedlings, treated with the auxine 2,4-dichlor-phenoxy acetic acid (2,4-D) during germination developed only a residual root system. Root elongation was extremely restricted and root tips were deformed to thick club-shaped tumours. When 2,4-D was added in a later stage of plant growth the plants developed additional nodule-like knots along primary roots. Root and shoot dry-matter production was slightly repressed in all 2,4-D treatments and N translocation from roots to shoots was repressed as well. When transferred to an auxine-free growth medium, the 2,4-D-affected roots were not capable of complete recovery. In plants inoculated gnotobiotically with Azospirillum brasilense, either with the wild type or with the NH 4 + -excreting mutant strain C3, a 2,4-D addition increased rhizosphere acetylene-reduction activity at pO2 1.5 kPa. The O2 sensitivity of root-associated nitrogenase activity tended to be reduced. The number of root-colonizing bacteria, at approximately 108 colony-forming units (cfu) per g dry root, was similar in the 2,4-D treatments and untreated controls. Plant treatment with high concentrations of the chemical isomer 3,5-dichlor-phenoxy acetic acid (3,5-D) did not have comparable effects, either on plant development or on rhizosphere-associated nitrogenase activity. Root-tumour tissue inhabited by A. brasilense showed purple staining when subjected to a tetrazolium chloride solution, which may indicate intensive local nitrogenase activity in this tissue. Exposed to an 15N2-enriched atmosphere, plants treated with 2,4-D and with A. brasilense incorporated significantly higher amounts of 15N than untreated controls. In all cases the highest values of 15N enrichment were found following inoculation with the NH 4 + -excreting mutant strain C3.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00336274
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