Nitrogenase activity (C2H2 reduction) of Azorhizobium in 2,4-D-induced root structures of wheat

Yu, D.; Kennedy, Ivan R.

doi:10.1016/0038-0717(95)98619-y

Cited by 11 publications

(9 citation statements)

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“…However, only low levels of nitrogenase activity were observed, and the addition of 2,4-D was generally detrimental to plant growth (Chen et al 1992 ;Yu & Kennedy 1995). Somewhat similar results have also been reported for rice inoculated with azorhizobia (Christiansen-Weniger 1996).…”

Section: Introductionsupporting

confidence: 67%

Endophytic establishment of Azorhizobium caulinodans in wheat

Sabry

Saleh

Batchelor

et al. 1997

Proc. R. Soc. Lond. B

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SUMMARYNitrogen fixing nodules are formed on the roots and stems of the tropical legume Sesbania rostrata by A orhi obium caulinodans as a result of crack entry invasion of emerging lateral roots. Advantage was taken of this invasion capability of A. caulinodans to determine whether inoculation of the non-legume wheat with A. caulinodans would result in the endophytic establishment of azorhizobia within wheat roots. Advantage was also taken of the oxygen tolerance of the nitrogenase of free-living azorhizobia to assess the extent to which the endophytic establishment of azorhizobia in wheat roots would provide a niche for nitrogen fixation of benefit to the plant. Wheat was inoculated with A. caulinodans and grown in pots under controlled conditions, without added growth regulators and without addition of fixed nitrogen. Microscopic examination of the short lateral roots of inoculated wheat showed invasion of azorhizobia between cells of the cortex, within the xylem and the root meristem. Acetylene reduction assays combined with analysis of tissue nitrogen levels indicated the likelihood that colonization led to nitrogenase activity. Inoculated wheat showed significant increases in dry weight and nitrogen content as compared with uninoculated controls. We discuss the extent to which this nitrogen fixation is likely to involve symbiotic nitrogen fixation, and we indicate the need for field trials to determine the extent to which inoculation of wheat with A. caulinodans will reduce the requirement for inputs of nitrogenous fertilizers.

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Section: Introductionsupporting

confidence: 67%

Endophytic establishment of Azorhizobium caulinodans in wheat

Sabry

Saleh

Batchelor

et al. 1997

Proc. R. Soc. Lond. B

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“…In forced associations of N # -fixing bacteria and plant roots, it appears that O # plays a crucial role in the ability of the bacteria to contribute nitrogen. It has been shown that even though 2,4-D increases the tolerance of Azorhizobium towards O # (Yu & Kennedy, 1995), nitrogenase activity is very low when values of O # exceed 5 kPa (ChristiansenWeniger, 1996). By contrast, the activity of nitrogenase in cyanobacteria, protected by heterocysts, remains high even at 20 kPa of O # , equivalent to that found in air (Fay, 1992).…”

Section: mentioning

confidence: 99%

“…One strategy has been to use the auxin 2,4-dichlorophenoxy-acetic acid (2,4-D) to induce the formation on roots of tumour-like growths, called para-nodules (Tchan & Kennedy, 1989). Paranodules have been created in wheat and shown to become infected with Azospirillum (Zeman et al, 1992 ;Katupitiya et al, 1995), Azorhizobium (Chen et al, 1992 ;Yu & Kennedy, 1995) and Derxia (Tchan & Zeman, 1995).…”

Section: Fixation Of Nitrogen (N #mentioning

confidence: 99%

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Colonization of wheat para‐nodules by the N₂‐fixing cyanobacterium Nostoc sp. strain 2S9B

Gantar

Elhai

1999

New Phytologist

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The treatment of wheat roots with 2,4-dichlorophenoxyacetic acid (2,4-D) led to the formation of tumour-like structures, para-nodules, which were readily colonized by cyanobacteria. The amount of cyanobacteria found on 2,4-D treated roots was 3n6 times higher than that found on untreated roots. Cyanobacteria penetrated the paranodules by migrating in between loosely arranged cells that covered their surfaces or by penetrating the space at the junction of root and para-nodule. In plants treated with 2,4-D and co-cultivated with cyanobacteria in medium without combined nitrogen, the rate of acetylene reduction was three times that seen in untreated but colonized roots. Addition of 2,4-D itself did not change the rate of acetylene reduction in free-living culture of Nostoc sp. strain 2S9B. In plants treated with 2,4-D and co-cultivated with Nostoc sp. strain 2S9B in medium without combined nitrogen the nitrogen content of roots but not shoots was significantly increased.

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“…However, Yu and Kennedy (1995) observed a nitrogenase activity in 2,4D induced root structures of Azorhizobium. Kennedy et al (1997) reported that 10 7 azospirilla in wheat seedlings are active in nitrogen fixation.…”

Section: Discussionmentioning

confidence: 98%

Paranodules and colonization of wheat roots by phytohormone producing bacteria in soil

Narula¹,

Deubel²,

Gans³

et al. 2006

Plant Soil Environ.

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Soil bacteria belonging to the genus Azotobacter, Pantoea and some unidentified soil isolates were tested in vitro for phytohormone production under laboratory and soil conditions. The German wheat variety Munk was inoculated by several soil bacteria with exogenously applied hormones (IAA, 2,4-D) and a flavonoid (naringenin) with a half of the amount of recommended doses of fertilizers under greenhouse conditions. Most of the soil bacteria tested were able to produce indole acetic acid (IAA), and stimulated a lateral root development and colonization by the addition of 2,4-D and IAA. A formation of paranodules on roots as a result of crack entry invasion was observed with 2,4-D as well as with IAA. We were able to reisolate the organism from the paranodules and could establish the same results. Analyses for root exudates and in vitro phytohormone production by various bacterial isolates were also carried out, revealing that 2,4-D can be replaced either by high IAA producing bacteria or by exogenous application of IAA. Bacterial survival in the rhizosphere as well as the root and shoot weight of wheat plants were positively affected also by the addition of IAA, 2,4-D and naringenin. A. brasilense (Sp7) partly due to the development of a protected niche. These paranodule structures derived from the induction of the initials of the lateral roots are quite dissimilar to root nodules particularly when colonized by non-symbiotic bacteria. Protoplasts of the bacteria (L-forms of Azotobacter, Pseudomonas syringae and Bacillus polymyxa) were suggested to have the ability to penetrate the cell wall and membrane structures of living plant cells and to colonize plant tissues (Cocking et al. 1990). Also some microorganisms colonize in the intercellular spaces as seen in apoplast of stem of sugarcane (Cocking 2003). Despite encouraging results with Azospirillum, Azotobacter etc., some controversy still exists about the mechanism of bacterial root interactions. Reports suggest that the colonization of these bacteria is caused by factors like N 2 fixation, siderophores, ammonia excretion, phytohormones (Lakshminarayana 1993) and antifungal properties etc. (Verma et al. 2001), collectively enhancing the root proliferation, increase in the lateral roots and root hair formation. Dobbelaere et al. (1999) suggested that plant growth substances are one of the key factors observed in plant growth promotion. Tien et al. (1979) reported that the morphological changes due to bacterial inoculations can be mimicked by applying a combination of plant growth substances.Keeping all these factors in mind, we made an attempt to screen different soil bacteria for the production of various phytohormones, their colonization on German winter wheat (var. Munk) with or without exogenously applied natural and synthetic plant hormones and the concomitant changes in root morphology or formation of paranodules under controlled greenhouse conditions in addition to plant growth parameters. Natural hormone like IAA, synthetic-2,4-D (2,4-dichlorophen...

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Nitrogenase activity (C2H2 reduction) of Azorhizobium in 2,4-D-induced root structures of wheat

Cited by 11 publications

References 9 publications

Endophytic establishment of Azorhizobium caulinodans in wheat

Endophytic establishment of Azorhizobium caulinodans in wheat

Colonization of wheat para‐nodules by the N₂‐fixing cyanobacterium Nostoc sp. strain 2S9B

Paranodules and colonization of wheat roots by phytohormone producing bacteria in soil

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Nitrogenase activity (C2H2 reduction) of Azorhizobium in 2,4-D-induced root structures of wheat

Cited by 11 publications

References 9 publications

Endophytic establishment of Azorhizobium caulinodans in wheat

Endophytic establishment of Azorhizobium caulinodans in wheat

Colonization of wheat para‐nodules by the N2‐fixing cyanobacterium Nostoc sp. strain 2S9B

Paranodules and colonization of wheat roots by phytohormone producing bacteria in soil

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Colonization of wheat para‐nodules by the N₂‐fixing cyanobacterium Nostoc sp. strain 2S9B