Heteroauxin Production by Efficient and Inefficient Strains of Rhizobia

Georgi, Carl E.; Beguin, Albert E.

doi:10.1038/143025a0

Cited by 37 publications

(14 citation statements)

References 5 publications

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“…It is certainly not possible to explain the whole infection process only as an IAA effect (Kefford, Brockwell& Zwar, 1960). Such an explanation does not account for the marked specificity of rhizobial infection, since IAA is produced by almost all types of nodule bacteria, and also by Agrobacterium radiobacter which is unable to infect any leguminous plant (Georgi & Beguin, 1939).…”

Section: -3mentioning

confidence: 99%

The Role of Polygalacturonase in Root-Hair Invasion by Nodule Bacteria

Ljunggren¹,

Fåhræus²

1961

Journal of General Microbiology

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SUMMARYThe production of pol ygalacturonase in associations of nodule bacteria and seedlings of leguminous plants was investigated. Plants and bacteria were combined in the following ways : ( a ) different plant species were combined with infective strains (isolated from the same cross inoculation group) as well as non-infective ones (from foreign groups) ; ( b ) host plant species with different susceptibilities were combined with the same bacterial strain; ( c ) bacterial strains with different infectivities, as measured by the number of infection sites, were combined with the same host species; ( d ) clover strains which had lost their infectivity, as well as transformed and again infective subcultures of these strains, were tested on clover plants. The results indicate that infection of the seedlings was strongly correlated with the production of polygalacturonase. The conclusion is drawn that polygalacturonase plays an important part in the infection process. This function is thought to be a weakening of the cell wall of the root hair which would facilitate the bacterial invasion. The possible role also of indolyl-$-acetic acid in the infection process is discussed.

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Section: -3mentioning

confidence: 99%

The Role of Polygalacturonase in Root-Hair Invasion by Nodule Bacteria

Ljunggren¹,

Fåhræus²

1961

Journal of General Microbiology

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“…The possibility that the root hairs, in response to some stimulation by the bacteria, locally secrete an enzyme facilitating the penetration might also be considered. This idea seems to deserve some attention, especially since Neely, Ball, Hamner & Sell (1950) and Bryan & Newcomb (1954) have shown that the pectin methylesterase activity of some plant tissues is increased by auxins, for instance indole acetic acid, which is believed to be produced by nodule bacteria (Thornton & Nicol, 1936;Thimann, 1936;Chen, 1938;Georgi & Beguin, 1939). …”

Section: Iwechanisrn Of Entrymentioning

confidence: 99%

The Infection of Clover Root Hairs by Nodule Bacteria Studied by a Simple Glass Slide Technique

Fåhræus¹

1957

Microbiology

714

464

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SUMMARY: A simple glass slide technique has been devised for the continuous microscopical observation of growth and infection of root hairs of clover seedlings. The method involves an aseptic cultivation of seedlings on microscope slides which are partly immersed in a mineral salts medium. The roots are protected by a coverslip.By this procedure, the root hairs of white clover inoculated with nodule bacteria were studied. The earliest infection was observed to take place within 48 hr. of inoculation, on 4-day-old seedlings. In branched hairs the growth of the thread from a lateral branch towards the hair tip is tentatively explained as an effect of the position of the hair nucleus relative to the site of infection.The infection of leguminous plants by nodule bacteria has, as a rule, been studied with fixed and sectioned material. The first stages of this process may also be studied in vivo, but no suitable technique has yet been described for a continuous microscopical examination of these stages.A method for the study of growing root hairs (of wheat) was devised by Lundegkrdh (1946) and modified by Ekdahl(1953). In their work, a chamber containing flowing salt solution and resting on a microscope stage was employed. However, difficulties arise with this method if aseptic conditions are also necessary. The present author has therefore used a technique for the aseptic cultivation of young seedlings on microscope slides in a manner which permits periodic observations under the microscope of the growth and infection of individual root hairs. The arrangement also offers good conditions for photomicrography .The details of the method are as follows. METHODA nitrogen-free mineral solution of the following composition was prepared :CaCl,, 0.1 g.; MgSO4.7H,O, 0.12 g.; KH,PO,, 0.1 g.; Na,HPO,.ZH,O, 0.15 g.;Fe citrate, 0.005 g.; Mn, Cu, Zn, B, Mo traces; dist. water, 1000 ml.; pH 6.5 (after autoclaving).Portions (25 ml.) of this solution were distributed into large glass tubes (39 x 125 mm.). The tubes were plugged with cotton wool or covered with closely fitting glass caps (45 x 60 mm.) and were sterilized in the autoclave for 20 min. at 120" (15 lb./sq.in.). Microscope slides (26 x 75 mm.) and cover-slips (24 x 40 mm.) were sterilized by heating dry in Petri dishes, preferably only one slide and one cover-slip in each dish.

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“…Several auxins (1,4,5,6) and a gibberellin (8) have been found to be effective for inducing parthenocarpy in the Calimnvrna fig. None of the chemicals, however, has been adopted by the industry for commercial application because of the inferior quality of the figs produced.…”

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confidence: 99%

The interaction of nitrate and carbohydrates in rhizobial root nodule formation.

Raggio¹,

Raggio²,

Torrey³

1965

Plant Physiol.

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(10) devised a technique which allows axenic root culture in a system where the organic constituents of the synthetic medium are supplied to the base of the root while the rest of the organ grows into an inorganic medium. WVhen the latter medium was inoculated witlh the pl)oper rhizobia, nodules formed oln bean roots (11). Nodulation was inhibite(d if nitrate was added together Nvith the inorganiic salts suirroutndinlg the roots (11) but was promote(l if nlitrate was added to the organiic mloiety of the miiedi(im fed via the root bases (12).The purpose of the present paper is to report experiments in which the interaction of nitrate and carbohydrates on nodulationl wvas reexaminied usiig this isolated root systenl. Materials and MethodsFollowinig a modification (12) of the method of Raggio and Raggio (10). isolated roots of Pencil Pod black wax beans (Phaseolius vtlgaris L.) were cultivated axenically at 250. Roots from 4-day-old seedlings germinated aseptically were excised; the cut basal end of each root was introduced into a vial containing solidified agar nutrient medium. The vial and root were placed in a 1 1-cm petri dish containing sterile sand to which had been added liquid nutrient medium. The vial medium and the dish medium could thus be varied independently and the root, fed basally with a nutrient solution, could grow out into the sand in the dish containing another nutrient solution. Three days after excision the dishes were inoculated with a suspension in distilled water

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Heteroauxin Production by Efficient and Inefficient Strains of Rhizobia

Cited by 37 publications

References 5 publications

The Role of Polygalacturonase in Root-Hair Invasion by Nodule Bacteria

The Role of Polygalacturonase in Root-Hair Invasion by Nodule Bacteria

The Infection of Clover Root Hairs by Nodule Bacteria Studied by a Simple Glass Slide Technique

The interaction of nitrate and carbohydrates in rhizobial root nodule formation.

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