The legume Rhizosphere

Dart, P. J.; Mercer, F. V.

doi:10.1007/bf00406359

Cited by 70 publications

(23 citation statements)

References 46 publications

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“…Polar attachment of bacteria to the roots of their respective hosts has been reported for R. japonicum (27), R. trnfolii (1 1, 22, 23, 28), and R. meliloti (8). (14).…”

Section: Discussionmentioning

confidence: 88%

Host Recognition in the Rhizobium-Soybean Symbiosis

Stacey¹,

Paau²,

Brill³

1980

Plant Physiol.

104

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(2,3,10,15,32). In the soybean system, a 120,000 dalton glycoprotein with specificity for D-galactose and N-acetyl-D-galactosamine binds specifically to infective strains of Rhizobium japonicum (2,3,(19)(20)(21). This lectin is found in seeds, leaves, stems, and roots of several varieties of Glycine max (23,26), although it appears to be absent or in very low quantity in a few varieties (26,29). Even with all of the evidence indicating that the lectin specifically binds to R. japonicum, there has been little direct evidence showing that this lectin actually binds the bacteria to the root. In only one legume system, that of white clover, has direct evidence been presented that a lectin binds the bacterium to the root (9, 10, 12).In that case, the lectin was localized at the site of infection. A hapten of the clover lectin, 2-deoxyglucose, specifically prevents binding of Rhizobium tr#folii to clover roots (9, 1 1). Similar studies to those performed with clover have not been done with soybeans chiefly because of the difficulty of adapting light microscopic studies to a large plant.Here, we overcame the difficulties of using a large plant such as G. max by using Glycine soja, a small-seeded soybean. The nodulation specificities of G. max and G. soja are very similar (6 The Rhizobium inoculum was grown in yeast extract-mannitol broth (30) at 30 C. The plant nutrient solution used (W. Leps, unpublished results) was as follows: 2 mm CaSO4.2H20; 5 mM K2SO4; 5 mm NaH2PO4. H20; 40 AM ethylene diaminetetraacetic acid ferric salt; 0.5 /IM CoCl2-6H20; 0.5 iM MgSO4.7H20; and I ml/l micronutrient solution (30). The pH of the PNS was adjusted to 7.0 with NaOH after autoclaving. Plants were grown at light intensity of 300 tiE/M2.* swith an 18-h photoperiod at 23-25C.Assay for Binding of Bacteria to Roots. G. soja seeds were sterilized by swirling them for 10 min in Clorox (The Clorox Co., Oakland, Calif.). The seeds were rinsed with sterile distilled H20 and scarified by soaking them in concentrated H2SO4 for 5 min. The seeds were rinsed with sterile H20 and soaked for an additional 10 min in 0.01 N HCI. After the HCI treatment, seeds were rinsed repeatedly with sterile H20 and germinated on sterile moist filter paper for 2 days. R. japonicum binding to G. soja roots was examined by using the slide-culture method of Fahraeus (13

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“…Polar attachment of bacteria to the roots of their respective hosts has been reported for R. japonicum (27), R. trnfolii (1 1, 22, 23, 28), and R. meliloti (8). (14).…”

Section: Discussionmentioning

confidence: 88%

Host Recognition in the Rhizobium-Soybean Symbiosis

Stacey¹,

Paau²,

Brill³

1980

Plant Physiol.

104

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“…Although a few direct observations have been made on the rhizosphere of seedlings (Starkey 1938;Lindford 1942;Jenny and Grossenbacher 1962;Dart and Mercer 1964) there are none reported on the ectotrophic mycorrhizosphere of Pinus radiata D. Don, the most widely used softwood in south-eastern Australia.…”

Section: Introductionmentioning

confidence: 99%

Observations on the Mycorrhizas of Forest Trees. II. The Rhizosphere of Pinus Radiata D. Don

Foster¹,

Marks²

1967

Aust. Jnl. Of Bio. Sci.

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SummaryTwo common mycorrhiza types of Pinus radiata were examined by light and electron microscopy. Large numbers of bacteria and fungal species other than those forming the mycorrhiza as well as diatoms were observed in the mycorrhizosphere. Different morphological types of bacteria were characteristic of different mycorrhizal types, and in some cases the bacteria were associated with lysed regions of the mantle. The distribution of the bacteria within the rhizosphere is discussed in relation to the clay minerals and the carbohydrate and polyphenol metabolisms of the host.Within the mantle and the Hartig net, the hyphae have a structure typical of basidiomycetes, but within the tannin layer the hyphae have an abnormal distorted appearance. This is correlated with changes in cytology and is construed as evidence of the production of polyphenols toxic to fungi.. A possible role of these polyphenols in the control of mycorrhizal associations by selective action on soil fungi entering the rhizosphere is discussed.

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“…Serial ing increasingly apparent that exogenous nitrogen has multiple and complex effects on both the establishment and functioning of nodules. The addition of nitrate, for example, seems to affect nodule function both at the level of rapid, reversible effects on nitrogen fixation and at the level of longer term, irreversible breakdown of tissue organization (9,10,14). Similarly, added nitrate has been reported to diminish the formation of new nodules by inhibiting attachment of rhizobia to the root (1 1), by inhibiting the formation of new root hairs (13,15), by preventing the induction ofroot hair curling by the bacteria (15), by blocking the initiation of infection threads (8, 13), and by limiting the development of nodule mass (19).…”

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confidence: 99%

Nitrate Induced Regulation of Nodule Formation in Soybean

Malik

Calvert²,

Bauer³

1987

Plant Physiol.

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Nodule formation was inhibited by exposing soybean plants to nitrate in plastic growth pouches. Exposure to 15 millimolar nitrate resulted in a 2.5-fold decrease in the number of nodules formed in the region of the primary root above the mark made at the time of inoculation to indicate the position of the root tip. Serial ing increasingly apparent that exogenous nitrogen has multiple and complex effects on both the establishment and functioning of nodules. The addition of nitrate, for example, seems to affect nodule function both at the level of rapid, reversible effects on nitrogen fixation and at the level of longer term, irreversible breakdown of tissue organization (9,10,14). Similarly, added nitrate has been reported to diminish the formation of new nodules by inhibiting attachment of rhizobia to the root (1 1), by inhibiting the formation of new root hairs (13,15), by preventing the induction ofroot hair curling by the bacteria (15), by blocking the initiation of infection threads (8, 13), and by limiting the development of nodule mass (19).The present work examines the effects of added nitrate on nodule formation by Bradyrhizobium japonicum in soybean. It is intended to provide background for later molecular analyses of regulatory mechanisms governing nodule formation in this host. We address the question of when nitrate must be present in order to inhibit nodulation, the question of whether nitrate must be in direct contact with affected root epidermal cells, and the question of whether nitrate inhibits infection initiation, infection development, or both. MATERIALS AND METHODSRhizobium Cultures. Bradyrhizobium japonicum strain USDA-I-110 ARS (azide, rifampicin, and streptomycin resistant) was a gift from Dr. D. Kuykendall, USDA, Beltsville, and has been used in all the studies described here except those involving the mutant strain NR 110. This mutant, which lacks nitrate reductase activity, is a derivative of wild-type strain 1 10 and was obtained from Dr. J. Streeter, Ohio State University. Cultures were kept freeze dried in ampules at -20°C for long-term storage. For short-term storage, B. japonicum suspensions from exponential phase cultures in a yeast-extract-mannitol-gluconate medium (2, 3) were washed and resuspended at 109 cell/ml in sterile deionized water and stored in this form at room temperature. The Bradyrhizobium strains tested, including 110 ARS, retain full viability and infectivity in this form for up to 1 month (7). Inoculum for each experiment was prepared by adding 0.2 ml of the water-stored suspension to 50 ml ofthe yeast extract medium and then allowing the culture to grow to early exponential phase (A at

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The legume Rhizosphere

Cited by 70 publications

References 46 publications

Host Recognition in the Rhizobium-Soybean Symbiosis

Host Recognition in the Rhizobium-Soybean Symbiosis

Observations on the Mycorrhizas of Forest Trees. II. The Rhizosphere of Pinus Radiata D. Don

Nitrate Induced Regulation of Nodule Formation in Soybean

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