EFFET DU SOUFRE ET DE L’AZOTE SUR LA FIXATION SYMBIOTIQUE D’AZOTE CHEZ LES PLANTULES DE LUZERNE (Medicago Sativa L.)

The effect of the addition of sulphur and nitrogen on the aerial mass, root mass, nodulation and nitrogenase activity was studied on alfalfa cv. Saranac seedlings inoculated with a very efficient strain of Rhizobium meliloti. The aerial mass, root mass and a nodulation index increase with the addition of increasing concentrations of nitrogen and sulphur. The rate of increase of aerial mass and the nodulation index with sulphur are not constant over the range of the concentrations studied. Sulphur and nitrogen appeared to have a very important multiplicative effect on aerial mass and root mass. In the absence of sulphur, nitrogen did not affect nitrogenase activity. The aerial mass and the nodulation index are strongly correlated to the root mass and nitrogenase activity. However, nitrogenase activity and the root mass were not significantly correlated.

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NITROGENASE ACTIVITY OF ALFALFA GROWN ALONE AND IN MIXTURE WITH GRASS UNDER GREENHOUSE CONDITIONS

Canadian Journal of Plant Science ◽

10.4141/cjps85-102 ◽

1985 ◽

Vol 65 (3) ◽

pp. 787-791

Author(s):

H. A. BURITY ◽

B. E. COULMAN ◽

M. A. FARIS

Keyword(s):

Medicago Sativa ◽

Nitrogenase Activity ◽

Dactylis Glomerata ◽

Phleum Pratense ◽

Bromus Inermis ◽

Smooth Bromegrass ◽

Medicago Sativa L ◽

Dactylis Glomerata L ◽

Phleum Pratense L ◽

Nodule Tissue

A greenhouse experiment has shown that total nitrogenase activity of alfalfa (Medicago sativa L.) is not significantly affected when grown in association with timothy (Phleum pratense L.), smooth bromegrass (Bromus inermis Leyss) or orchardgrass (Dactylis glomerata L.) except after initial harvest when decreased alfalfa activity was associated with smooth bromegrass or orchardgrass. It was concluded that mixed cultures of alfalfa with timothy, smooth bromegrass or orchardgrass have no effect on alfalfa N2 fixation. The results also suggest the occurrence of N transference from alfalfa to associated grasses. It is speculated that this transfer is not primarily due to the death of roots and nodule tissue (after harvest), but involves some degree of N excretion during the period before initial harvest.Key words: Alfalfa-grass mixtures, N2-fixation, nodule activity, N-transference

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Kinetics of first-cutting regrowth of alfalfa plants and nitrogenase activity in a controlled environment with and without added nitrate

Canadian Journal of Botany ◽

10.1139/b83-264 ◽

1983 ◽

Vol 61 (9) ◽

pp. 2405-2409 ◽

Cited By ~ 6

Author(s):

F. D. H. Macdowall

Keyword(s):

Dry Matter ◽

Rhizobium Meliloti ◽

Nitrogenase Activity ◽

Radical Change ◽

N Nutrition ◽

Meliloti Strain ◽

Medicago Sativa L ◽

Reducing Activity ◽

Acetylene Reducing Activity ◽

Kinetics Of

Seedlings of Medicago sativa L. cv. Algonquin were grown in vermiculite and nodulated by Rhizobium meliloti strain 102F70 at two lower levels of N, until flowering when the tops were cut off to leave about 10% shoot stubble. Residual shoot dry matter immediately resumed first-order growth and maintained it throughout regrowth to second flowering. The rate constants of shoot regrowth were 34% lower (at 15 mM NO3−), 25% lower (at 1.5 mM NO3− symbiotically), or 220% higher (at zero NO3− symbiotically) than the values for 1 to 4-week-old seedlings, which indicated a radical change in physiology. Root dry matter resumed exponential growth after a 7-day recession and its recovery and yields were independent of N nutrition. The most pronounced minima occurred in the acetylene-reducing activity of nitrogenase, the kinetics of which paralleled root dry matter except that its redevelopment stopped after two-thirds of the regrowth time. The rate coefficient for the redevelopment of nitrogenase activity equalled that for its development during the seedling stage, which suggested unchanged limitations on that process until its redevelopment stopped.

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A multiple-trait breeding program for improving the symbiosis for N2 fixation between Medicago sativa L. and Rhizobium meliloti

Breeding Legumes for Enhanced Symbiotic Nitrogen Fixation ◽

10.1007/978-94-009-5077-1_3 ◽

1984 ◽

pp. 31-42 ◽

Cited By ~ 1

Author(s):

D. K. Barnes ◽

G. H. Heichel ◽

C. P. Vance ◽

W. R. Ellis

Keyword(s):

Medicago Sativa ◽

N2 Fixation ◽

Rhizobium Meliloti ◽

Breeding Program ◽

Multiple Trait ◽

Medicago Sativa L

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A rapid screening method for Rhizobium meliloti symbiotic nitrogenase activity

Canadian Journal of Microbiology ◽

10.1139/m82-037 ◽

1982 ◽

Vol 28 (2) ◽

pp. 265-268 ◽

Cited By ~ 10

Author(s):

J. C. Sirois ◽

E. A. Peterson

Keyword(s):

Positive Relationship ◽

Rhizobium Meliloti ◽

Nitrogenase Activity ◽

Screening Method ◽

Dry Weight ◽

Rapid Screening ◽

Experimental Conditions ◽

Intact Plants ◽

Medicago Sativa L ◽

Rapid Screening Method

A method for screening Rhizobium meliloti isolates for their symbiotic nitrogenase activity with alfalfa (Medicago sativa L.) cv. Apollo is described. The nitrogenase activity of each isolate is assessed by measuring the reduction of acetylene (C2H2) to ethylene (C2H4) by 50 intact plants grown in 10 plastic pouches for 2 weeks. The method is rapid, sensitive, reproducible, and accurate enough to differentiate 29 Rhizobium isolates and 5 authentic strains into 13 subsets. Under the experimental conditions used, nodulation occurred within 5 days of inoculation and there was a significant positive relationship between the nitrogenase activity of those isolates which reduced more than 60 nmol C2H2∙plant−1∙h−1 and the dry weight of the shoots of the nodulated plants in 2 weeks of growth.

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