Nondestructive acetylene reduction assays of intact nitrogen-fixing systems in soil. Vaughn, C. E. Master's thesis, Univ. Calif. Davis, Davis, CA, 1974. abstract bibtex Abstract: A method for short-duration acetylene reduction assays of nitrogen fixation by intact nitrogenase systems in soil was developed. Undisturbed cultures were grown in 2.4-liter polyethylene pots. The pots were sealed, the cultures exposed to an air-acetylene atmosphere, and assayed for ethylene production. No lag period was observed in the ethylene production rates of subclover plants (Trifolium subterraneum) if the gases were mixed during an incubation by pumping a syringe inserted through a rubber serum stopper fitted in the bottom of the pot. Acetylene saturated the nitrogenase systems of excised subclover nodules at a pC2H2 of 0.10 atm, but for ease of handling the standard assays were conducted at a pC2H2 of 0.05 atm. Ethylene production at saturating acetylene levels was calculated with the Michaelis-Menten equation. Diurnal variation in nitrogenase activity was large so a mean daily activity value was used in calculating daily ethylene production. Successive biweekly assays of 60-minute duration were conducted on 7 species of annual clovers during complete growth and maturation cycles. There was a significant linear relationship between seasonal ethylene production and both dry matter production and nitrogen uptake. An average of approximately 4.5 moles of ethylene were produced per mole of nitrogen fixed. Ethylene production during a 4-month period by free-living soil organisms in the rhizosphere of the annual grass soft chess (Bromus mollis) was significantly and inversely related to the amount of fertilizer N applied. Ethylene production was significantly higher in the grass rhizosphere than in comparable fallow soils, except where 100 ppm N was applied to the grass cultures.
@mastersthesis{vaughn_nondestructive_1974-1,
address = {Davis, CA},
title = {Nondestructive acetylene reduction assays of intact nitrogen-fixing systems in soil},
shorttitle = {Nondestructive acetylene reduction assays of intact nitrogen-fixing systems in soil},
abstract = {Abstract: A method for short-duration acetylene reduction assays of nitrogen fixation by intact nitrogenase systems in soil was developed. Undisturbed cultures were grown in 2.4-liter polyethylene pots. The pots were sealed, the cultures exposed to an air-acetylene atmosphere, and assayed for ethylene production. No lag period was observed in the ethylene production rates of subclover plants (Trifolium subterraneum) if the gases were mixed during an incubation by pumping a syringe inserted through a rubber serum stopper fitted in the bottom of the pot. Acetylene saturated the nitrogenase systems of excised subclover nodules at a pC2H2 of 0.10 atm, but for ease of handling the standard assays were conducted at a pC2H2 of 0.05 atm. Ethylene production at saturating acetylene levels was calculated with the Michaelis-Menten equation. Diurnal variation in nitrogenase activity was large so a mean daily activity value was used in calculating daily ethylene production. Successive biweekly assays of 60-minute duration were conducted on 7 species of annual clovers during complete growth and maturation cycles. There was a significant linear relationship between seasonal ethylene production and both dry matter production and nitrogen uptake. An average of approximately 4.5 moles of ethylene were produced per mole of nitrogen fixed. Ethylene production during a 4-month period by free-living soil organisms in the rhizosphere of the annual grass soft chess (Bromus mollis) was significantly and inversely related to the amount of fertilizer N applied. Ethylene production was significantly higher in the grass rhizosphere than in comparable fallow soils, except where 100 ppm N was applied to the grass cultures.},
school = {Univ. Calif. Davis},
author = {Vaughn, Charles E.},
year = {1974},
keywords = {1974, Bromus mollis, Trifolium subterraneum, Vaughn, C. E., acetylene reduction assays, clover, subterranean, clovers, annual, grass, annual, nitrogen fixation, estimation, soft chess, subclover}
}
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The pots were sealed, the cultures exposed to an air-acetylene atmosphere, and assayed for ethylene production. No lag period was observed in the ethylene production rates of subclover plants (Trifolium subterraneum) if the gases were mixed during an incubation by pumping a syringe inserted through a rubber serum stopper fitted in the bottom of the pot. Acetylene saturated the nitrogenase systems of excised subclover nodules at a pC2H2 of 0.10 atm, but for ease of handling the standard assays were conducted at a pC2H2 of 0.05 atm. Ethylene production at saturating acetylene levels was calculated with the Michaelis-Menten equation. Diurnal variation in nitrogenase activity was large so a mean daily activity value was used in calculating daily ethylene production. Successive biweekly assays of 60-minute duration were conducted on 7 species of annual clovers during complete growth and maturation cycles. There was a significant linear relationship between seasonal ethylene production and both dry matter production and nitrogen uptake. An average of approximately 4.5 moles of ethylene were produced per mole of nitrogen fixed. Ethylene production during a 4-month period by free-living soil organisms in the rhizosphere of the annual grass soft chess (Bromus mollis) was significantly and inversely related to the amount of fertilizer N applied. Ethylene production was significantly higher in the grass rhizosphere than in comparable fallow soils, except where 100 ppm N was applied to the grass cultures.","school":"Univ. Calif. Davis","author":[{"propositions":[],"lastnames":["Vaughn"],"firstnames":["Charles","E."],"suffixes":[]}],"year":"1974","keywords":"1974, Bromus mollis, Trifolium subterraneum, Vaughn, C. 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