This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Vance, C. P. Articles by Maxwell, C. A. Search for Related Content PubMed PubMed Citation Articles by Vance, C. P. Articles by Maxwell, C. A. Agricola Articles by Vance, C. P. Articles by Maxwell, C. A.

Articles

Alfalfa Root Nodule Carbon Dioxide Fixation ^1,2

I. Association with Nitrogen Fixation and Incorporation into Amino Acids

United States Department of Agriculture, Science and Education Administration, Agricultural Research Service, The University of Minnesota, St. Paul, Minnesota 55108, Department of Agronomy and Plant Genetics, The University of Minnesota, St. Paul, Minnesota 55108

In vivo CO₂ fixation activity and in vitro phosphoenolpyruvate carboxylase activity were demonstrated in effective and ineffective nodules of alfalfa (Medicago sativa L.) and in the nodules of four other legume species. Phosphoenolpyruvate carboxylase activity was greatly reduced in nodules from both host and bacterially conditioned ineffective alfalfa nodules as compared to effective alfalfa nodules.

Forage harvest and nitrate application reduced both in vivo and in vitro CO₂ fixation activity. By day 11, forage harvest resulted in a 42% decline in in vitro nodule phosphoenolpyruvate carboxylase activity while treatment with either 40 or 80 kilograms nitrogen per hectare reduced activity by 65%. In vitro specific activity of phosphoenolpyruvate carboxylase and glutamate synthase were positively correlated with each other and both were positively correlated with acetylene reduction activity.

The distribution of radioactivity in the nodules of control plants (unharvested, 0 kilograms nitrogen per hectare) averaged 73% into the organic acid and 27% into the amino acid fraction. In nodules from harvested plants treated with nitrate, near equal distribution of radioactivity was observed in the organic acid (52%) and amino acid (48%) fractions by day 8. Recovery to control distribution occurred only in those nodules whose in vitro phosphoenolpyruvate carboxylase activity recovered.

The results demonstrate that CO₂ fixation is correlated with nitrogen fixation in alfalfa nodules. The maximum rate of CO₂ fixation for attached and detached alfalfa nodules at low CO₂ concentrations (0.13-0.38% CO₂) were 18.3 and 4.9 nanomoles per hour per milligram dry weight, respectively. Nodule CO₂ fixation was estimated to provide 25% of the carbon required for assimilation of symbiotically fixed nitrogen in alfalfa.

² Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by either the United States Department of Agriculture or approval to the exclusion of other products that may also be suitable.

This article has been cited by other articles:

				J. M.-F. Johnson, R. R. Allmaras, and D. C. Reicosky Estimating Source Carbon from Crop Residues, Roots and Rhizodeposits Using the National Grain-Yield Database Agron. J., April 11, 2006; 98(3): 622 - 636. [Abstract] [Full Text] [PDF]

				A. F. López-Millán, F. Morales, S. Andaluz, Y. Gogorcena, A. Abadía, J. D. L. Rivas, and J. Abadía Responses of Sugar Beet Roots to Iron Deficiency. Changes in Carbon Assimilation and Oxygen Use Plant Physiology, October 1, 2000; 124(2): 885 - 898. [Abstract] [Full Text]

				M. A. Schoenbeck, S. J. Temple, G. B. Trepp, J. M Blumenthal, D. A. Samac, J. S. Gantt, G. Hernandez, and C. P. Vance Decreased NADH glutamate synthase activity in nodules and flowers of alfalfa (Medicago sativa L.) transformed with an antisense glutamate synthase transgene J. Exp. Bot., January 1, 2000; 51(342): 29 - 39. [Abstract] [Full Text] [PDF]

				M. Watt and J. R. Evans Linking Development and Determinacy with Organic Acid Efflux from Proteoid Roots of White Lupin Grown with Low Phosphorus and Ambient or Elevated Atmospheric CO2 Concentration Plant Physiology, July 1, 1999; 120(3): 705 - 716. [Abstract] [Full Text]