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Articles

Nitrogenase Activity Associated with Roots and Stems of Field-Grown Corn (Zea mays L.) Plants ¹

Department of Soils and Crops, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, New Jersey 08903, Department of Horticulture and Forestry, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, New Jersey 08903, Department of Biochemistry and Microbiology, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, New Jersey 08903

Corn (Zea mays L.) plants were assayed for nitrogenase activity (C₂H₂ reduction) during early ear development. Hybrid corn and inbred lines were grown separately at two experimental fields in New Jersey. Acetylene-dependent ethylene production was observed a few hours after harvest, from the field, on intact plants, root-soil cores, lower stem segments, and excised roots, all assayed under air and not preincubated previously. Incubation of excised roots at 1% O₂ resulted in lower rates of C₂H₂ reduction. The time course of C₂H₂ reduction by excised roots, assayed in air, was similar for all genotypes studied (two hybrids, eight inbreds, and a cross of corn x teosinte) and indicated that a long preincubation at reduced O₂ is not absolutely required for early detection of nitrogenase activity. Isolation of N₂-fixing bacteria from within the roots and stems, together with the diurnal fluctuation of nitrogenase activity in response to day/night cycles, were indicative of a close association with plant function. Collectively, the results provided strong evidence for the occurrence of nitrogenase activity associated with corn plants growing in a temperate climate and dependent upon indigenous N₂-fixing bacteria.

³ Present address: Department of Horticulture, Penn State University, 103 Tyson Bldg. University Park, PA 16802.

⁴ Corresponding author.

¹ Supported partially by a Rutgers Research Council grant to C. A. N. New Jersey Agricultural Experiment Station Publication No. D-01203-1-82, supported by State funds and by United States Hatch Act funds to C. A. N.