Nitrogen fixation associated with seagrasses1

McRoy, C. Peter; Goering, John J.; Chaney, Barbara

doi:10.4319/lo.1973.18.6.0998

Cited by 65 publications

(37 citation statements)

References 4 publications

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“…However, in Z. marina, no activity was observed over the first 24 h ofassay. Subsequent examinations of Z. marina roots and rhizomes by McRoy et al (10) failed to detect any associated nitrogenase activity. They (10) suggested that the extended periods oftime needed for sample transportation and assay by Patriquin and Knowles (15) may have resulted in bacterial proliferation.…”

Section: Discussionmentioning

confidence: 99%

Nitrogen Fixation Associated with Rinsed Roots and Rhizomes of the Eelgrass Zostera marina

Capone

Budin²

1982

Plant Physiol.

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Nitrogen fixation was associated with the rinsed roots and rhizomes of the seagrass, Zostera marina L. Nitrogenase activity (acetylene reduction) was greater on rhizomes compared to roots, and on older roots and rhizomes relative to younger tissue. Compared to aerobic assays, anaerobic or microaerobic conditions enhanced the rate of acetylene reduction by rhizomes with attached roots, with the highest activity (100 nanomoles per gram dry weight per hour) occurring at PO2 = 0.01 atmosphere. Addition of glucose, sucrose, or succinate also increased the rate of acetylene reduction under anaerobic conditions, with glucose providing the most stimulation. In one experiment, comparison of acetylene reduction assays with '5N2 incorporation yielded a ratio of about 2.6:1. Seagrass communities are thought to be limited by the availability of nitrogen and, therefore, nitrogenase activity directly associated with their roots and rhizomes suggests the possibility of a Nrfixing flora which may subsidize their nutritional demand for nitrogen.In seagrass communities, as in many marine ecosystems, nitrogen in a combined form is often present at limiting levels (12, 13). Nonetheless, these communities are very prolific (11). Nitrogen fixation has been detected in rhizosphere sediments of several seagrasses (4, 6). The presence of a root-associated N2-fixing flora would assist in reconciling the observed productivities of these marine angiosperms with apparent nutrient impoverishment.The objectives of this study were 3-fold: (a) to locate within the rhizosphere the predominant sites ofnitrogen fixation; (b) with bay water to the laboratory. The time span between sampling and laboratory work was about 1 to 2 h. Upon return to the laboratory, emergent leafmaterial was removed from the sediment surface. The remaining roots, rhizomes, and sediment were placed into flasks containing nucleopore (0.2 pm) filtered Bellport bay water. These procedures were carried out while gassing with O2 free N2. The bubbling action effectively rinsed the roots and rhizomes of sediment and minimized exposure to O2 during assay set up. Approximately five 2-to 3-cm segments of roots and/or rhizomes were transferred into each of at least twelve 125-ml Erlenmeyer flasks containing 25 ml of filtered bay water. The flasks were sealed with rubber stoppers following an additional 2 min ofbubbling with N2 and then were evacuated and backflushed with N2 four to five times to ensure anaerobic conditions. Acetylene Reducdon Assays. The acetylene reduction technique (7), as adapted for use in seagrass systems (4, 6), was employed to measure nitrogenase activity. The flasks were placed into a 25°C shaking (100 rpm, rotary) water bath followed by the addition of 12.5 ml acetylene (pC2H2 = 0.12 atm). Preliminary experiments indicated saturation by 0.10 atm pC2H2. Ethylene and acetylene concentration were measured by flame ionization gas chromatography (4, 6).In all assays, triplicate flasks were incubated at each level of an experiment. In one experiment, rhiz...

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Section: Discussionmentioning

confidence: 99%

Nitrogen Fixation Associated with Rinsed Roots and Rhizomes of the Eelgrass Zostera marina

Capone

Budin²

1982

Plant Physiol.

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“…The excised root assay for the determination of nitrogen fixation in grasses also received criticism because of the long incubation times with or without acetylene (3,17,19,27,28). This procedure was specifically questioned in conjunction with proliferation of the associated nitrogen-fixing microflora during the prolonged incubation periods (19,28).…”

Section: Discussionmentioning

confidence: 99%

Immediate Acetylene Reduction by Excised Grass Roots Not Previously Preincubated at Low Oxygen Tensions

Berkum

Sloger²

1979

Plant Physiol.

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“…In comparison, Patriquin & Knowles (1972) estimated N fixation rates of 100-500 kg N ha" 1 y" 1 in beds of Thalassia testudinum in the Carribean and 5-10 kg N ha" 1 y" 1 in non-rhizosphere sediments. However, on examination of N fixation associated with Thalassia from Florida, McRoy et al (1973) found only low maximum rates of 29 \ig N m~2 day" 1 , or 0.106 kg N ha" 1 y" 1 . Bohlool & Weibe (1978) demonstrated rates of N fixation ranging between 1 and 200 g N ha" 1 day 1 from different intertidal sources in New Zealand not associated with marine angiosperms.…”

Section: Resultsmentioning

confidence: 99%

“…Though we did not attempt to identify acetylene reduction associated with surface and rhizosphere sediments separately from that associated with the phyllosphere, the correlation with root weight suggests that rhizospherebased activity is dominant. However, McRoy et al (1973) found acetylene reduction to be associated predominantly with leaves of Thalassia testudinum, a seagrass collected from Florida, USA. This activity was also light-dependent, suggesting cyanobacterial origin.…”

Section: Resultsmentioning

confidence: 99%

“…In Zostera species, nitrogenase activity has been found in material from New Brunswick, Canada; Alaska, USA; and South Africa (Patriquin & Knowles 1972;McRoy et al 1973;Talbot et al 1988). In Spartina species, nitrogenase activity has been found in material from Nova Scotia, Canada; South Carolina, USA; and South Africa (Patriquin & McClung 1978;Gandy & Yoch 1988;Talbot et al 1988).…”

Section: Discussionmentioning

confidence: 99%

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Acetylene reduction associated withZostera novazelandicaSetch. andSpartina alternifloraLoisel., in Whangateau Harbour, North Island, New Zealand

Hicks

Silvester

1990

New Zealand Journal of Marine and Freshwater Research

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Nitrogen fixation (acetylene reduction) was investigated in Zostera novazelandica Setch. and Spartina alterniflora Loisel., in the North Island of New Zealand. Moderate rates of acetylene reduction were found in sediments in which plants were growing (means ± 95% confidence limit: 15.2 ± 2.8 μmol C 2 H 4 m -2 h -1 for Zostera and 24.7 ± 4.6 |amol C 2 H 4 m -2 h -1 for Spartina). Activity was closely correlated with the dry weight of roots (r 2 = 0.65, N -15 for Zostera, and r 2 = 0.85, N = 10 for Spartina). Sediment close to the plant beds, but without plants, exhibited only low rates of acetylene reduction (2.9 ± 2.2 and 4.5 ± 1.0 pmolC 2 H 4 m 2 h -1 ,respectively). Sediments associated with Z. novazelandica and S. alterniflora in New Zealand exhibit moderate rates of nitrogenase activity compared to rates found in other countries. N fixation may contribute significantly to the nutrition of these plants in New Zealand estuaries.

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Nitrogen fixation associated with seagrasses1

Cited by 65 publications

References 4 publications

Nitrogen Fixation Associated with Rinsed Roots and Rhizomes of the Eelgrass Zostera marina

Nitrogen Fixation Associated with Rinsed Roots and Rhizomes of the Eelgrass Zostera marina

Immediate Acetylene Reduction by Excised Grass Roots Not Previously Preincubated at Low Oxygen Tensions

Acetylene reduction associated withZostera novazelandicaSetch. andSpartina alternifloraLoisel., in Whangateau Harbour, North Island, New Zealand

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