Biological Nitrogen Fixation for Food and Fiber Production

Evans, Harold J.; Barber, Lynn E

doi:10.1126/science.197.4301.332

Cited by 139 publications

(34 citation statements)

References 59 publications

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“…These diazotrophic symbionts all cluster within the polyphyletic group of rhizobia, which includes α and β-proteobacteria. Thanks to these associations, rhizobia are considered as the most efficient heterotrophic N 2 -fixers as they receive carbon fixed by their photosynthetic host (Evans and Barber, 1977;Van Rhijn and Vanderleyden, 1995). In the marine environment it is well known that diazotrophic bacteria have developed symbiotic relationships with seagrass (Capone, 1983).…”

Section: Non-cyanobacterial Diazotrophs Richness Recoverymentioning

confidence: 99%

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

2011

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Abstract. The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study, we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH genes phylogenies. These genetic analyses were possible owing to the development of a new PCR protocol adapted to scarce microorganisms that can detect as few as 1 cell ml −1 in cultures. Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized to the Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml −1 of Richelia were detected in the eastern basin, while small (0.7-1.5 µm) and large (2.5-3.2 µm) Nitro821-targeted cells were recovered at all stations with a mean concentration of 3.5 cell ml −1 . The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. In the central and the eastern Mediterranean Sea no 16S rDNA and nifH sequence from UCYN was obtained as cells concentration were close to, or below PCR detection limit. Bradyrhizobium sequences dominated nifH clone libraries from picoplanktonic size fractions. A few sequences of γ -proteobacteria were also detected in the central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the developCorrespondence to: I. C. Biegala (biegala@univmed.fr) ment of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles, and/or photosynthetic activity, to acquire carbon for sustaining diazotrophy.

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Section: Non-cyanobacterial Diazotrophs Richness Recoverymentioning

confidence: 99%

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

2011

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“…Assuming an aririnal growth rate of emissions of 5 percent , since these , presumably , track the worldwide use of fossil fuel . gives an estimated combustion source of 10.9 Evans and Barber (1977), leads to a change in biological nitrogen fixation resulting from this change of U.S. soybean production of 0.6 ~4 t ( N ) to 1.7 -: t ( N ) --numbers which are not in s i g n i f i c a n t , but s t i l l are less t h a n 14 percent of industrial or combustion fixation taken separately.…”

Section: F 2 2 the Combustion Source Of Fixed Nitrogenmentioning

confidence: 99%

“…MItro~en fixation rates in k~Yhectare-year are 57 to 914 for soybeans , and 128 to 600 for alfalfa , with other legumes generally lying between these limits (see Evans and Barber , 1977).…”

Section: F 2 2 the Combustion Source Of Fixed Nitrogenmentioning

confidence: 99%

A catalog of perturbing influences on stratospheric ozone, 1955–1975

Bauer¹

1979

J. Geophys. Res.

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There exist worldwide data on the total burden of atmospheric ozone since about 1955, and for comparison of these data with calculations using two‐dimensional radiative/chemical/dynamics computer codes, a list is needed and is here presented of all major time‐varying perturbations that have been suggested over the time frame 1955–1975. Detailed consideration is given to the following: variations in solar UV radiation with sunspot cycle, atmospheric nuclear explosions, halocarbons, major volcanic eruptions, galactic cosmic rays, and solar proton events. For material injected directly into the stratosphere, the time‐, altitude‐, and latitude‐dependent source strengths are listed, while for ground‐based sources the time‐ and latitude‐dependent atmospheric emission rates are given. Some other factors that may affect the long‐term behavior of stratospheric ozone but that cannot yet be modeled quantitatively are also listed.

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“…are adjusted to each other's requirements. There are numerous such beneficial symbiotic or associative systems related to N-fixation alone (for references see Evans and Barber, 1977;Marx, 1977).…”

Section: Probable Parameters Of Genetic Engineering In Plant Improvementmentioning

confidence: 99%

“…In symbiotic nitrogen-fixation the leguminous host plant may provide specialized membranes, cells, and enzyme systems: (i) for facilitating root infection; (ii) for active transport of substrates and products across membranes within the nodule; (iii) for hydrolysis of sucrose in the nodule; (iv) for specialized diffusion of O2 from the outside of the nodule to the bacteroids; (v) for assimilating the ammonia produced by nitrogen reduction; and (vi) for the specialized delivery of the products of N-fixation into the xylem elements where they are transported to various parts of the plant (Bergersen, 1974;Robertson er fl/., 1975;Scott, Farndon and Robertson, 1976;Evans and Barber, 1977). It appears, however, that there may be some variation possible in the interaction of host plant and micro-organism to produce a nitrogen-fixing association.…”

Section: Nitrogen Fixation In Non-leguminous Plantsmentioning

confidence: 99%

Novel Techniques of Gene Transfer and Plant Improvement: An Appraisal of Transformation in Eukaryotes

Pandey

1978

New Phytologist

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SUMMARYCertain recent theoretical and technological advances make possible the development of new techniques for combining genes from diverse sources without normal sexual hybridization. These include: (1) DNA-and phage-induced transformation; (2) protoplast fusion and organelle transfer; (3) gametic transformation; and (4) graft hybridization. The essential feature of these novel techniques is 'transformation', broadly defined here as a phenomenon in which a part of the genetic information of one organism is combined with the entire genome of another. The present article reviews these topics briefly with reference to their potential value in plant improvement, and their contribution to a better understanding of induced transformation in flowering plants.A critical consideration of differences between prokaryotic and eukaryotic DNA leads to a better appreciation of possible natural constraints operating against gene transfer across this major evolutionary hne. Since transformation is essentially a natural mechanism in prokaryotes, and occurs in place of true sexuality and recombination, the occurrence of artificial transformation in eukaryotes may be considered to indicate an inherent capacity for recombination by transformation which has been superceded by the evolutionary development ofthe sexual mechanisms, meiosis and syngamy, but which may still be expressed if appropriate conditions can be generated. Fniture major developments may lie in discovering factors and techniques which would make eukaryotic organisms 'competent' as donors and recipients in transformation. It is suggested that the egg, zygote, and early embryonic cells may be better targets for transformation than differentiated somatic cells. The rapid successive divisions following fertilization of a eukaryotic egg cell presumably place heavy (.iemands on DNA metabolism, and this may allow exogenous fragments to compete more tuvourably for integration into new DNA strands.

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Biological Nitrogen Fixation for Food and Fiber Production

Cited by 139 publications

References 59 publications

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

A catalog of perturbing influences on stratospheric ozone, 1955–1975

Novel Techniques of Gene Transfer and Plant Improvement: An Appraisal of Transformation in Eukaryotes

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