The Role of Desert Cryptogams in Nitrogen Fixation

Snyder, Jenise M.; Wullstein, L. H.

doi:10.2307/2424451

Cited by 38 publications

(14 citation statements)

References 11 publications

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“…When higher plants are absent, phototrophic microorganisms inhabiting crusts represent the sole source of primary production for the ecosystem. When they are capable of fixing atmospheric nitrogen (N 2 ), as it is often the case, they can also contribute to increase the nitrogen content of the soil [27]. Using microsensor techniques, Garcia-Pichel and Belnap [6] have shown that oxygen dynamics in desert crusts were in the same order of magnitude as those observed in microbial mats, which are known to be among the most productive aquatic ecosystems on Earth [4].…”

Section: Introductionmentioning

confidence: 99%

Hydrotaxis of Cyanobacteria in Desert Crusts

Pringault¹,

García-Pichel

2003

Microb Ecol

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We studied the migration of cyanobacteria in desert crusts from Las Bárdenas Reales (Spain). The crusts were almost exclusively colonized by the filamentous cyanobacterium Oscillatoria, which formed a dense layer approximately 600 lm thick located between 1.5 and 2.1 mm deep. Laboratory and field experiments showed that saturation of the crust with liquid water induced a migration of the cyanobacteria leading to a significant greening of the surface within a few minutes. Under light and rapid evaporation, the green color rapidly disappeared and the crust surface was completely devoid of filaments within 60 min. In contrast, 260 min was required to recover the original white color of the crust when slow evaporation was experimentally imposed. The up and down migration following wetting and drying occurred also in the dark. This demonstrates that light was not a required stimulus. Addition of ATP synthesis inhibitors prevented the cyanobacterium from migrating down into the crust, with filaments remaining on the surface. Therefore, the disappearance of the green color observed during desiccation can only be attributed to an active cyanobacterial motility response to the decrease in the water content. The simplest explanation that can account for the evidence gathered is the presence of a mechanism that links, directly or indirectly, these motility responses to gradients in water content, namely a form of hydrotaxis.

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Section: Introductionmentioning

confidence: 99%

Hydrotaxis of Cyanobacteria in Desert Crusts

Pringault¹,

García-Pichel

2003

Microb Ecol

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“…King and Ward (1977) showed that phosphorus was the major growth-nutrient in soil. The cryptogamic crust community imparts other benefits to the desert ecosystem, including the fixation of significant amount atmospheric nitrogen by blue-green algae as well as by bacteria associated with certain moss species (Snyder and Wullstein, 1973;Rychert and Skujins, 1974;Reddy and Giddens, 1975;St. Clair et al, 1984).…”

Section: Resultsmentioning

confidence: 99%

A Comparative Study of Algal Communities on Cultivated and Uncultivated Soils

Issa¹,

Adam²,

Muhammad³

et al. 2000

Pakistan J. of Biological Sciences

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Abstract:The algal communities of cultivated land, reclaimed desert and waste land in relation to physico-chemical characters were followed during the study period (1996)(1997). Organic carbon, ammonia-N and Phosphate levels of soil samples are the major controlling factors affecting algal growth and distribution of algae in these sites. Also, the diversity of algal species was strongly affected by vegetation seasons. The decrease number of algae in the waste land compared to other soil samples may be due to high salinity of this soil. A positive correlation of algal abundance and diversity (mainly diatoms and green algae) during succession with levels of PO 4 -P was observed in reclaimed desert. Blue-green algae were more dominant in the cultivated soil and waste soil than in reclaimed desert.

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“…growing on the crusts. Very low rates of acetylene reduction have been found to be associated with mosses and lichens growing in semiarid shrub/bunchgrass communities in southern Idaho and western Utah (Snyder and Wullstein 1973). Vlassak et al (1973) also reported low rates to be associated with Ceratodon purpureas and Nostoc spp.…”

Section: Discussionmentioning

confidence: 99%

Evaluation and significance of associative dinitrogen fixation for arid soil rehabilitation

Wullstein

1989

Arid Soil Research and Rehabilitation

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There are indications that in soils of arid lands associative dinitrogen fixation may be an important factor in providing plants with nitrogen. The actual values of fixation rates and amounts of nitrogen accessible to vegetation are difficult to determine due to inherent difficulties with the commonly used acetylene reduction methodology. It appears, however, that the arid zone plant species forming rhizosheaths are best suited for rehabilitation purposes. The rhizosheath-forming plant species show more consistent and higher dinitrogen fixation rates than those without the rhizosheaths. In general, the phenomenon of dinitrogen fixation by root-associated, nonnodule-forming organisms is poorly understood. There is a dire need for experimental work with 15 N 2 in the field to ascertain the actual amounts of fixed dinitrogen delivered to vegetation in various environmental situations.

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The Role of Desert Cryptogams in Nitrogen Fixation

Cited by 38 publications

References 11 publications

Hydrotaxis of Cyanobacteria in Desert Crusts

Hydrotaxis of Cyanobacteria in Desert Crusts

A Comparative Study of Algal Communities on Cultivated and Uncultivated Soils

Evaluation and significance of associative dinitrogen fixation for arid soil rehabilitation

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