ISSN:
1573-5036
Keywords:
Anthoceros
;
Azolla
;
Blasia
;
Gunnera
;
Macrozamia
;
N2 fixation
;
Peltigera
;
Symbiotic cyanobacteria
;
SymbioticNostoc andAnabaena
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary N2-fixing cyanobacteria occur in symbiotic associations with fungi (ascomycetes) as lichens and with a few green plants. The associated cyanobacterium is always a species ofNostoc orAnabaena. Only a small number of plant genera are involved but there is a remarkable range of host diversity. Associations occur with several bryophytes (e.g.Anthoceros, Blasia, Cavicularia), a pteridophyte (Azolla), cycads (nine genera includingMacrozamia andEncephalartos) and an angiosperm (Gunnera). Except forGunnera, where the cyanobacterium penetrates the plant cells, the cyanobacteria are extracellular with specialized morphological modifications and/or structures of the host plant organs providing an environment which facilitates interaction with the prokaryote. Salient aspects of current knowledge pertaining to the establishment, perpetuation, and functioning of the individual symbioses are summarized. Where possible this includes information concerning recognition and specificity, mode(s) of infection, morphological modifications/adaptations of the host plant and a synopsis of morphological, physiological and biochemical changes common to the symbiotic cyanobacteria. The latter encompasses heterocyst frequencies, enzymes involved in ammonia assimilation, photosynthetic capability and metabolic interaction with the host. TheAzolla-Anabaena symbioses, which have potential agronomic significance as an alternative nitrogen source and maintain continuity with the endophyte through the sexual cycle, are emphasized.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02277384
Permalink
