ISSN:
1432-072X
Keywords:
Cyanobacteria
;
Chroococcidiopsis
;
Chroococcus
;
Water stress
;
Photosynthesis
;
Endolithic
;
Matric
;
Osmotic
;
Taxonomy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Four strains of Chroococcidiopsis and one Chroococcus, all isolated from extreme arid desert rocks, and one marine Chroococcus, were subjected to water stress using both matric and osmotic control methods. For all Chroococcidiopsis strains, photosynthetic rates decreased with decreasing water potential. After 24h preincubation the decrease was linear but after 72h there was a sharp drop below-3400 kPa (a w≏0.976). In contrast, the two Chroococcus strains showed optimum photosynthesis between-3000 and-4000 KPa. It appears, therefore, that Chroococcidiopsis in deserts may have a different survival strategy in response to aridity than Chroococcus (rare in deserts). Absolute rates of 14CO2 uptake were higher in matric than in osmotic control systems. It is suggested that, in a matric experimental system, the water status is more representative of the natural conditions in arid environments. The consistent differences between different strains in their response to water stress suggest that this character in Cyanobacteria may be of taxonomic significance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00425938
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