الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
)- The concept ” environment select ” for diazotrophic cyanobacteria was monitored in a series of short-term laboratory and a field experiments . The laboratory experiments were first started by the isolation and identification of different cyanobacterial isolates ( Nostoc maculiforme , Nostoc humifusum and Wolla sp.) from rice soils . Besides the isolated cyanobacterial strains i.e. nostoc caicicola , Anabaena flos aquae , Nostoc muscorm , Anabaena laxa and microchate tenra , five local cyanobacterial strains were all being initially evaluated for growth and atmospheric N2-fixation through determination of the nitrogenase activity (N-ase) after which the most six efficient nitrogen fixing cyanobacterial strains were examined when being exposed to various environmental stimulators or constraints