title: UV-B induced differential effect on growth and nitrogen metabolism in two cyanobacteria under copper toxicity.
abstract: In the present study, impact of low (UV-B(L): 0.1 μmol m(-2) s(-1)) and high (UV-BH: 1.0 μmol m(-2) s(-1)) fluence rates of ultraviolet-B on growth and nitrogen metabolism in two cyanobacteria: Phormidium foveolarum and Nostoc muscorum under copper toxicity (2 and 5 μM) was investigated after 24 and 72 h of experiments. Copper and UV-BH treatment suppressed growth but more in N. muscorum which was accompanied by significant accumulation of Cu. Nitrate and nitrite uptake rates and activities of nitrogen assimilating enzymes i.e. nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase (GOGAT) except glutamate dehydrogenase activity (GDH; aminating) were decreased following treatments of Cu and UV-BH, and under combined treatments the effect was greater. On contrary, UV-BL declined Cu toxicity significantly. The study concludes that Cu and UV-BH suppressed the activity of NR, NiR, GS and GOGAT (except GDH) hence decreased growth. However, UV-BL showed cross tolerance in test organisms against Cu toxicity up to certain extent. Phormidium foveolarum is comparatively less sensitive against UV-BH and excess Cu, a situation likely exists in nature, hence it may be used as a biofertilizer for sustainable agriculture.
authors.affiliation: Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Allahabad-211002, India.
authors.forename: V P
authors.initials: VP
authors.lastname: Singh
authors.forename: P K
authors.initials: PK
authors.lastname: Srivastava
authors.forename: S M
authors.initials: SM
authors.lastname: Prasad
mesh_terms: D003300:Copper / Q000633:toxicity*; D000458:Cyanobacteria / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005970:Glutamate Synthase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D050895:Nitrate Reductase (NADH) / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D050502:Nostoc muscorum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D003300:Copper; D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase; D009572:Nitrite Reductases; D050895:Nitrate Reductase (NADH); D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen