title: Effect of tryptophan on 2,4-dichlorophenoxyacetic acid toxicity in the nitrogen-fixing-cyanobacterium Nostoc linckia.
abstract: The combined effect of a hormone weed killer 2,4-dichlorophenoxyacetic acid (2,4-D) and an amino acid (tryptophan) has been studied on growth and heterocyst differentiation in the cyanobacterium Nostoc linckia. 2.4-D at 100 micrograms/ml stimulated growth and heterocyst frequency in combined nitrogen-free medium while its higher concentrations inhibited both. Tryptophan under similar conditions promoted much growth yield with 3-4 fold enhanced heterocyst frequency than the control. Such heterocysts were immature and showed germination under in situ condition. The concentrations of 2,4-D (100 micrograms/ml) and tryptophan (50 micrograms/ml), stimulatory to growth and heterocyst formation, caused additive effect while herbicide inhibition of nitrogen-fixing growth at higher doses was partially relieved by tryptophan but tryptophan-induced heterocyst frequency was completely suppressed under this condition. The possible role of interaction of these two chemicals on growth and heterocyst formation has been discussed.
authors.forename: A K
authors.initials: AK
authors.lastname: Mishra
authors.forename: D N
authors.initials: DN
authors.lastname: Tiwari
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism / Q000494:pharmacology*; D000458:Cyanobacteria / Q000187:drug effects* / Q000254:growth & development; D004237:Diuron / Q000494:pharmacology; D004347:Drug Interactions; D005947:Glucose / Q000494:pharmacology; D009586:Nitrogen Fixation / Q000187:drug effects; D014364:Tryptophan / Q000494:pharmacology*
chemical_list: D015084:2,4-Dichlorophenoxyacetic Acid; D014364:Tryptophan; D004237:Diuron; D005947:Glucose