Physiological studies on the role of cyanobacteria in ameliorating the toxic effects of copper in Trigonella foenum gracum. The goal of the study was to assess the influence of Nostoc muscorum on the inhibitory effects of copper stress imposed on Trigonella foenum gracum as manifested in its growth and some metabolic activity as a trial to alleviate the copper toxicity. Application of Nostoc in a mixture with Cu significantly increased all growth parameters, photosynthetic pigments and activity, soluble and insoluble nitrogen.Moreover, the activity of both peroxidase (POD) and superoxide dismutase (SOD) were reduced by applying Nostoc to the soil having different concentrations of Cu. Mixing Nostoc with Cu increased the percentage of unsaturated fatty acids when compared with control and Cu singly. Isozyme profile of POD and and beta-esterase of yielded seeds showed 3 isoforms of POD and esterase and two isoforms of beta-esterase varied in their intensity and thickening in response to different treatments.