The aim of the study was to investigate the influence of bermudagrass on growth components, physiology parameters (stomatal aperture, leaf transpiration, carbon dioxide intake, leaf temperature, Fv/Fm values and net assimilation rate) and concentration of important nutrients (N, P, K, Mg, Ca) in leaves and roots of cotton. Cotton seedlings and bermudagrass plantlets were growing adjacently in a Hoaglands nutrient solution of ½ strength, which was continuously circulated. Under the influence of bermudagrass, cotton suffered significant reduction of stomatal aperture, leaf transpiration, CO2 intake, Fv/Fm values, net assimilation rate and significant increase in leaf temperature. No differences were recorded between control and treatment in nutrient concentration in leaves. On the contrary, in cotton roots due to the influence of bermudagrass, Mg was increased by 29.2, P by 63.2 and Ca by 297.4%. Consequently the growth of plants in treatment was significantly inferior than control. Reduction was recorded at 54.6% for stem dry matter, at 35.5% for stem diameter, at 55.3% for leaves dry matter and 46.2% for root dry matter. Growth inhibition and deterioration of photosynthesis components (specifically Fv/Fm values) indicate that cotton suffered serious allelopathic stress due to the weed influence. Stress effect was pronounced although plants were growing in the nutrient solution, were no adverse factor to limit growth was observed. The allelopathic effect was exhibited by the weed, although it was not stressed in the nutrient solution. Dilution of allelochemicals in a high volume solution didn't reduce activity of allelochemicals.