This paper analyzes the effect of exogenous urea in increased concentration gradient (0, 100, 500 and 1,000 mg L−1) on photosynthetic pigments (measured spectrophotometrically), uptake of 14CO2 (using radioisotope), and urease activity (by measuring ammonia with Nessler’s reagent) in leaves of Elodea densa Planch. We have observed that low concentration of urea (100 mg L−1) stimulates the accumulation of photosynthetic pigments and intensifies photosynthesis in E. densa, whereas high concentration (1,000 mg L−1) suppresses these processes. Urease activity increased by approximately 2.7 and 8 fold when exogenous urea concentrations were 100 and 500 mg L−1, respectively. However, exogenous urea in high concentration (1,000 mg L−1) decreased urease activity by 1.5 fold compared to the control. The necessity of mitigating urea and other nitrogen-containing compounds (NH3 from urea) in water bodies has been discussed with emphasis on the potential for phytoremediation of urea using common water weed viz. E. densa.
