IMPORTANCE OF AMMONIA DETOXIFICATION BY PLANTS IN PHYTOREMEDIATION AND AQUAPONICS

Pure ammonia is a gas which is highly soluble in water. As a base, under neutral conditions it exists as ammonium ion, which, at low external concentrations is a preferential nitrogen source for most plants but at higher concentrations it is phytotoxic. Since ammonia is continuously produced in living plant cells by different biochemical processes, several routes evolved for its detoxification. However, even the most active detoxification pathways cannot protect the plants against high concentrations of ammonia applied exogenously under the conditions of phytoremediation and aquaponics. Phytoremediation and aquaponics are new, emerging, ecofriendly technologies that exploit the high stress tolerance of plants by growing them under atypical, occasionally highly stressful conditions. Phytoremediation uses living higher plants for cleaning up contaminated soil and water by removing, sequestering, or biochemically decomposing the pollutant. Aquaponics integrates hydroponics (plant production in water, without soil) and traditional aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks), providing a symbiotic environment for producing fish and plants in a closed system. In phytoremediation plants may be exposed to a wide range of pollutants while in aquaponics the usual phytotoxic pollutant is ammonia produced by the fish.