Possible relationships between the acid phosphatase activities of the roots of three emergent macrophyte species and the physical and chemical features of their ambient surroundings were assessed. Sediments collected from monospecific stands of Phragmiles auslralis, Equiselum fluviatile and Typha ladfolia growing at Baltethin Reservoir, Northumberland, were analysed and as a result microsites having signifiamtly different organic and inorganic properties were selected. After standardisation of the phosphatase assay procedure it was suggested that the enzyme activity rates of P. auslralis and T. latifolia in the field corresponded to levels of P in the environment. It is also suggested that in the case of P. auslralis the amount of available N in the sediments is important. Although significant differences in total P levels were found in the E. fluviatile stand the phosphatase activities of the roots collected were non significantly different. The accuracy of the assay requires that the entire hydrolysis product formed is being released into solution for measurement, and that production of product is entirely due to the activity of extracellular enzymes. When assayed under different pH conditions all three species seemed to release product after termination of the assay or new product was formed from the action of intracellular activity. Any relationship between the amount of product retained or amounts of intracellular phosphatase activity and the pH of the medium was investigated. It is concluded that more work is needed to attempt to separate the effects of low N and low P concentrations on phosphatase activity rates of higher plants root and that perhaps P. auslralis could be of use as an indicator to the nutrient status of its environment
