Characterization of the phosphatase activities of mosses in relation to their environment

Abstract

Phosphatase activities and environmental features were characterized for 12 terrestrial and aquatic mosses in upland northern England, along with four species sampled from subarctic Sweden. Phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities of shoot tips were measured using para-nitrophenyl phosphate (p-NPP) and bis-pNPP. All species showed PMEase activity, but not all showed PDEase activity. The mean pH optimum was 5.0 for PMEase and 5.7 for PDEase. The kinetic parameters Km and Vmax were calculated from three linear transformations of the Michaelis-Menten equation. The mean Km values of the mosses ranged between 77 and 468 μM for PMEase and 26 and 414 μM for PDEase. The corresponding Vmax values were 0.6-205 μmol pNP g-1 DW h-1 for PMEase and 1.4-110 μmol pNP g-1 DW h-1 for PDEase. Mosses from Sweden displayed greater Km and smaller Vmax values than those from England. The aquatics Fontinalis antipyretica and Rhynchostegium riparioides displayed two-phase kinetics for PMEase and PDEase, with Km and Vmax being dependent on substrate concentration. Staining suggested that PMEase activity was located in the cell wall of most mosses. Phosphatase assays provide a rapid method for screening environmental nutrient status and a standard procedure is recommended.