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

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 ph osphodiesterase (PDEase) activities of shoot tips were measured using para- nitrophenyl phosphate (p-NPP) and bis-pNPP. All species showed PMEase activ ity, but not all showed PDEase activity. The mean pH optimum was 5.0 for PM Ease and 5.7 for PDEase. The kinetic parameters K-m and V-max were calculat ed from three linear transformations of the Michaelis-Menten equation. The mean K-m values of the mosses ranged between 77 and 468 muM for PMEase and 26 and 414 muM for PDEase. The corresponding V-max values were 0.6-205 mu m ol pNP g(-1) DW h(-1) for PMEase and 1.4-110 junol pNP g(-1) DW h(-1) for P DEase. Mosses from Sweden displayed greater K-m and smaller V-max values th an those from England. The aquatics Fontinalis antipyretica and Rhynchosteg ium riparioides displayed two-phase kinetics for PMEase and PDEase, with K- m and V-max being dependent on substrate concentration. Staining suggested that PMEase activity was located in the cell wall of most mosses. Phosphata se assays provide a rapid method for screening environmental nutrient statu s and a standard procedure is recommended.