Acid phosphatase activity in Pinus pinea – Tuber albidum ectomycorrhizal association

Abstract

Acid phosphatase activity of pine (Pinus pinea L.) roots was investigated in the presence or absence of the ectomycorrhizal fungus Tuber albidum Pico. Acid phosphatase activity was higher in mycorrhizal roots than in roots of uncolonized control plants. The optimum pH values for acid phosphatase were 3.5 and 5.0 for mycorrhizal roots and 5.0 for control roots. The acid phosphatase activity was inhibited by tartrate, fluoride, and molybdate ions, but a lower inhibition was exerted by orthophosphate. Mycorrhizal roots of pine possessed active acid phosphatases that hydrolyzed a wide variety of natural and synthetic phosphate esters. In particular, the enzyme was active against phytate and inorganic pyrophosphate. Two different Km values were estimated: about 0.22 mM and 2.78 mM at low and high substrate concentrations, respectively. The ultrastructural localization of acid phosphatase in mycorrhizal roots showed that the activity in the Hartig net was mainly localized in the plasmalemma of hyphae. Some lead phosphate precipitates were also observed in the middle lamella of the host cell. Key words: Pinus pinea, Tuber albidum, acid phosphatase, ectomycorrhiza, histochemical localization.