Effect of organic and inorganic carbon on extracellular enzyme activity of acid phosphatase and proteases in three kinds of fungal hyphae.

Abstract

Most researches have manifested that mycorrhizal fungi can promote plant nutrient absorption and improve plant growth,but the effects of the hyphae on soil nutrient exploitation were less reported.Through laboratory control test of 3 kinds of fungi,Lactarius deliciosus,Russula integra and Gomphidius viscidus in this paper,N,P related extracellular enzymes exuding from variable fungal hyphaes(acid phosphatase and proteases) was found.In most cases,each enzymatic activity of these 2 enzymes was the highest in 2 weeks culture in MMN medium,while short(one week) or long(3 weeks) may reduce their activities.However, different fungus significantly differed in the enzyme activity,and G.viscidus had the lowest activity of acid phosphatase,while the highest in protease activity.No significant difference was found in the other two fungus; Secondly,addition of organic carbon(humic acid,HA) and inorganic carbon(calcium carbonate) could significantly affect the activities of acid phosphatase and protease.When HA was added,the activity of acid phosphatase steadily increased in 3 fungus,while fungus-specific patterns were found in protease activity,i.e., continuous increasing activity of protease in L.deliciosus protease was observed,while less HA-sensitivity was found in R.integr and G.viscidus;Thirdly,small amount of calcium carbonate addition could enhance the exudation of these two enzymes of acid phosphatase and protease,while adding more may reduce the enzymatic activities(e.g.0.1 g).To sum up,fungal hyphaes can secrete acidic phosphatase and acid protease,and these enzymes may promote the activation of ineffective organic P and N and enhance plant growth.Soil organic carbon accumulation and depletion of inorganic carbon could directly increase the extracellular enzyme secretions of all tested fungal hyphae,showing the function of hyphae in soil carbon cycle.