有机碳和无机碳对3种真菌胞外酸性磷酸酶和蛋白酶活性的影响

Effect of Organic and Inorganic Carbon on Extracellular Enzyme Activity of Acid Phosphatase and Proteases in Three Kinds of Fungal Hyphae

多数研究表明外生菌根真菌能够促进植物养分吸收并提高植物生长,但是对其发生的原因研究较少。本文在室内控制条件下,研究了真菌菌丝分泌N、P相关胞外酶及其受土壤有机碳(胡敏酸)和无机碳(碳酸钙)添加的影响,结果表明:1)3种真菌——松乳菇(Lactarius deliciosus)、变色红菇(Russula integra)、铆钉菇(Gomphidius viscidus)菌丝均能够分泌酸性磷酸酶和蛋白酶,而且多数情况下,MMN培养基培养14 d时,各个酶活性较高,而不同菌的胞外酶活性存在较大的差异,平均值来看铆钉菇酸性磷酸酶活性最低而蛋白酶活性最高,其它2个真菌菌丝的胞外酶活性差异不大;2)添加胡敏酸后,3种菌丝的酸性磷酸酶活性都是随着胡敏酸添加量的增加而逐渐增加;但蛋白酶活性存在差异:松乳菇的蛋白酶活性随着胡敏酸添加量的增加而逐渐增加;变色红菇的蛋白酶活性对胡敏酸不敏感,受其影响不大;铆钉菇的蛋白酶活力在少量的胡敏酸作用下最强,但浓度过高反而抑制其蛋白酶的活性。3)添加碳酸钙后,总体来看,3种菌丝胞外酸性磷酸酶和蛋白酶活性都是添加少量碳酸钙时酶活性最强,随着浓度的增加(如0.1 g),其酶活性开始受到抑制。综上所述,真菌菌丝能够分泌酸性磷酸酶和蛋白酶,这可能是因为这些外生菌根真菌能够促进植物养分吸收和快速生长的原因;有机碳和无机碳的加入可以直接影响真菌菌丝胞外酶的分泌,进而影响土壤内有机磷和有机氮化合物的分解,显示其在土壤碳循环中的作用。

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 v/sc/dus 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. O. 1 g）. To sum up, fungal hyphaes can secrete acidic phosphatase and acid protease, and theseenzymes 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 htphae in soil carbon cycle.