Annual variations of phenoloxidase activities in an evergreen oak litter: influence of certain biotic and abiotic factors

• Published in: Soil biology & biochemistry Vol. 32; no. 11; pp. 1505 - 1513
• Main Authors: Criquet, S, Farnet, A.M, Tagger, S, Le Petit, J
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2000; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; France; Fundamental and applied biological sciences. Psychology; Fungi; Humic substances; Laccase; Litter; Organic matter; Peroxidase; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Quercus ilex; Soil science; France; Provence Alpes Côte d'Azur; Europe; Var; Fungi; Peroxidase; Litter; Humic substances; Laccase; Annual variation; Enzyme; Mediterranean vegetation; Soil moisture; Environmental factor; Catechol oxidase; Biogeochemical cycle; Quercus ilex; Fagaceae; Microbial biomass; Ligninolytic enzyme; Enzymatic activity; Peroxidases; Dicotyledones; Angiospermae; pH; Hardwood forest tree; Spermatophyta; Oxidoreductases; Mediterranean climate; Soil temperature; Diarylpropane peroxidase
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/S0038-0717(00)00027-4

This study concerns ligninolysis phenomena occurring over 13 months in forest litter. Evergreen oak ( Quercus ilex L.) litter was taken as a model because Quercus ilex L. is the most abundant tree species in forests of the French Mediterranean area. Several biotic and abiotic factors potentially involved in transformations of polyphenolic compounds, were measured between October 1997 and October 1998. These factors were: global fungal microflora, the fungi producing phenoloxidases (PO +), the activities of several phenoloxidases, hydrosoluble phenols, and temperature, humidity and pH of the litter. Results showed that the annual dynamics of fungi and phenoloxidase activities appear to be seasonal, i.e. that these biotic factors such as, were optimal in autumn. A multiple regression analysis showed that there was no correlation between biotic factors such as, fungal populations and phenoloxidase activity and abiotic factors such as, temperature, humidity and pH. Laccases were the preponderant phenoloxidase activities during the year, while those of Mn-peroxidases only appeared in the autumn of 1997. Other phenoloxidases, lignin-peroxidases and tyrosinases were never detected. Interactions between laccases and humic substances were also investigated. Adsorption of laccases on humic substances leads to a shift in the optimal temperature activity of these enzymes from 50 to 30°C. Activities of laccases also shifted towards more acidic values when laccases were not adsorbed on humic substances. Nevertheless, the optimal pH was the same (5.7) whether laccases were adsorbed or not to humic substances. Electrophoresis analysis showed little variations in the number of phenoloxidase isoenzymes. Indeed, laccases showed three isoenzymes during the year ( R f 0.23, 0.34 and 0.43). Only one isoform of Mn-peroxidase, with an Rf 0.21, was detected in the litter.