Arylsufatase activity in the rhizosphere and roots of different crop species

Abstract

It is assumed that arylsulfatase contributes to the mineralization of organic S to SO 4 2− for plant uptake. However, the impacts of agronomic measures (long-term organic manure) or crop species on enzyme activity are not well understood. Therefore, in the present investigations arylsulfatase activity was quantified within the rhizosphere of Sinapis album, Lolium perenne, Triticum aestivum and Brassica napus, grown on three different soils from a long-term field experiment. Highest activities were found within 0.25 mm from the root surface. Highest over all activities were found with B. napus and T. aestivum, lowest with S. album and L. perenne at a distance of 1.75 mm. As compared to soil supplemented with mineral fertilizer, compost and farmyard manure, respectively, arylsulfatase activity was higher in the soil with long-term compost application. In the protein extracts of sterile-grown roots a low arylsulfatase activity could be detected. The enzyme is induced under sulfate deficiency conditions. Preliminary biochemical data obtained from studies with T. aestivum arylsulfatase indicate conformity with biochemical properties of arylsulfatases originated from micro-organisms, vertebrates and invertebrata. From our results we assume that arylfulfatase activity determined in roots of sterile-grown plants is derived from endophytic bacteria and not by higher plants.