Resistance of dehydrogenases, catalase, urease and plants to soil contamination with zinc

Abstract

Pot trials on growing plants were conducted in order to determine the resistance of de- hydrogenases, catalase and urease as well as the plants themselves to soil contamination with zinc. The experimental variables were: the type of soil (loamy sand and sandy loam), degree of soil pollution with zinc from 0 to 600 mg Zn 2+ kg -1 d.m., and plant species (oat, spring rape and yellow lupine). Samples of soil were tested to determine the activity of dehydrogenases, catalase and urease as well as its physicochemical properties. Based on the enzymatic activity of soil and the dry matter of harvested plants, the resistance of enzymes and each of the crops was deter- mined to excessive amounts of zinc in soil with different grain-size distribution. It was conc- luded that zinc contamination significantly inhibited the activity of dehydrogenases, catalase and urease. With respect to their sensitivity to zinc, the enzymes were arranged in the following order: dehydrogenases > urease > catalase. The plant species and grain-size distribution of soil determined the resistance of the enzymes to zinc pollution. Dehydrogenases were most resistant to zinc in soil cropped with oat, urease - in soil under spring rape and catalase - in soil sown with yellow lupine. Dehydrogenases and urease were more resistant to the adverse influence of zinc in sandy loam than in loamy sand, contrary to catalase, which was less vulnerable in loamy sand than in sandy loam. Tolerance of plants to zinc pollution proved to be a species-specific characteristic. Yellow lupine was most sensitive to excess zinc in soil, while oat was most re- sistant to the said contamination out of the three examined plant species.