Effects of needle cutting and larval herbivory on systemic induction of antioxidant defense enzymes in Larix gmelinii

Abstract

Antioxidant defense enzymes are important components in induced defense responses of plants. Activities of the antioxidant defense enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in Larix gmelinii Rupr. seedlings stressed by needle cutting or feeding by Dendrolimus superans Butler larvae (Lepidoptera: Lasiocampidae) were compared. Both cutting needles and larval feeding increased antioxidant defense enzyme activities. The maximum activities of antioxidant defense enzymes induced by the two treatments appeared after similar time lags following cutting or feeding, but the intensity and duration of enzyme activities in needles differed. D. superans feeding caused higher SOD, CAT, and POD activity than did cutting. Elevated CAT activity tended to remain longer while POD activity rapidly declined after reaching peaks induced by larval feeding. The rapid increase of antioxidant defense enzyme began only after the degree of tissue damage exceeded certain threshold levels, and there was a limitation in the amount of enzyme activity supplied when the damage exceeded endurance of seedlings. Changed SOD, CAT, and POD activities in L. gmelinii were probably defensive responses to tissue damage caused by herbivore feeding or cutting of needles. The effects on SOD, CAT, and POD under different treatments on larch plants were more complicated than expected and need further clarification.