| Larix gmelinii is main specie of forest in northeast area of China. It was selected as object for research in this paper, in order to avoid destructiyeness disaster of L. gmelinii caused by D. superans reoutbreak, which resuting more economic damage; and searching effective meansure to manage pest was primary task. After L. gmelinii seedlings were cut or D. superans fed, the activities of resistant enzymes with the sequence of time changing in L. gmelinii were measured by UV-spectrometry bioassays, presented specific results.1,The activities of defensive enzymes in L. gmelinii seedlings under the stresses of cutting needles and herbivore feedingPhenylalanin ammo-nialyase (PAL) and Polyphenol oxidase (PPO) were defensive enzymes that contribute to the defensive responses in plants. The activities of defensive enzymes in intact needles of L. gmelinii seedlings were intensively induced by cutting or feeding 50 % of four branches, and sustained for a long time. The activities of PAL caused by D. superans were not significantly different with cutting needles when injured degree was 50 % of four branches. In contrast, D. superans caused more intensive PPO increases than cutting needles, but the tendency of the change in activities of defensive enzymes that induced by D. superans were similar to cutting needles, the highest activities of defensive enzymes caused by above two treatments were observed at the same time.2,The activities of antioxidant enzymes in L. gmelinii seedlings under the stresses of cutting needles and herbivore feedingPlant antioxidant enzymes are the important substances in induced defensive responses of plant. The activities of antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), in seedlings under the stresses of cutting needles and feeding were compared. The results showed that three kinds of antioxidant enzymes activities were changed significantly. Activities of antioxidant enzymes didn't changed with the injured degrees. While under the same injured degree, the maximum activities of antioxidant enzymes appeared at the same period that was induced by these two treatments, and under 25 % of four branches injured degree cutting needles caused the less intensive antioxidant enzymes than D. superans feeding, but inductions of SOD, POD and CAT activities were not signiffcantly different under 75 % of four branches injured degree. Sustaining time of SOD caused by cutting needles and D. superans feeding were not signiffcantly different, but D. superans feeding caused longer sustaining time of CAT activities, and sustaining time of POD activities compared with cutting needle. This phenomenon was closed interrelated with their function in defense response. 3,The activities of proteinase inhibitors in L. gmelinii seedlings under the stresses of cutting needles and herbivore feedingPlant proteinase inhibitors (PPIs) are important defensive substances. We observed that after the seedling needles were cut with scissors or fed by the larvae of Dendrolimus superans. The results showed that both TI and CI activities in the seedling needles increased significantly after treated from one to twenty days, compared with control. However, there was no significant relationship between PI activities and the damage degrees. TI activities induced by insect feeding were higher than that by cutting needles under the same injured degree whereas the differences were not significant. CI activities induced by larva feeding were all higher than that by cutting needles only at the 5th day no matter what damage degrees.Our results clearly demonstrated that the caterpillar feeding and mechanical wounding resulted in the same inducible defensive system, but response intensity of plants was different to these two treatments. D. superans feeding and cutting needles could induce plant defensive responses which suggested a new method to pest control of making appropriate injury intentionally to mimic well the effects of herbivory attack in order to increase plant defences.
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