| Larch(Larix olgensis)mainly distributed in Northeast China and Inner Mongolia forest region is one of main forest species in Northeast china.In order to avoid the huge economic loss to the artificial forest caused by the rampant occurrence of defoliators such as Dendrolimus superans and Lymantria dispar,we must seek effective defense measures to protect this important species.In this paper,we used larch(Larix olgensis)forest and larch-ash(Manchurian ash)mixed forest as the research object to investigate the effects of larch-ash mixed forest and different mixed forest type of young forest on systemic induced resistance of Larix olgensis by using UV Spectrophotometry to measuring the activity of defense protein enzymes and protease inhibitor and the content of secondary metabolites in larch needles of different mixed forest type.1.Effect of different mixed forest types of Larch-Ash on the activity of defensive enzymes in Larch needlesThe results showed that the activity of several defense proteinsin larch needles of HJ30(4:4),HJ20(4:4)and3-year-old mixed forest significantly increasedcompared with that of larch-forest(P<0.05).In larch needles of HJ20(4:4)in Zhangjiawan,the activity of PPO,PAL were the highest,as well as the activity of PPO and PAL were higher than that in larch needles of HJ20(2:10)(P<0.05).2.Effect of different mixed forest types of Larch-Ash on the activity of protease inhibitors in Larch needlesThe protease inhibitors were significantly higher in different mixed forest types than those of Larch(p<0.05).In 20-years-old mixed forest,HJ20(4:4)Larch needles had the highest TI activity,which was higher than HJ20(2:10),but the difference was not significant;the CI activity of HJ20(2:10)Larch needles was significant higher than that of HJ20(4:4)(p<0.05);in the young growth of mixed forest,there were significant differences in different mixed forest types of induction in different times(p<0.05),the TI and CI activities in the mixed plantation needles reached the maximum value in August 22nd.The TI and CI activities were highest in the Larch needles of HJ3:3,and the TI activities was significant higher than that in HJs:5(p<0.05).The result were consistent between the potting and the mixed plantation.3.Effects of different mixed forests types of Larch-Ash on contents of secondary metabolites in Larch needlesThe content of secondary metabolites in Larch needles of different mixed forests types was significantly higher than that of the control(p<0.05).In 20-year-old mixed forests,the content of flavonoids and lignin in larch needles of HJ20(4:4)were the highest,among them the content of lignin was significantly higher than that in HJ20(2:10),and the tannincontentin HJ20(2:io)did not significantly added(P>0.05)in contrast to that in needles of HJ20(4:4).For two different treatments on mixed forests,the content of flavonoids and tannin in mixed plantation forest showed the first increased and then decreased tendency,the lignin content increased continuously with time,and reached the maximum in September 1st.Besides,in different mixed plantation forest,the contents of secondary metabolites in the needles of HJ3:3and HJs:5 were significantly higher than that in HJ1:1(p<0.05);the lignin contentin the mixed potting forest were similar to those inthe mixed plantation forest,moreover,the content of tannin in the needles of HJ3:3 were significantly higher than thosein HJ1:1 and HJ5:5(p<0.05),and between August 1st and September 1st,the content of flavonoids in the needles of HJs swere the highest.In conclusion,these results indicate that larch-ash mixed forests significantly strengthen the activity of defense proteins and increase the content of secondary metabolites in larch needles,and then which improve the larch resistance to defoliators.Compared with HJ20(2:10),the induced defense of HJ20(4:4)is stronger.In the young forest,HJ3:3and HJ5:5induced defense ability stronger than HJ1:1.so that,the results provide a theoretical basis for the prevention and control of larch-ash 3-5 rows mixed with narrow band. |
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