The Effects Of Coning Quantity On Defensive Substance Contents In Larch Needles

Larix spp.is one of the main trees which reserving water and soil in the North,broadly distributed in China,whereas,they are always exposed to forest pests,such as Dendrolimus superans,Coleophora obducta and Strobilomyia spp.,who greatly affect the normal growth of the tree,in which the Strobilomyia spp.took on a predominance damage to the larch in term of the development and growth of the cones and seeds with up to 80%～100%in cones damage and 50%in seeds damage,thus resulted in reduced seed production,poor germplasm and short of resources.At present,much have been done in the field of chemical control to larch,but lack the research on relationship between cone quantities and pest control in the view of chemical ecology and plant physiology and ecology.This article studied the influences of different cones on insect-resistant relevant substances,including the contents of secondary metabolites,the activities of Protective enzymes,defensive enzyme and proteinase inhibitor.The L.olgensis and L.gmelinii were divided into four different grades respectively according to the cones amount,namely,grade I for more cones,gradeⅡfor moderate cones,gradeⅢfor less cones and gradeⅣfor none cones.We discussed the nutrition distribution in the period of cones fruit, the results showed as follows,1.The influences of cones amount to secondary substancesThe contents of tannin in two kinds of tress have been analyzed using vanillin-HCL assay. Both the two kinds of trees indicated an increased tannin contents with the cones decreased, that was,gradeⅠTanninⅠ*Ⅳ<0.0001,P_{TanninⅡ*Ⅳ<0.0001};There seemed to no relevant correlations to species of trees(P>0.05),which proved that constitutive insect-resistant substances in larch were more relative to cones but not species of tress.9 kinds of phenolic acid were recognized with the method of HPLC,namely,benzoic acid, caffeic acid,phenylaetic acid,cinnamic acid,vanillic acid and syringic acid,sylicylic acid, chlorogenic acid and ferulic acid.phenolic acids contents decreased with the cones increased, and significances existed in different cone grades(P<0.05),but had no differences between species of trees(P>0.05).2.The influences of cones amount to activities of protective enzymesWe tested the activities of catalase(CAT ),peroxidase(POD) and Superoxide Dismutase(SOD) with the application of UV-spectrophotometric method.The results indicated that,the activities increased with the cones decreased,that was,gradeⅠ0.05),which proved that constitutive insect-resistant substances in larch were more relative to cones but not species of tress.4.The influences of cones amount to activities of proteinase inhibitorWe tested the activities of trypsinin-hibitor(TI) and chymotrypsin inhibitor(CI) with the application of UV-spectrophotometric method.The results indicated that,the activities of proteinase inhibitor in gradeⅢandⅣwere significant compared with gradeⅠandⅡ(P<0.01).Also,there had no relevant correlations to species of trees(P>0.05).This article indicated that,cones account obviously influenced the express and accumulate of the defensive substances(P<0.05).This is the first time to systematically research the effects of nutrition distribution to plant chemical defense in the process of cones fruiting,which providing a new theoretical basis for larch management and pest control in the period of cones fruiting,and meanwhile,had important roles in ecology maintenance.But in this aritcle indicated that,constitutive chemical defensive substances had little relevance to species of trees(P>0.05) this may be related to the collection of samples and time of the characteristics of tree species,that will needs increase sampling time and sampling varieties for farther research.