Differences Of Larch Resistance Chemicals Under Different Ages Or Pedigree And Hybrid Families

Larix spp. is one of the main trees which reserving water and soil in the North, boradly distributed in China, whereas, in recent years they are always suffered serious pests and diseases, who greatly affect the normal growth of tree, resulting in serious economic losses. At present, much have been done in the field of chemical control to larch, but lack the research on relationship, that between stand age or family and pest or disease control in the view of chemical ecology or plant physiology or ecology.This article studied the influences of different ages and different families on defensive substance, including the contents of tannin and phenolic acid, the activities of protective enzymes, defensive enzymes and proteinase inhibitor. Larix olgensis and L. kaempferi×L. gmelinii were divided into three age groups:young forest (aged from 1-20 years), middle-aged forest (21-30 years), near-mature forest (31-40 years). The L. olgensis needles were sampled from two families,73-26 and 73-28, at the ages of 16,19,22 and 37 years. The hybrid larch needles were sampled from two families, L. kaempferi 5×L. gmelinii 9 and L. kaempferi 3×L. gmelinii 2, at the ages of 17,19,22, and 30 years. The objective was to improve protection measures for larch resources and to effectively control the risk of forest degradation due to pests and diseases, and to choose the better tree to plant. The results showed as follows,1 Differences of larch resistance chemicals under different stand agesThe contents of tannin in different ages have been analyzed by using vanillin-HCL assay. 10 kinds of phenolic acids were recognized with the method of HPLC, gallic acid, salicylic acid, benzoic acid, vanillic acid, caffeic acid, syringic acid, cinnamic acid, coumaric acid, chlorogenic acid and ferulic acid. The activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), phenyllalanine ammonia lyase (PAL), polyphenlo oxidase (PPO), trypsinin-hibitor(Tl) and chymotrypsin inhibitor (Cl) were tested with the application of UV-spectrophotometric method. The result indicated that, the contents (activities) of resistance chemicals mainly showed young forest>middle-aged forest>near-mature forest.2 Differences of larch resistance chemicals under pedigree and hybrid familiesThe contents of condesend tannin in hybrid larch were higher than in Larix olgensis. Phenolic compounds in Larix olgensis 73-28 were markedly higher at the young forest, while hybrid larch was higher at the middle-aged forest. The activities of POD, CAT and SOD in Larix olgensis were higher than hybrid larch (June and July), especially at the middle-agde forest, while hybrid larch were higher in August. The activities of protein enzymes in Larix olgensis (pedigree) had strong resistance, while hybrid larch showed their advantage only during a short time at the young and middle-aged forest. 3 Differences of larch resistance chemicals under different growth periodsThe contents of condesed tannin most showed July>August>June, and there were evidently different among the months. The activities of protective enzymes were different among three growth period, but there was no obvious difference. POD, SOD, PPO, TI and CI most showed June>July>August, CAT showed July>August>June, PAL in August was higher.The results evidented that stand age and family evidently affected the expression and accumulation of defensive substance in larch needles (P<0.05), and the growth period was also the important factor. The paper was the first and systematic study, which research the connection between stand age, family or growth period and plant defense capability. The results will house the department of scientific management and breeding good larch trees, and provide a new theoretical basis for ecological control on larch pests, thus reduced the chemical damage to the environment, in order to maintain ecological balance. However, in this study, there were no significant rules between the contents (activites) of defense substances and growth period (month), which may be related to the weather conditions of sample collection and tree species characteristics, so it need further exploration on weather conditions and relationship of parent and the hybrid offspring, and add the biometric resistance of larch, in order to provide a more reliable theoretical basis.