Response Mechanism Of Secondary Metabolism Defense System In Artemisia Frigida Willd. To Mechanical Damage

To investigate the effects of feed intake and trample damage on secondary metabolism of Artemisia frigida Willd., A. frigida taken from Inner Mongolia grassland was potted in the laboratory and treated with different degrees of mechanical damage(light, moderate, severe damage treatments and control group). After treatments, the content of membrane fatty acid, phenolic acids, tannins, flavonoids and total phenolic, the activity of LOX, PPO and PAL, ingredients of water extracts from leaves and roots of A. frigida was measured. The study also analyzed the changes of each index with the sequence of time changing under different levels of mechanical damage. The results of this test are as follows:1. Eight kinds of fatty acids was found both in leaves and roots membrane lipid of Artemisia frigida by GC-MS analysis. Unsaturated fatty acids accounted for most of the lipid, but there are slight differences in the composition. Damage-induced saturated fatty acid(palmitic acid) content of A. frigida increased, and content of unsaturated fatty acid(linolenic acid, linoleic acid and docosadiyndioic acid) decreased. After mechanical damage treatment, the activity of LOX in leaves and roots of A. frigida increased and reached the peak at 24 h.2. There were eight kinds of phenolic acids detected from all the groups. They are gallic acid, protocatechuic acid, chlorogenic acid, caffeic acid, clove acid, p-coumaric acid, ferulic acid and cinnamic acid. Damage induced the content increase of the other seven kinds of phenolic acid in A. frigida except chlorogenic acid. And most of them reached the peak at 12 h. The content of free phenolic acid(protocatechuic acid and ferulic acid) increased significantly, and the response of leaves was more rapid than that of roots.3. After the damage treatment, the content of total phenols and flavonoids in A. frigida increased gradually at the level of different kinds of degree of mechanical damage; with the time changing it increased at first and then decreased. The content of tannin in leaves increased with treatment time changing, the tannin content in roots increased at first and then decreased. After moderate and severe damage treatments, the changes of its content were more obvious then light damage treatment.4. PPO and PAL are important defense enzymes in plants, the changing of there activity marks the changing of chemical defense system of plants. Dealing with different degrees of mechanical damage strongly induced the activity of PPO and PAL in leaves and roots of A. frigida. The induction of PPO activity responded quickly, and it reduced significantly at the late-damaging period.5. The main components of water extracts of A. frigida were terpenes. Phenols, alcohols, aromatics and ketones were also detected. After damage treatments, the total amount of components of water extracts increased within a certain time range. In light damaging group, it increased more slowly and peaked late; after treatment of moderate and severe damage, it increased rapidly and reached a peak at 6h, then declined; with light and moderate damage the types of composition of extracts increased while it decreased in severe damaging group. The content of terpenoids in damage treated groups increased significantly compared with the control group. In particular, the increasing trend of 8-Hydroxylinalool was the most obvious.In this paper, through the study of membrane fatty acid content, LOX activity, products content of secondary metabolites and defense enzymes activity of A. frigida with varying degrees of mechanical damage showed that the biological membrane system of A. frigida was damaged after damage treatments, stress response in vivo was activated, the activity of defense enzymes was induced increasing rapidly, then it regulated the expression and accumulation of secondary metabolites to produce an response to stress factors and an increase in resistance. The response mechanism of secondary metabolism defense system in A. frigida to mechanical damage was explored. The study provided new data and theoretical basis for revealing the resistance of A. frigida to grazing and the reason why A. frigida has become an important protector in grassland ecological environment.