Toxic Effects Of Secondary Metabolism Changes Of Common Ragweed Under CO₂ And Heat Wave Stress On Ophraella Communa

Biological control can effectively save resources and prevent environmental pollution.The global greenhouse gas concentration continues to rise,the greenhouse effect is becoming more and more serious,and the accompanying heat wave events occur frequently.The Ophraella communa blong to Chrysomelidae,Coleoptera,which is an effective biocontrol insect against common ragweed.Some researches have shown that high concentrations of CO₂can promote plants to produce secondary metabolites that are defensive to insects,and heat waves can eliminate this induced effect.To explore the effects of CO₂and heat wave on O.communa,this paper used high concentration of CO₂and heat wave,and the indirect effects of this change on the physiological metabolites and growth and development of the O.communa.The changes of growth and development of O.communa after fed with high concentration of CO₂and heat wave threat were studied.And the changes of metabolites in common ragweed with high concentration of CO₂and heat wave treatment were analyzed.The higher expressing metabolites were selected for bioassay of O.communa.The results provided preliminary theoretical and data support for the subsequent study of the metabolic relationship and nutritional relationship of common ragweed and O.communa.The main results are as follows:1 Effects of high concentration of CO₂and heat wave treated ragweed on metabolites of ragweedAfter high concentration of CO₂and heat wave treatment,there were 163metabolites changed significantly in the two groups.Among them,88 substances were significantly up-regulated and 75 metabolites were significantly down-regulated.The top ten substances with significant increase in content include tryptamine and its derivatives,carbohydrates,quinic acid and its derivatives,flavonoids,isoflavones,organic acids and their derivatives,and amino acid derivatives.KEGG pathway enrichment of differentially metabolized products showed that significant pathways were more then 20 metabolic pathways such as terpenoids and steroids biosynthesis pathway,isoflavones biosynthesis pathway,aro-matic compounds degradation pathway,tyrosine metabolism pathway,steroid hormone biosynthesis pathway,steroid degradation pathway,serotonin receptor agonist metabo-lism pathway,polycyclic aromatic hydrocarbon reduction pathway,catabolic pathway.2 Effects of high concentration of CO₂and heat wave treated ragweed on the development and reproduction of O.communaWhether or not common ragweed is treated by heat wave,after feeding common ragweed with high concentration of CO₂treatment,the developmental stages of first-instar larvae,larval stage,pupa and immature larvae of O.communa were significantly prolonged,the survival rate of pupa was significantly reduced,and the longevity of adults was significantly shortened and the egg production decreased.The life table of O.communa showed that after feeding the ragweed treated with high concentration of CO₂and heat wave,the intrinsic rate of increase and net reproduction rate of the population of the O.communa were significantly reduced,and the generation time was significantly prolonged,but the finite rate of increase of population has not been affected much.Feeding on ragweed treated with high concentration of CO₂had adverse effects on the growth and population reproduction of O.communa,and the heat wave treatment promoted the adverse effects caused by high concentration of CO₂.3 Effects of high concentration of CO₂and heat wave treated common ragweed on the enzyme activity of O.communaAfter feeding on common ragweed grown under high CO₂concentration,the activity of peroidase,superoxide dismutase,acetylcholinesterase,carboxylesterase,trypsinase and lipase increased significantly,while the activity of pepsin decreased significantly,and the result show that heat wave can promote this effect.The comparison of enzyme activity between males and females showed that the enzyme activity in females was higher than that in males,high concentration of CO₂and heat wave had no significant effect on this relationship.4 Effect of feeding 8 metabolites on O.communaThe mortality rates of larvae and immature stages were significantly higher than those of controls group after feeding on 4-O-caffeoylquinic acid and cinnamyl pentahydroxytryptamine at four different concentration gradients.There was no effect on oviposition rate,female ratio,adult longevity and adult body weight.The other six substances had no significant effect on the larvae.In summary,high concentration of CO₂and heat wave can significantly affect the metabolism of common ragweed,which can be transmitted to the O.communa through their feeding on ragweed,causing changes in physiological metabolism,development and reproduction of the O.communa,the reason for this change may be that high concentrations of CO₂and heat wave treatment increase the content of secondary metabolites in ragweed that are unfavorable for the growth and development of O.communa.The above research results provide a new theoretical basis for the better use of the O.communa for the prevention and control of common ragweed.