Studies On The Mechanisms By Which Elevated CO₂ Affects Interaction Between Two Color Morphs Of Acyrthosiphon Pisum Harris And Their Host Vicia Faba

Increasing attention has been focused on the elevated global atmospheric CO₂ concentration,especially on the effect of elevated atmospheric CO₂ concentration on insects and their hosts.In this study,two elevated levels of CO₂ concentration（moderate:550±27 μL/L;doubling:750±37 μL/L）were manipulated in incubators with ambient CO₂（375± 18 μL/L）as the control.Vicia faba seedlings were planted in the above incubators,nymphs of the pea aphid within 6 h were introduced later,and molting and the survival in various developmental stages were recorded until the adult.Effects of elevated CO₂ concentration on the survival rate,developmental duration,reproduction,life table parameters and other biological characteristics of red and green morphs of the pea aphid in three successive generations were studied to clarify the changes of the population of two morphs of pea aphids under the elevated CO₂.Nutrient contents,digestive enzyme and transaminase activities of two color morphs of the pea aphid in three successive generations and nutrient and secondary compounds contents in V.faba leaves were assayed.Also,Correlation analysis between developmental and reproductive performances of two color morphs of pea aphid and nutrient and secondary compounds contents in V.faba leaves were conducted.Original conclusions were obtained as following:1.Effects of elevated CO₂ on development and reproduction of the three successive generations of two color morphs pea aphids Acyrthosiphon pisumIt was found that developmental duration of three consecutive generations of two color morphs of pea aphid was shorten,while larval weight,adult weight,weight difference and mean daily relative growth rate all displayed increasing trends under the elevated CO₂ conditions.Also,the reproductive period was prolonged,and the average and maximum fecundity of larvae were both increased.Net reproductive rate（R0）of three consecutive generations of two color morphs of pea aphid were increased and generation time（T）pronged,While intrinsic rate of increase（rm）and finite rate of increase（λ）were decreased.The population of two color morphs of pea aphid declined under the elevated CO₂ conditions.Hence,elevated CO₂ may have negative effects on pea aphid population numbers.2.Effects of elevated CO₂ on nutrient and secondary compounds contents in leaves of V.faba in different damaged levels by pea aphidElevated CO₂ concentration significantly enhanced the contents of soluble protein,soluble carbohydrates,free amino acids and starch in V.faba leaves.It may be due to symbiotic nitrogen fixation function of legumes,making it easy to adapt to high concentrations of CO₂ on the demand for nitrogen.Flavone content in V.faba leaves in different damaged levels by pea aphid was not change under the elevated CO₂,while phenolic,simple phenols,tannin and total saponin all displayed increasing trends.3.Correlation analysis between development and reproduction of two color morphs of pea aphid and nutrient contents in V.faba leaves in elevated CO₂Elevated CO₂ concentration significantly changed the contents nutrient and the biological parameters of pea aphid.There was a significant negative correlation between the developmental duration in F2 generation of the two color morphs of the pea aphid and the soluble protein,soluble sugar,free amino acid and starch content in V.faba leaves,and positive correlation between the adult weight,the average and maximum fecundity of larvae and nutrients.While intrinsic rate of increase（rm）and finite rate of increase（λ）in F2 generation of the two color morphs of the pea aphid were negatively correlated with the nutrients in V.faba leaves,generation time（T）was positively correlated with the nutrients,and net reproductive rate（R0）in F2 generation of green pea aphid and doubling time（t）of red pea aphid were positively correlated with the nutrients in V.faba leaves.4.Correlation analysis between development and reproduction of two color morphs of pea aphid and secondary compounds of contents in V.faba leaves in elevated CO₂There was a significant negative correlation between the developmental duration in F2 generation of the two color morphs of the pea aphid and the phenolic,simple phenols,tannin and total saponin contents in V.faba leaves in elevated CO₂.and positive correlation between the adult weight,mean daily relative growth rate,the average and maximum fecundity of larvae and the phenolic,simple phenols,tannin and total saponin.While intrinsic rate of increase（rm）and finite rate of increase（λ）in F2 generation of the two color morphs of the pea aphid were negatively correlated with the phenolic,simple phenols,tannin and total saponin contents in V faba leaves.Net reproductive rate（R0）,generation time（T）and doubling time（t）were positively correlated with the phenolic,simple phenols,tannin and total saponin contents in V faba leaves.Also the biological and life table parameters of the pea aphid had no correlation with the flavone content in V.faba leaves.5.Effects of elevated CO₂ concentration on the nutrient contents in two color morphs of the pea aphids Acyrthosiphon pisumThe content of protein,total amino acid,soluble carbohydrate and glycogen in three consecutive generations of two color morphs of pea aphid displayed increasing trends and total lipid and free fatty acids decreased significantly under the elevated CO₂ conditions.Under the moderate CO₂ concentration（550±27 μL/L）condition,the nutrient contents in F0 generation of the two color morphs of the pea aphid had no significant difference as compared with the control,while the contents of protein,total amino acids,soluble carbohydrates and glycogen in F2 generation all increased and the contents of total lipid and free fatty acids decreased significantly,and moreover the content of soluble carbohydrates in F2 generation of green pea aphid was significantly higher than that in red pea aphid.Under the doubling CO₂ concentration（750±37 μL/L）condition,the contents of protein,total amino acids,soluble carbohydrates and glycogen in three successive generations of the two color morphs all increased significantly and the contents of total lipid and free fatty acids decreased significantly as compared with the control,and moreover,the contents of protein,total amino acids,soluble carbohydrates and glycogen in the F1 and F2 generations of green pea aphid were significantly higher than those in red pea aphid.6.Effects of elevated CO₂ concentration on digestive enzyme and transaminase activities in two color morphs of the pea aphid,Acyrthosiphon pisumThe activities of pepsin and trypsin in three consecutive generations of two color morphs of pea aphid decreased significantly and those of lipase and amylase increased and AST,ALT and GS decreased significantly under the elevated CO₂ concentration.Under the elevated CO₂ concentration（550±27and 750±37 μL/L）conditions,the digestive enzyme and transaminase activities in F0 generation of two color morphs of the pea aphid had no significant difference as compared with the control,while the pepsin and trypsin activities in F2 generation decreased significantly and those of lipase and amylase increased and ALT,AST and GS decreased significantly,and moreover the digestive enzyme and transaminase activities had no significant difference between the two color morphs.