The Effect Of Elevated CO₂ And O₃ On The Feeding Behabior Of Two Aphids

Global change,especially the rise in greenhouse gas concentration,has been an item of great concern for the scientific community.Elevated CO₂(O₃) concentration,not only affects the plant growth and development,but also changes the chemical component contents and composition of plant tissues,which indirect impacts herbivore insects,even influences the natural enemies by food chain.In this study,we used closed-dynamics CO₂ chamber(CDCC-1) and open-top chambers(OTC) systematically to study the effects of elevated CO₂(O₃) on the systems of wheat/cotton and herbivory insects(i.e.resistant and susceptible wheats -Sitobion avenae(Fab.),transgenic Bt cotton-Aphis gossypii).The results were as follows:1 The effect of elevated CO₂ on the feeding behabior of Sitobion avenae(Fab.) Two wheat varieties,MY169(susceptible) and KOK1679(resistant) were planted in controlled chambers under elevated CO₂(0.7 mL/L) and ambient CO₂ concentrations(0.35 mL/L,as control) conditions for 30 d.Feeding behaviors of wheat aphids,Sitobion avenae(Fab.),on seedling plants were observed and recorded with electrical penetration graph(EPG).(1) Increased number of potential drop waveform(pd waveform);(2) Prolonged total time of mechanical stylet penetration(total time of C waveform);(3) Delayed initial time of 1st probing from phloem(time to 1st E2 waveform);(4) Extended sustaining time of passive ingestion was observed in S.avenae fed on wheat plants grown under elevated CO₂ than that under ambient CO₂ condition.Our results suggested that the change of feeding behavior of wheat aphids was probably resulted from the change of host plants grown under elevated CO₂ concentration condition.2 The effect of elevated O₃ on the feeding behabior of Aphis gossypiiThe transgenic Bt cotton plants(GK12) were planted in Open-Top Chambers(OTC) under elevated O₃ concentration(1.0×10^-4mL/L) for 30 d,and ambient O₃ concentrations (0.4～0.5×10^-4mL/L) as control.Feeding behavior of cotton aphids,Aphis gossypii,on seeding plants were observed and recorded with electrical penetration graph(EPG).(1) Significantly increased the number of mechanical stylet penetration(C waveform);(2) Advanced initial time of potential drop waveform(pd waveform);(3) Prolonged sustaining time of probing from phloem(E2 waveform) of A.gossypii fed on wheat plants grown was observed under elevated O3 condition than that in control.Our results suggested that elevated O₃ concentration may change the growth,nutritional contents and secondary chemicals of host plants and results in the changes of feeding behavior of aphids.All the studies enriched the theories of the impacts of rising greenhouse gas on the interactions between plant and herbivore insects,and expanded the region of Global Change Biology.It is very important not only on ecological theories,but on integrated pest managements.