Feeding behavioral response of cotton aphid, A phis gossypii , to elevated CO 2 : EPG test with leaf microstructure and leaf chemistry

Effect of elevated CO 2 on feeding behavior of the cotton aphid, A phis gossypii ( G lover) ( H emiptera: A phididae), was investigated using electrical penetration graphs ( EPG ) on cotton, G ossypium hirsutum L. ( M alvaceae). Leaf microstructures and foliar soluble constituents were also measured simultaneously to quantify the impact of foliar changes on leaf nutritional quantity and quality, owing to elevated CO 2 , on stylet penetration and food‐quality plasticity of A . gossypii . Significant increases in fresh body weight, fecundity, and population abundances of A . gossypii were found in elevated CO 2 in contrast to ambient CO 2 . Elevated CO 2 influenced the feeding behavior, as evidenced by altered EPG recordings, including the increased non‐penetration period (walking and finding the feeding site), E2 <8 min (probes with sustained ingestion of <8 min), and first E2 >8 min (first occurrence of probes with sustained ingestion of >8 min), and decreased E2 >8 min recordings. Moreover, leaf microstructures were significantly affected by CO 2 levels, with thinner upside epidermis ( UPE ) and thicker underside epidermis ( UDE ), sponge tissues ( ST ), and fence tissues under elevated CO 2 compared to that in ambient CO 2 . Therefore, it is expected that A . gossypii spend more time penetrating the thicker leaf UDE and ST when the host plant is exposed to elevated CO 2 . Furthermore, elevated CO 2 significantly enhanced foliar soluble matter, including soluble sugars ( SS ), free amino acids and fatty acids ( FFA ), and total soluble matter ( TSM ), which was congruent with significant increase or decrease in leaf turgor or osmotic potential. Increased leaf turgor and leaf soluble constituents favored ingestion in A . gossypii , resulting in increases in fresh body weight, fecundity, and population abundances under elevated CO 2 . These feeding behaviors and resulting population growth parameters are consistent with the significant positive correlations between aphid fresh body weight and foliar FFA / TSM , between A . gossypii fecundity and foliar SS of cotton plants, and between the time of E2 <8 min recordings and leaf turgor.