Effects of aphids Myzus persicae on the changes of Ca2+ and H2O2 flux and enzyme activities in tobacco

In order to understand the continuous defense reactions of host plants against insect attack, a tobacco variety G140 was infested by tobacco aphid Myzus persicae for 2 h to 5 d. The changes of transmembrane ionic fluxes (Ca2+) and hydrogen peroxide (H2O2) were detected by the technique of noninvasive micro-test and their relationship was further studied. It was found that H2O2 accumulation depended on Ca2+ influx. Ca2+ flux exhibited a strong influx at all infestation periods by aphids, while H2O2 showed an efflux behavior. The slight variation tendency of Ca2+ influx and H2O2 efflux was consistent. The activities of the corresponding defense proteins, peroxidase (POD) and catalase (CAT) enzyme, were enhanced to respond to the insect attacks, much higher than those tobacco in control. The Ca2+ influx and H2O2 efflux, as well as the activities of POD and CAT enzymes, were increased in a long period of aphid feeding. It indicated that a continuous physiological response of tobacco to aphid infestation could be initiated and lasted for a long time.