Insect Footsteps on Leaves Stimulate the Accumulation of 4-Aminobutyrate and Can Be Visualized through Increased Chlorophyll Fluorescence and Superoxide Production

A substantial literature has demonstrated that within 2 to 3 h of insect herbivory or mechanical damage, plants synthesize wound-induced proteinase inhibitors that inhibit digestion ([Bergey et al., 1996][1]; [Ryan, 2000][2]). In contrast, we demonstrate here that the simple non-wounding crawling of