Interactions between aboveground and belowground induction of glucosinolates in two wild Brassica species.

•  Interactions between shoot and root induction of glucosinolates in two crucifers, Brassica oleracea and B. nigra, were studied by applying the signalling hormones jasmonic acid (JA) and salicylic acid (SA). •  JA application increased total shoot glucosinolate levels 1.5-3 times, but total root levels did not increase. Only root JA-application yielded a systemic response. In B. oleracea it mattered where JA was applied: root application increased aliphatic glucosinolates in the shoot, whereas shoot application increased indole glucosinolates. Plants treated with JA to both organs had profiles similar to shoot-treated plants. SA-application did not disturb the organ-specific response to JA. Increases in glucosinolate levels did not reduce plant biomass. •  A applications reduced root glucosinolates in root-treated plants. SA root-application in B. nigra resulted in lesions on the leaves and shoot-application caused a trichome response. •  lants thus respond specifically, depending on the organ that is induced and the hormone that is applied. We find a large potential for root-feeders to affect shoot-feeders. Glucosinolate induction in one organ is not constrained by induction in the other organ.