Response of Endogenous Salicylic Acid and Jasmonates to Mechanical Wounding in Pea Leaves

The roles of on endogenous jasmonates (JAs) and salicylic acid (SA) in wounding response were investigated. Pea (Pisum sativum L.) seedlings were treated with three different methods including mechanical wounding, JAs application,and SA application. The contents of endogenous JAs and SA, as well as the activities of the related enzymes were detected by enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC), and spectrophotometer, respectively. The results showed that endogenous JA rapidly accumulated within 30 min after wounding. The increase in the activities of both lipoxygenase (LOX) and allene oxide synthase (AOS) lagged behind JAs burst. A second slight increase in JAs level was observed at 24 h after wounding treatment, and at the same time point,higher activities of LOX and AOS were also detected. Endogenous free SA content decreased accompanied with JAs burst. Effects of exogenous JA application were similar to those of wounding treatment on endogenous SA level and phenylalanine ammonia lyase (PAL) activity, whereas exogenous SA application led to the significant inhibition of LOX and AOS activities and the decrease of endogenous JAs level at the early stage of treatment. It is thus suggested that JAs burst and SA decrease in early response to wounding may constitute an important mechanism by which plant starts the related defense reaction and adapts to wounding stress.