Abstract: Abstract: Effects of mechanical wounding on endogenous salicylic acid (SA) and jasmonic acid (JA) were investigated in pea (Pisum sativum L.) leaves. The results showed that endogenous JA rapidly accumulated within 30 min after wounding and then significantly decreased, which is called “JA burst”. The increase in the activities of both lipoxygenase (LOX) and allene oxide synthase (AOS) lagged behind JA burst. A second slight increase in JA level was observed at 24 h after wounding treatment, and at this moment, higher activities of LOX and AOS also were detected. Endogenous free SA content decreased accompanying with JA burst. Effects of exogenous JA application were similar to these 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 JA level at the early stage of treatment. It is thus suggested that JA 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.

Key words: Salicylic acid, Jasmonic acid, Mechanical wounding, Pea leaves