In order to investigate the transportation and distribution of salicylic acid (SA) from root to aboveground tissues in response to high temperature, the roots of grape plant were fed with 14C-SA before high temperature treatment. Radioactivity results showed that progressive increase in SA transportation from root to aboveground as compared with the control varied exactly with the heat treatment time. Radioactivity results of leaves at different stem heights indicated that the increase in SA amount at the top and middle leaves during the early period was most significant in comparison with the bottom leaves. The up-transportation of SA from root to aboveground tissues was dependent on xylem rather than phloem. Auto- radiographs of whole grape plants strongly approved the conclusions drawn above. Root-derived SA was believed to be a fundamental source in response to aboveground high temperature.
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.
LIU YanPAN Qiu-hongZHAN Ji-chengTIAN Rong-rongHUANG Wei-dong
