Abstract
Salicylic acid (SA) is a proposed signal for systemic acquired resistance to pathogen infection, while precise mode of SA translocation is little understood. To study it directly, 14C-SA was fed to the petiole end and the signal was detected autoradiographically. In juvenile plants, the signal moved to the lower stem and root, then the vascular systems of upper, middle and lower leaves within 1 h. In adult plants with 13 developed leaves, it was detected in nodes of 6 upper and 3 lower leaves at 10 min, and all leaves at 1 h along the orthostichy of phyllotaxis after feeding from the 7th leaf. The signal dispersed to the leaf gap, cortex parenchyma, and epidermis. One and 7% of radioactivity recovered was detected as SA β-glucoside at 10 min and 1 h, respectively. Thus, SA can move rapidly at all nodes of plants as an emergency signal within 1 h.
