Figure 3.

Biological activity correlates with ability to prime for stronger PAL gene activation. Arabidopsis plants were pretreated for 3 d with the indicated SA derivatives at 300 μm, with BTH at 100 μm as a positive control or with the wettable powder carrier only (control). The leaves were then left untreated (−), slightly squeezed with forceps (+), or infiltrated with water (+). After 2 h, PAL gene activation was monitored by RNA gel-blot analysis. Equal sample loading was confirmed under UV light by visualization with ethidium bromide (not shown). 3-HBA, 3-hydroxy-benzoic acid; 3,5-DCSA, 3,5-dichloro-SA.