Fig 1. A plant activator and its effect on Arabidopsis development.

A, The structure of pyrimidin-type plant activator (PPA). B, Determination of a suitable application concentration of PPA. Plants were sprayed with 300 μM BTH (dissolved in 0.3% acetone) or the indicated concentration of PPA (dissolved in distilled water) and 9 days later observed. C and D, Phenotypes of Arabidopsis seedlings grown on 1/2x Murashige and Skoog (MS) plates containing BTH or PPA for 12 days (C) and 20 days (D). E, Comparison of plant biomass with different treatments. Eighteen-day-old plants were treated with 300 μM BTH or 40 μM PPA twice. Twelve days later the fresh weight was measured. F, Effect of plant activators on Arabidopsis root development. Seeds were sown on 1/2x MS horizontal plates and grown for 4 days. Roots of similar lengths were selected and transferred to a 1/2x MS vertical plate containing 300 μM BTH, 40 μM PPA or 0.3% acetone (control). Photos were taken after 5 days. At least fifty independent samples were used for statistical analysis of the length of primary roots (middle panel) and the number of lateral roots per seedling (right panel). Data sets marked with letters indicate significant differences (P<0.05, PLSD-test). The values shown are the averages of three independent experiments. This experiment was repeated three times with similar results, using independent samples.