FIGURE 6.

Stimulation of A. thaliana growth and salt tolerance by individual volatile compounds and a volatile blend emitted by P. phytofirmans PsJN. Root growth, rosette area and fresh weight were determined for A. thaliana col-0 grown in vitro on MS¹/₂ agar medium without bacterial inoculum, placed in front of an independent MS¹/₂ agar plate inoculated with 1 × 10⁶ CFU/ml of P. phytofirmans (PsJN-VOCs), non-inoculated MS¹/₂ agar (N. I.), or in the presence of different amounts of volatile compounds added per plate. Tested compounds were 100 ng of 2-undecanone (2-UN); 1-heptanol (1-HP); 3-methyl-butanol (3-MB); or a 1:1:1 blend of the three compounds (BLEND). Plants were transferred at 14 DAS to fresh MS¹/₂ agar with no added NaCl or CaCl₂ (untreated controls) (A), or MS¹/₂ agar with 150/15 mM NaCl/CaCl₂ (B). Growth parameters were registered at 21 DAS. Columns show mean values relative to N. I. controls, and the error bars indicate standard deviations from experiments with 24 plants analyzed for each compound treatment. Asterisks indicate statistically significant differences from the control (N. I.) treatment within each compound (One way ANOVA Tukey’s HSD tests; p < 0.05).