FIGURE 7.

Tolerance to methyl viologen of transplastomic tobacco plants overexpressing Trx f or Trx m. 40-day old tobacco plants were sprayed with 30 μM MV and grown in a controlled growth chamber as described in Section “Materials and Methods.” (A) Visual symptoms 2 days after treatment. Photographs show representative plants subjected to the treatment. (B) Maximal photosystem II photochemical efficiency in tobacco plants. F_v/F_m values were measured in plants grown in control conditions (full bars) and in plants subjected to MV treatment for 5 h (dashed bars). Data are mean values ± SD from six plants per genotype. Measurements were performed on two leaves (indicated by arrows in panel A) per plant. **Value significantly different from the value measured in relative non-treated plants with p < 0.01 (t-test). (C) Electrolyte leakage measured on tobacco leaf disks after incubation on 1 μM MV for 14 h at 600 μmol photons m^-2 s^-1. Results were expressed as the percentage of total electrolytes released after treatment relative to that of disks incubated on water under the same conditions. Data are mean values ± SD from three assays. Wt, wild-type; Trx f⁺ and Trx m⁺, plants overexpressing Trx f or Trx m, respectively. **Significantly different from Wt with p < 0.01 (t-test).