Figure 5.

Effect of MV on wild-type and FNR-expressing plants. A, Typical leaf injuries caused by exposure to MV. Four-week old wild-type and transgenic plants were sprayed with 100 μm MV in 0.05% (v/v) Tween 20, and pictures were taken after 3 d of incubation under growth chamber conditions at 150 μmol quanta m⁻² s⁻¹. The pFNR-3 specimens employed contained 3.5-fold more reductase than wild-type controls. B, MV-induced pigment degradation. Leaf discs from 6-week-old plants were placed on solutions of the indicated concentrations of the herbicide and illuminated at 500 μmol quanta m⁻² s⁻¹ and 25°C during 12 h. Chl (squares) and carotenoids (circles) from wild-type (black symbols) or pFNR-3 (white symbols) plants were determined after MV treatment. Percentages of the initial values are shown. C, MV-induced membrane damage. Ion leakage was estimated by measuring the increase in conductivity of the medium after MV treatment of leaf discs from 6-week-old wild-type (triangles), pFNR-1 (diamonds), and pFNR-3 (squares) plants. White symbols correspond to discs infiltrated with water. In B and C, asterisks indicate significant differences between transgenic and wild-type plants by ANOVA (P < 0.05). The pFNR-1 and pFNR-3 specimens employed contained 1.4- and 5.1-fold more reductase than wild-type controls. D, Effect of MV poisoning on the maximal quantum yield (φ_PSII) of PSII. The φ_PSII parameter was measured on the fourth fully expanded leaf, 5 h after spraying 4-week-old plants with 100 μm MV and before any visible damage could be detected. E, Oxidative cleavage of Rubisco LSU in plants treated with MV. Extracts were prepared from the fourth fully expanded leaf of 4-week-old plants sprayed with 100 μm MV or mock solution and incubated for 3 d under growth chamber conditions at 150 μmol quanta m⁻² s⁻¹. Samples corresponding to 2 mg fresh leaf weight were fractionated by SDS-PAGE and blotted onto nitrocellulose membranes for immunodetection with LSU antisera.