Figure 8.

Effects of cold stress on eATP concentrations and eATP inhibition of cell viability in wild-type (WT) and PeAPY2-transgenic lines. T3 seeds of wild-type and PeAPY2-transgenic lines (OE2 and OE4) were germinated on one-half-strength MS medium. A, Seven-day-old seedlings of all tested lines were subjected to 4°C for 7 d (cold stress), followed by −1°C for 12 h and 4°C for 12 h, and were finally returned to 22°C for 12 h of recovery (R12h). [eATP] was measured in extracellular root medium. Each point is the mean of three independent experiments, and error bars represent se. **, P < 0.01, wild-type versus PeAPY2-transgenic lines. B, eATP inhibition of cell viability. Seven-day-old seedlings of wild-type and PeAPY2-transgenic lines (OE2 and OE4) were treated with 0 or 800 μm ATP for 12 h. Equal molar values of CaCl₂ were applied for the ATP treatment, and pH was adjusted to 5.7 to 5.8 when ATP was added into the nutrient solution. Root cell viability was assayed with FDA (green) and PI (red) staining. The merged images show the double staining. Three independent experiments were performed, and representative images are shown. Bars = 250 μm.