The effects of altering alternative respiratory pathway capacity on salicylic acid (SA)-induced resistance to potato virus X (PVX). Plants were pre-treated by spraying with a solution of SA or a control solution for four days prior to inoculation with PVX. Samples from the fourth leaf above the directly PVX-inoculated leaves of plants were harvested at 28 days post-inoculation and processed for an enzyme-linked immunosorbent assay using anti-PVX coat protein serum. Mean accumulation (μg PVX per gram of leaf tissue) was determined using a standard curve and the data from one experiment, out of a total of three independent experiments, are plotted above. The number of samples was six for each plant line (one sample = one plant) in each treatment group. Error bars represent mean ± standard error of the mean. Accumulation of virus was significantly different between non-transgenic and AOX 3 Aox-transgenic plants (p = 0.044) and between SA-treated and SA-treated AOX3 Aox-transgenic plants (p = 0.020). Mean titer values labelled with the same lower case letter were not significantly different from each other (t-test, p > 0.05).