Figure 6.
Polyamine oxidase activity in planta and effects of its suppression. A, Polyamine oxidase activity in apoplast. Apoplastic fluids from leaves inoculated with TMV (black bar) or mock (white bar) were extracted at the indicated time period after temperature shift (h) and were subjected to polyamine oxidase activity assay. The concentration of hydrogen peroxide generated in the reaction containing 10 μL of apoplastic fluid and either 5 mm spermidine (left panel) or 5 mm spermine (right panel) was estimated. Average values and sds are from three independent experiments, each with one individual sample. Experimentally measured values were statistically tested and confirmed to be P ≤ 0.02. B, Inhibition of necrotic lesion formation by polyamine oxidase inhibition. Detached leaves were treated with 10 mm guazatine 12 h before temperature shift. Lesions developing 24 h after temperature shift in the absence (water) and presence (guazatine) of the inhibitor are shown in the panels.