Ethylene pretreatment and blackspot of potato tubers, Solanum tuberosum: Histochemistry and histology of wound healing

Summary Potato tubers preconditioned by exposure to 1–2 μ liter ethylene/liter for 72 hours, undergo different wound-healing responses after bruising than the tubers exposed only to air. Cytological evidence for an enhancement of cell division and starch hydrolysis, and histochemical evidence for a greater accumulation of RNA and protein was obtained. Procambial development is also enhanced, but the development of a suberized periderm is greater in the air controls. After incision wounding, evidence of cell division leading to periderm formation was observed much earlier in the ethylene pretreated tubers than in the air controls. These responses to wounding are an indication that pretreatment with ethylene causes changes in the tissue that minimize the activity of enzyme systems such as polyphenoloxidase that lead to darkening. The marked increase in RNA and protein in the ethylene pretreated tubers supports the assumption that the amino acid and phenolic substrate, tyrosine, may be utilized in protein accumulation and thus becomes unavailable for oxidation into the dark phenolic products resulting in blackspot.