Polyamines and wounded storage tissues – Inhibition of RNase activity and solute leakage

The “protective” effect of polyamines and related metabolites on wounded storage tissues was investigated in two experimental systems: RNase activity of potato (Solanum tuberosum L.) tuber discs, and betacyanin leakage from beet root (Beta vulgaris L.) discs. Potato tuber discs evince a dramatic rise in RNase activity 24 h after excision, and this rise is completely blocked by the polyamines, spermidine and spermine. The effect is concentration‐dependent, and several precursors of polyamines are also effective to various degrees in inhibiting the rise in RNase activity. Polyamines inhibit both the wound‐induced RNase and the rise in RNase activity which may result from other senescence‐linked events. Betacyanin leakage from beet root discs is enhanced upon aging of discs and in response to various treatments which may cause membrane damage. Spermidine and spermine effectively inhibit betacyanin leakage which results from aging at 25°C, from incubation at higher temperatures (35–40°C), from freezing of discs, or from treatment of discs with RNase or protease. It is suggested that polyamines decrease RNase activity and solute leakage in sliced storage tissues by affecting primary wound‐induced destabilization of cell membranes.