Hydration-dehydration pretreatment of one-year-old lettuce seeds, employing soaking-drying with or without chemicals or moisture equilibration with a saturated atmosphere followed by drying back, greatly slowed down the deterioration of seeds subjected to accelerated ageing (100% RH and 40°C) after treatment. Introduction of chemicals like potassium iodide (10-4 M), p-hydroxybenzoic aeid (10-4 M) and tannic acid (10-5 M) into the seed by the dry permeation technique, employing acetone as the solvent, effectively controlled seed deterioration. Germination advancement and leaching out of inhibitors from the seed are ruled out as the possible reasons of the beneficial effects of the treatments on the maintenance of vigour and viability. It is suggested that the physico-chemical treatments minimize lettuce seed deterioration by counteracting free radical damage to the stored seed.
