Seeds of tomato and oats were subject to hydration-dehydration treatments at various times during germination. Desiccation has little harmful effect if carried out before cell division and enlargement has commenced. Some advancement of the onset of germination was apparent due probably to slight changes in the seed covering and also to the initiation of metabolic events which could withstand the dehydration, e.g. the increased protease activity was maintained in the dried seed.
Dehydration can be done more than once. The effects are only truly accumulative if the prior imbibitions are of substantial duration.
Physical changes associated with hydration are fairly easily reversed but some of the chemical changes beginning in oat within 8–12 hours of imbibition cannot be returned to the original dry seed condition by desiccation. Once embryo growth is apparent, embryo damage of some sort usually results.