Long-Term Effects of RF Dielectric Heating on Germination of Alfalfa Seed

ABSTRACT RADIOFREQENCY (RF) dielectric heating of alfalfa (Medicago sativa L.) seed that contained high percentages of hard seeds, i.e., seeds with moisture-impermeable seedcoats, rendered many of the hard seeds permeable and substantially increased the normal-seedling germination. Alfalfa seed samples treated at frequencies of 39 Mhz and 2.45 GHz responded similarly, and different electric field intensities used at those frequencies also produced similar responses as long as temperatures produced in the seed samples by the RF treatments were comparable. During storage periods of 10 to 21 yr at 4 °C and 40 to 50% rh, hard-seed percentages declined naturally in all seed lots tested. However, at the end of the storage period, treated samples of some seed lots still had significantly lower hard-seed percentages and significantly greater normal-seedling germination counts than did the untreated controls. Alfalfa seed samples treated with proper RF dielectric heating exposures suffered no detrimental effects that were detectable in germination tests during storage for periods up to 21 yr after treatment.