Inductively Coupled Electrical Stimulation - Part 6: Duration of PEMF-induced enhanced seed germination
Authors: Dennis Robert 
Published: October 2023

The objective of this study was to directly answer the practical question: how long lasting are the observed effects of pulsed electro-magnetic fields (PEMF) on seed germination?  Earlier studies have shown that the effect of PEMF treatment on seed germination can be positive, neutral, or negative, exhibiting a tri-phasic inverse hormesis behavior as a function of total PEMF dosage during a single treatment session.  This allows an optimal dosage range to be determined for maximum progerminative effect.  Dosages in this range were found in earlier studies to increase the germination rate of pepper seeds to ~ 85%, from the baseline germination rate of ~56%, amounting to an increased germination rate of ~150% of baseline. 

One major practical consideration of this observation is whether the PEMF treatment is durable enough to allow central processing and long-term storage of the seeds for later use, or whether seeds treated by PEMF need to be planted shortly after treatment due to rapid loss of effect over time.  If the latter, what is the allowable time between PEMF treatment and planting?  In addition to their practical value, these observations will have considerable theoretical value as well.  As the underlying biophysical mechanism of PEMF remains to be elucidated, quantitative assessments of the durability of the effect of PEMF treatment will give important clues as to the potential mechanisms involved; for example, whether they involve the activation of enzyme systems that remain activated or taper off, whether they initiate the release or activation of substances in reserve in the germ that are exhausted upon a single use, whether multiple mechanisms are involved as evidenced by multi-phasic decay over time, or whether the progerminative effect can be repeated more than one time in any given seed.

For this study, the duration of the progerminative effect was measured by applying a previously-determined “optimal” dose of PEMF to pepper seeds, then storing the seeds in their original paper envelopes in a darkened room at 50% RH and room temperature for a period of up to one year post-treatment before planting, and determination of germination rate at two weeks (14 days).  Finally, we study whether the lost progerminative effect can be recovered in stored seeds by reapplication of PEMF at the same dose immediately before planting. 

Our findings were that (1) the progerminative effect lasted only about 2 days after PEMF exposure, then returned about half way back to baseline and began a slow decline thereafter, but remained at approximately half-way, never returning to baseline even for periods of storage as long as 1 year, (2) a second application of PEMF restored almost all of the progerminative effect even after storage periods of up to one year.  Storage periods longer than 1 year were not studied.

These results add to the discussion of the mechanisms of PEMF across the span of complex organisms by suggesting the involvement of multiple mechanisms, some durable while others are semi-permanent.