Seed biologists beware: Estimates of initial viability based on ungerminated seeds at the end of an experiment may be...

Seed viability is routinely measured on seeds that fail to germinate at the end of an experiment. Together with the number of germinants, this is used to estimate viability of the seeds at start of the experiment (i.e., initial viability) and provides the comparative basis on which germination success is determined. The literature and recent data on the germination requirements of Leucadendron species were examined to determine if there was any evidence for a treatment effect on viability of ungerminated seeds at the end of the experiment. The survey showed that sometimes (perhaps often, as the problem has yet to be recognized or reported) prolonged duration in the treatment, especially the control where little germination occurs, lead to loss of viability during the experiment. This resulted in underestimation of initial viability if that treatment was used. I caution against the routine use of end-of-trial germination and viability of ungerminated seeds as an estimate of initial viability in determining germination success of various treatments. I explore ways to deal with the problem but the preference is for estimates of initial viability to be undertaken on a separate sample of seeds concurrently with the experiment as this avoids the risk of seed death during the trial.