Variability in evaluating ultra high dilution effects: considerations based on plant model experiments

A series of experiments, performed on plant models with ultra high dilutions (UHD) of arsenic trioxide at 45th decimal potency has been reviewed with a particular focus on variability. The working variables considered are: the number of germinated seeds out of a fixed set of 33, the stem length of wheat seedlings and the number of necrotic lesions in tobacco leaf disks inoculated with tobacco mosaic virus (TMV). A thorough comparison between treatment and control group has been proposed, considering the two main sources of variability in each series of experiments: variability within- and between- experiments. In treated groups, a systematic decrease in variability between-experiments, as well as a general decrease, with very few exceptions, in variability within-experiments, have been observed with respect to control. Variability is traditionally considered as control parameter of model systems. Our hypothesis, based on experimental evidences, proposes a new role for variability as a target of UHD action. This hypothesis may help interpret unanswered questions that keep rising in basic and clinical research in homeopathy.