Effects of homeopathic arsenic on tobacco plant resistance to tobacco mosaic virus. Theoretical suggestions about system variability, based on a large experimental data set.

CONTEXT This research aimed at verifying the efficacy of homeopathic treatments by plant-based bioassays, which may be suitable for basic research, because they lack placebo effects and provide large datasets for statistical analyses. OBJECTIVE To evaluate the effects of homeopathic treatments of arsenic trioxide (As2O3) on tobacco plants subjected to tobacco mosaic virus (TMV) inoculation as biotic stress. DESIGN Blind, randomized experiment using tobacco leaf disks. MATERIALS AND METHODS Tobacco plants (Nicotiana tabacum L. cultivar Samsun) carrying the TMV resistance gene N. TMV inoculated leaf disks were floated for 3 days in the following: Distilled water (control). H2O 5 and 45 decimal and centesimal potencies. As2O3 5 and 45 decimal and centesimal potencies. The main outcome measures is the number of hypersensitive lesions observed in a leaf disk. RESULTS Homeopathic treatments of arsenic induce two effects on the plant: (i) increased resistance to TMV; (ii) decrease variability between experiments (system variability). CONCLUSIONS In this experimental model two actions of homeopathic treatment were detected: decrease in system variability and enhancement of the natural tendency of the system towards an 'equilibrium point'.