Exogenous spermidine, arsenic and beta-aminobutyric acid modulate tobacco resistance to tobacco mosaic virus, and affect local and systemic glucosylsalicylic acid levels and arginine decarboxylase gene expression in tobacco leaves.

The polyamine spermidine and the metalloid arsenic increased resistance responses in the well-known pathosystem NN tobacco/tobacco mosaic virus (TMV). Both the hypersensitive response to TMV in a leaf disk model system (inoculated disks floating in the 0.1mM treatments) and systemic acquired resistance (SAR) in whole plants were significantly affected. In the latter case, 1mM foliar sprays of spermidine and arsenic were as effective as TMV and dl-beta-aminobutyric acid (BABA), both taken as positive controls, in improving the plant's response to subsequent challenge inoculation with TMV. Moreover, this phenotypic response was correlated with changes in the endogenous concentration of the SAR-related molecule salicylic acid and in transcript levels of some pathogenesis/stress-related genes (pathogenesis-related proteins PR-1a and PR-2 and arginine decarboxylase (ADC)). Concentrations of free salicylic acid and of 2-O-beta-d-glucosylsalicylic acid and mRNA amount of PR-1a, PR-2 and ADC were analyzed in plants treated with either spermidine or arsenic, and compared with those from untreated plants and from positive (TMV-inoculated or BABA-treated) controls. Conjugated salicylic acid content and ADC transcripts were found to significantly increase, at both the local and systemic levels, relative to untreated controls.

The role of 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 has 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 of variability as a target of UHD action. This hypothesis may help interpret unanswered questions that keep rising in basic and clinical research in homeopathy.

Extremely low frequency weak magnetic fields enhance resistance of NN tobacco plants to tobacco mosaic virus and elicit stress-related biochemical activities.

Increasing evidence has accumulated concerning the biological effects of extremely low frequency magnetic fields (ELF-MFs) in different plant models. In the present study, effects of ELF-MFs in tobacco plants reacting to tobacco mosaic virus (TMV) with a hypersensitive response (HR) were evaluated. Plants were exposed for 8 or 24 h (either before or after TMV inoculation) to a static MF, at either -17 or 13 microT, combined with a 10 Hz sinusoidal MF with different intensities (25.6 or 28.9 microT). The working variables were the area and number of hypersensitive lesions in leaves. Following ELF-MFs exposure, an increased resistance was detected, particularly after an 8-h treatment, as shown by the decrease in lesion area and number. Moreover, two enzyme activities involved in resistance mechanisms were analyzed: ornithine decarboxylase (ODC) and phenylalanine ammonia-lyase (PAL). Uninoculated leaves previously exposed to ELF-MFs in general showed a significant increase relative to controls in ODC and PAL activities, in particular for 13 microT static MF plus 28.9 microT, 10 Hz sinusoidal MF (24 h) treatment. In conclusion, ELF-MFs seem to influence the HR of tobacco to TMV, as shown by the increased resistance and changes in ODC and PAL activities, indicating the reliability of the present plant model in the study of bioelectromagnetic interactions.

A biostatistical insight into the As(2)O(3) high dilution effects on the rate and variability of wheat seedling growth.

BACKGROUND: Most criticism of homeopathy concerns the lack of scientific bases and theoretical models. Fundamental research could make important contributions to our understanding of the mechanisms of action of homeopathic treatments. Plant-based bioassays are suitable for basic research -- lacking the placebo effect and ensuring large data samples for structured statistical analyses. OBJECTIVE: The aim of this study was to reproduce a previous experiment on the effects of arsenic trioxide (As(2)O(3)) high dilutions on wheat seedling growth in order to verify whether the same significant results could be obtained working in a different place and with a different experimental team. A further goal was to investigate high dilution effects on variability. MATERIAL AND METHODS: A structured experiment was performed blind over 9 weeks, using wheat seeds previously stressed with a sublethal dose of As(2)O(3). The seeds were then treated with either potentized As(2)O(3) (5x, 15x, 25x, 35x, 45x), potentized water (equivalent potencies) or diluted As(2)O(3) (10(-5), 10(-15), 10(-25), 10(-35), 10(-45)). The working variable was the stem length, measured after 4, 5, 6 and 7 days. RESULTS: Some potencies (As(2)O(3) 45x and H(2)O 45x) induced a relevant increase in seedling growth and/or a variability decrease. Diluted As(2)O(3) did not induce any significant results. CONCLUSIONS: Confirmation of a significant stimulating effect on seedling growth and a significant decrease of variability was obtained with ultra-high dilutions at the 45x potency. The model of wheat germination and growth has been confirmed to be a good tool for basic research in homeopathy.

Nonthermal microwave radiations affect the hypersensitive response of tobacco to tobacco mosaic virus.

OBJECTIVES: The aim of the present study was to evaluate the effects of nonthermal extremely high-frequency microwave radiations in a plant-based bioassay, represented by tobacco plants reacting to tobacco mosaic virus with a hypersensitive response leading to the appearance of necrotic lesions at the infection sites. DESIGN: This study was performed blind and different experimental protocols on tobacco plants inoculated with tobacco mosaic virus were used. BIO-OBJECTS: Tobacco plants (Nicotiana tabacum L. cultivar Samsun) carrying the resistance gene N against tobacco mosaic virus. INTERVENTIONS: Tobacco plants or leaf disks were either directly or indirectly (water-mediated) irradiated using a medical device, designed for microwave resonance therapy. It produces nonthermal weak-intensity extremely high-frequency radiations, either modulated at extremely low frequency or in continuous flux of waves, coupled with a nonthermal red/near-infrared radiation. OUTCOME MEASUREMENTS: The working variable was the number of hypersensitive lesions per leaf disk. RESULTS: Both direct and indirect nonthermal microwave radiations led to significant effects on the hypersensitive response of tobacco plants: modulated radiations generally induced a resistance increase, whereas a continuous flux of waves induced a resistance decrease with direct treatments only. CONCLUSIONS: Nonthermal microwave radiations are effective on the hypersensitive response of tobacco to tobacco mosaic virus and their low-frequency modulation seems to be more bioactive than the continuous-flux of waves, particularly in the indirect water-mediated treatments.