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Changes in the bioelectric activity of maize leaves caused by a single light pulse (6 s; 70 mol m-2 s-1) were used to compare the effects of NaCl treatment (20–200 mM) on plant growth, Na+ accumulation in leaves, chlorophyll fluorescence and pigment composition. Bioelectric responses seemed to be the most sensitive indicator of NaCl effects. Even the weakest salt treatment (20 mM) caused a statistically significant decrease (about 40%) in the amplitude of the bioelectric response. The higher the NaCl concentration, the smaller was the amplitude. Over the full concentration range, the characteristic time of response increased from about 30 to 60 sec, indicating that the rate of bioelectric changes was slowed by increasing salinity. Other reliable characteristics were found to be the fluorescence yield and quenching coefficients. The Fv/Fm ratio was not significantly affected by NaCl treatment. Changes in growth rate, biomass or pigment composition were either insensitive, or showed a plateau over a wide range of NaCl concentrations, and were inappropriate for screening. A possible link between bioelectric and fluorescence characteristics is discussed. We conclude that leaf bioelectric activity can be used together with, or instead of, chlorophyll fluorescence measurements, to screen genotypes for salt tolerance.

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Interest in the development and adoption of nonthermal technologies is burgeoning within the food and bioprocess industry, the associated research community, and among the consumers. This is evident from not only the success of some innovative nonthermal technologies at industrial scale, but also from the increasing number of publications dealing with these topics, a growing demand for foods processed by nonthermal technologies and use of natural ingredients. A notable feature of the nonthermal technologies such as cold plasma, electrohydrodynamic processing, pulsed electric fields, and ultrasound is the involvement of external fields, either electric or sound. Therefore, it merits to study the fundamentals of these technologies and the associated phenomenon with a unified approach. In this review, we revisit the fundamental physical and chemical phenomena governing the selected technologies, highlight similarities, and contrasts, describe few successful applications, and finally, identify the gaps in research.

Post-harvest needle abscission is a major challenge for Christmas tree and greenery industries. It was hypothesized that ethylene triggers abscission in balsam fir. Three experiments were conducted to test this hypothesis. In experiment 1, 70 balsam fir branches were collected, placed in water, and ethylene evolution was observed over time. In experiment 2, a 2 9 5 factorial experiment was designed to determine the effect of exogenous ethylene and an ethylene receptor blocker, 1-methylcyclopropene (1-MCP), on needle abscission. In experiment 3, a 2 9 6 factorial experiment was designed to determine the effect of exogenous ethylene and an ethylene inhibitor, aminoethoxyvinylglycine (AVG), on needle abscission. It was found that ethylene evolution was the highest 1-2 days prior to needle abscission, which was consistent in untreated branches and branches exposed to exogenous ethylene. Exposure to exogenous ethylene significantly decreased needle retention by 63%. When ethylene receptors were blocked by 1-MCP, needle retention increased by 147% despite the presence of ethylene and increased by 73% in the absence of ethylene when compared to the respective controls. When endogenous ethylene synthesis was inhibited by AVG, there was no improvement in needle retention in the presence of ethylene, but there was a 113% increase in needle retention in the absence of exogenous ethylene. Ethylene is strongly implicated as the signal triggering abscission in rootdetached balsam fir.

Previous experiments have demonstrated positive effect of Acadian® extract of Ascophyllum nodosum on plant stress-resistance, however the mode of action is not fully understood. The aim of this study was to understand the physiological effect of Acadian® seaweed extract on the plant response to drought stress. Leaf temperature and leaf angle were measured as early-stage indicators of plant stress with thermal imaging “in situ” over a 5-day stress-recovery trial. The early stress-response of control became visible on the third day as a rapid wilting of leaves, accompanied with the asymptotic increase of leaf temperature on 4–5 °C to the thermal equilibrium with ambient air temperature. At the same time Acadian® treated plants still maintained turgor, accompanied with the linear increase in leaf temperature, which indicated better control of stomatal closure. Re-watering on the fifth day showed better survival of treated plants compared to control. This study demonstrated the ability of Acadian® seaweed extract to improve resistance of soybean plants to water stress.

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