Plants cannot escape adverse environmental conditions. Abiotic stresses associated with water (such as drought, continual rain and temperature extremes) reduce plant growth and thereby decrease yield and grain quality. Such stresses negatively affect natural distribution ranges and cultivation areas. Plant stress responses have been characterized using physiological and biochemical approaches, but few studies have applied biophysical approaches to investigate plant water relations. First, this review introduces the use of differential thermal analysis of tissue water to examine freezing tolerance in woody plants, especially various Rhododendron species that have different ecological habitats. The supercooling ability of flower buds appears to be sufficient to avoid freezing stress at the northern limit of natural distribution of each species. Second, the dynamic states of water determined from 1H-NMR relaxation times (T1, T2) in various plant organs such as flower buds, petals, seeds, hypocotyls, leaves and roots closely reflect senescence, maturation and stress injury. Therefore, analysis of water status in plant organs provides a sensitive and non-invasive way for evaluating both primary and lethal responses to stresses at various growth stages. Plants protect cell metabolism in response not only to drought as abiotic stress but also to seed desiccation. The production of highly vigorous seeds is important to a stable yield. Intracellular ‘glass transition’ is indispensable for the long-term seed survival in a dry state. The change in water compartments and the loss of water mobility in ripening seeds reflect cellular heterogeneity with accumulation of nutrients such as carbohydrates, lipids and proteins. This article also describes serious agricultural problems that result in yield losses and low grain quality in crops exposed to environmental stresses, with a particular focus on the remobilization of nutrients and dynamic states of water during seed filling. Because water is an essential factor that facilitates seed development and maturation, seeds must have mechanisms that allow them to withstand water loss.

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Muscle softening or mushiness of shrimp occurs generally during storage and distribution in ice. This phenomenon is caused by the muscle protein degradation due to the proteolytic activity. The purpose of this study was to understand quality improvement for P. vannamei by soybean powder. Soybean powder improved texture and yield of heat-treated P. vannamei. Based on inhibitor study, SBTI (soybean trypsin inhibitor) showed the highest inhibition at pH7.0 and pH9.0, while Pepstatin A exhibited the higher inhibition at pH3.0. Autolysis in P. vannamei meat could be inhibited mainly by SBTI and partially by a cysteine protease inhibitor, and EDTA at neutral and alkaline pH values.

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X-ray reflectivity analysis is an effective method to investigate the unusual behavior of ultrathin sugar films, in particular, the temperature dependence of their physical parameters. In this study, the change in thickness of ultrathin trimethyl β-cyclodextrin (TMβCD) films due to variation in temperature was verified under anhydrous condition for films with thickness less than 25 nm. As a result, the irreversible change in film-thickness during cooling and heating was confirmed by measurements. The irreversible change appeared above the glass transition temperature (Tg). Above this temperature, in addition to thickness change in the perpendicular direction, an irreversible linear expansion of the film occurred in the parallel direction. It is assumed that this behavior is due to the lack of strong interactions between the TMβCD molecules in ultrathin films and/or between the TMβCD molecule and Si substrate.

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The post-thaw cell survival rate as a function of cooling rate commonly has a bell shape with an optimal cooling rate. This characteristic is understood on the basis of two-factor hypothesis, i.e. cell injuries due to extracellular- and intracellular ice formations (EIF and IIF). The IIF-induced injury was already modeled successfully based on intracellular ice nucleation theory. In this study, first the experiment was performed to investigate the post-thaw cell viability and influence of cell freezing-patterns (EIF and IIF) to the cell viability. Next, the mathematical model with reaction kinetic formulation, developed previously by the authors, was applied to the experiment to describe the EIF-induced injury. An inverse problem analysis based on the experiment was performed to compare the cell survival rate as a function of cooling rate between the experiment and prediction by the model. The result shows that the EIF-induced cell injury is successfully described by the reaction kinetic model.

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Many plants in temperate regions enhance their freezing tolerance in winter. This phenomenon is known as cold acclimation (CA). CA is controlled not only by low temperature but also by photoperiod via phytochrome, a red/far-red photoreceptor. In Arabidopsis thaliana, phytochrome B (PHYB) is a key factor to integrate photoperiod information into CA process. In the field, the daily temperature fluctuation is entrained by a 24-h light-dark cycle. However, previous studies have not been focused on it. Here, we studied the effect of photoperiod and daily temperature fluctuation on CA, focusing on the role of PHYB. Arabidopsis wild type (WT) and phyB mutant were cold-acclimated for 7 days under 8-h or 12-h photoperiod, and then freezing tests were performed. On CA at constant 2°C, the freezing tolerance of phyB was significantly lower than that of WT only under 12-h photoperiod. On CA at 11°C light/2°C dark, the freezing tolerance of phyB was significantly lower only under 8-h photoperiod. Our results suggest that the CA regulation mechanism via PHYB differs with the temperature condition on CA.

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Global warming has encouraged farmers to start planting earlier. However, these advanced plantings also increase the risk by low-temperature stress. Therefore, accelerated germination under low-temperature conditions and enhanced chilling stress tolerance of seedlings are important factors to increase crop production. Here we show that a single seed treatment using a mixture of hydrogen peroxide (H2O2) and a trace amount of transitional metal catalyst can accelerate germination under cool temperature conditions. When seeds were germinated at 23ºC or 11ºC in the dark, the treated seeds germinated earlier than the control seeds. Furthermore, the treatment was effective long after germination: seedlings from the treated seeds showed faster root growth at both 23ºC and 11ºC. This treatment could provide a sustainable method to improve growth performance under both optimum and chilling conditions.

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