Screening of plant resources with anti-ice nucleation activity for frost damage prevention

<p>Previous studies have shown that some polyphenols have anti-ice nucleation activity (anti-INA) against ice-nucleating bacteria that contribute to frost damage. In the present study, leaf disk freezing assay, a test of <i>in vitro</i> application to plant leaves, was performed for the screening of anti-INA, which inhibits the ice nucleation activity of an ice-nucleating bacterium <i>Erwinia ananas</i> in water droplets on the leaf surfaces. The application of polyphenols with anti-INA, kaempferol 7-<i>O</i>-β-glucoside and (–)-epigallocatechin gallate, to the leaf disk freezing assay by cooling at −4–−6 °C for 3 h, revealed that both the compounds showed anti-INAs against <i>E. ananas</i> in water droplets on the leaf surfaces. Further, this assay also revealed that the extracts of five plant leaves showed high anti-INA against <i>E. ananas</i> in water droplets on leaf surfaces, indicating that they are the candidate resources to protect crops from frost damage.</p> <p>Water droplets with ice-nucleating bacteria on leaf disks were hardly frozen by addition of leaf crude extracts. Unfrozen leaf disks survived freezing injury.</p

Anti-Ice Nucleating Activity of Surfactants against Silver Iodide in Water-in-Oil Emulsions

Various water-soluble substances are known as anti-ice nucleating agents (anti-INAs), which inhibit heterogeneous ice nucleation initiated by ice nucleating agents (INAs). Among them, several surfactants are reportedly effective as anti-INAs especially against silver iodide (AgI), which is a typical inorganic INA that induces heterogeneous ice nucleation at relatively high temperatures. In this study, the anti-ice nucleating activities of seven surfactants were examined in emulsified surfactant solutions containing AgI particles. Among previously reported anti-INAs (e.g., antifreeze proteins (AFPs), polyphenol compounds and synthetic polymers), a cationic surfactant used in this study, hexadecyltrimethylammonium bromide (C16TAB), showed the highest anti-ice nucleating activity against AgI. Based on the unique concentration-dependent dispersibility of AgI particles in C16TAB solution, the anti-ice nucleating activity of C16TAB must be caused by the adsorption of C16TAB molecules on AgI surfaces either as a monolayer or a bilayer depending on the C16TAB concentration