Characterization of Supercooling-Facilitating (Anti-Ice Nucleation) Hydrolyzable Gallotannins in Supercooling Xylem Parenchyma Cells in Katsura Tree (Cercidiphyllum japonicum)

Abstract

Xylem parenchyma cells (XPCs) of boreal trees adapt to subzero temperatures by deep supercooling. Previous studies suggested that intracellular substances were important for maintaining a supercooling state of cellular water at subzero temperatures in XPCs. In our recent studies, four kinds of flavonol glycosides and four kinds of hydrolyzable gallotannins were identified as supercooling-facilitating (SCF; anti-ice nucleation) substances in xylem extracts of katsura tree (Cercidiphyllum japonicum). In the present study, we examined SCF capabilities of the four kinds of hydrolyzable gallotannins in solutions containing different kinds of ice nucleators, including Erwinia ananas, Xanthomonas campestris, silver iodide, and 1,3,5-trihydroxybenzene (phloroglucinol). The results showed that all four gallotannins exhibited SCF capabilities in the solutions containing various kinds of ice nucleators, but capabilities were dependent on their concentrations and the type of ice nucleator used.