Abstract
Xylem parenchyma cells of boreal hardwood species adapt to subfreezing temperatures by deep supercooling, keeping protoplast water to liquid state near -40C. Our recent study indicated that any unknown intracellular substances concerned to promote supercooling in xylem parenchyma cells. Thus, we searched such substances that may promote supercooling in xylem parenchyma cells from soluble extracts of xylem tissues in Cercidiphyllum japonicum. We could isolate four anti-ice nucleation substances from the soluble extracts. UV, MS and NMR spectrums revealed that these substances were all flavonol monoglucosides. Among them, kaempferol-7-O-β-glucoside showed the highest supercooling capability of -9.0C at 1.0 mg/mL. Now, we are investigating the intracellular localization of these flavonols and seasonal fluctuation of the contents in xylem tissue, in order to clarify the role of these flavonols to deep supercooling capability of xylem parenchyma cells.
