In this protocol, plant
freezing was initiated by inoculation from ice in the soil and spread
first to the lower stem and then through the rest of the plant. (2)
Plants were cut at the base, the cut stems were sealed with vac-
uum grease to prevent leakage of xylem fluids, the surface of the
plants were sprayed with an ice nucleating active strain (Cit7) of
Pseudomonas syringae bacteria, and cooled at a rate of 5 ◦ C h−1 .