Supercooling capacity of seeds and seedlings in Arabidopsis thaliana

The influence of the water content of seeds and seedlings of Arabidopsis thaliana (Ecotype Columbia:2) on their supercooling capacity was investigated. Equilibration of the seeds to various air relative humidities resulted in final moisture contents ranging from 8 to 82% (dry weight basis). No supercooling point could be detected when the water content remained below 32.5%, and in seeds at just above this moisture level ice crystals started to form at -26 degrees C. However, cooling partly affected the germination of seeds down to a water content of 26.5%. Upon imbibition, the supercooling point of the seeds remained around -21.6 degrees C and rose sharply to -14.7 degrees C when visible germination started. It remained around -13 degrees C during the following 96 h while the water content of the seedlings increased from 155 to 870%. Hydrated seeds (above 32.5% water content), germinated seeds, and seedlings of Arabidopsis cannot survive being frozen. (C) 1999 Academic Press.