Low temperature acclimation to chilling tolerance in rice roots

Rice seedlings (Oryza sativa L.) were subjected to low temperature pretreatment (LT-PT; 10 degrees C) for various length of time (1, 2, 4, 6, 12, 18, 24 h) followed by a 48-h chilling temperature stress (2 degrees C). Chilling temperature tolerance of rice roots was improved with increasing duration of LT-PT, but LT-PT longer than 12 h gave no additional improvement. Alcohol dehydrogenase activity and ethanol concentration in the roots were increased with increasing duration of LT-PT up to 12 h. Chilling tolerance was also improved by exogenously applied ethanol. These results suggest that LT-PT may increase chilling tolerance in rice roots owing to ethanol accumulation in the roots and LT-PT acclimation to chilling temperature may occur within 12 h.