Effect of ABA on freezing resistance of Betula papyrifera and Alnus incana woody plant cell suspensions.

Treatment of birch (Betula papyrifera Marsh) and alder (Alnus incana (L.) Moench) cell suspension cultures with ABA increased the freezing resistance of the cells. After 7 days of treatment with 10(-5) M ABA, birch cells grown at 23 and 4 degrees C attained an LT(50) of -16.9 and -14.1 degrees C, respectively, whereas control cells had an LT(50) of -9.1 degrees C. In alder cell suspensions, treatment with 10(-5) M ABA at 23 degrees C induced a small increase in freezing resistance from -7.3 to -10.8 degrees C. Exposure to 4 degrees C alone did not induce a significant increase in hardiness in birch cell suspensions. Addition of 10(-5) M ABA to the medium inhibited fresh weight increase over 10 days of 3-g inocula of birch and alder by 70 and 52%, respectively. With the same concentration of ABA in the medium we found different intracellular ABA concentrations in 3- and 6-g inocula. We conclude that the concentration of ABA in the medium does not reflect the intracellular concentration of tissue cultures, and that cultural conditions may influence ABA accumulation by cell cultures.