Abscisic Acid-induced freezing resistance in cultured plant cells.

The effect of abscisic acid (ABA) on the cold hardiness of cell suspension was investigated. Cell suspension cultures of winter wheat (Triticum aestivum L. cv Norstar), winter rye (Secale cereale L. cv Cougar), and bromegrass Bromo inermis Leyss treated with 7.5 x 10(-5) molar ABA for 4 days at 20 degrees C could tolerate -30 degrees C, whereas the control cultures tolerated only -7 to -8 degrees C. The optimum concentration for increasing the cold hardiness of the cultures was 7.5 x 10(-5) molar. The degree of cold hardiness and the rate of hardening obtained by ABA treatment was significantly higher than that induced by low temperature alone. Of ten species tested, ABA was only effective on those cultures which were capable of cold hardening upon exposure to low temperatures. The results suggest that ABA bypasses the cold requirement for hardening and also suggests that ABA triggers the genetic system(s) responsible for inducing the hardening process.