ABSTRACT
This chapter explores cell suspension cultures from the freezing-tolerant cultivar Anik as a model to study signal transduction and gene expression during cold acclimation. The abscisic acid (ABA) content of plant tissues increases during cold acclimation, and an exogenous application of ABA to seedlings maintained at 25°C results in an increased tolerance to subsequent freezing temperatures. The results of experiments on alfalfa cell suspension cultures also show that ABA increases cellular tolerance to freezing temperatures. The cold acclimation-induced accumulation of transcripts occurs in all parts of the seedling. The chapter explores the relationship between the level of cas gene expression and the degree of freezing tolerance of various alfalfa cultivars. Freezing tolerance can be induced in alfalfa seedlings and cell suspension cultures by cold acclimation or by exogenous application of ABA. The level of freezing tolerance induced by ABA is considerably lower than that induced by cold acclimation.
