Glycinebetaine increases chilling tolerance and reduces chilling-induced lipid peroxidation in Zea mays L.

Chilling tolerance was increased in suspension-cultured cells and seedlings of maize (Zea mays L. cv 'Black Mexican Sweet') grown in media containing glycinebetaine (GB). A triphenyl tetrazolium chloride (TTC) reduction test indicated that after a 7 d chilling period at 4 degrees C, cells treated with 1 mm GB at 26 degrees C for 1 d had a survival rate (30%) that was twice as high as that of untreated controls. The addition of 2.5 mM GB to the culture medium resulted in maximum chilling tolerance (40%). The results of a cell regrowth assay were consistent with viability determined by the TTC method. In suspension-cultured cells supplemented with various concentrations of GB, accumulation of GB in the cells was proportional to the GB concentration in the medium and was saturated at a concentration of 240 mu mol (g DW)(-1). The degree of increased chilling tolerance was positively correlated with the level of GB accumulated in the cells. The increased chilling tolerance was time-dependent; i.e. it was first observed 3 h after treatment and reached a plateau after 14 h. Feeding seedlings with 2.5 mM GB through the roots also improved their chilling tolerance, as evidenced by the prevention of chlorosis after chilling for 3 d at 4 degrees C/2 degrees C. Lipid peroxidation, as expressed by the production of malondialdehyde, was significantly reduced in GB-treated cells compared with the untreated controls during chilling. These results suggest that increased chilling tolerance may be due, in part, to the reduction of lipid peroxidation of the cell membranes in the presence of GB.