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 wi th 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 cu lture medium resulted in maximum chilling tolerance (40%). The results of a cell regrowth assay were consistent with viability determined by the TTC m ethod. In suspension-cultured cells supplemented with various concentration s of GB, accumulation of GB in the cells was proportional to the GB concent ration in the medium and was saturated at a concentration of 240 mu mol (g DW)(-1). The degree of increased chilling tolerance was positively correlat ed with the level of GB accumulated in the cells. The increased chilling to lerance 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 preve ntion of chlorosis after chilling for 3 d at 4 degrees C/2 degrees C. Lipid peroxidation, as expressed by the production of malondialdehyde, was signi ficantly reduced in GB-treated cells compared with the untreated controls d uring chilling. These results suggest that increased chilling tolerance may be due, in part, to the reduction of lipid peroxidation of the cell membra nes in the presence of GB.