Different concentrations of abscisic acid (ABA), naphthalene acetic acid (NAA) and methyl jasmonate (MeJa) were applied to maize (Zea mays) plants exposed to cold stress. ABA enhanced plant resistance against the damaging effects of freezing. ABA-treated plants produced some specific proteins when exposed to cold. Prominent changes were observed in the size and number of stomata with the application of ABA during cold stress. MeJa inhibited root growth, but increased root dry weight during cold acclimation. The chlorophyll content was lower at 100 mu g ml(-1) NAA and 50 mu g ml(-1) MeJa and higher in the residual applications when compared with that in the control plants. Carotenoid levels increased in all NAA and some ABA treatments, decreased however in MeJa treatment. Exogenous MeJa treatments increased endogenous trans-zeatin (t-Z) and indole-3-acetic acide (IAA) in contrast decreased ABA levels. Exogenous NAA also increased endogenous IAA, ABA and zeatin riboside (ZR) levels, while exogenous ABA decreased endogenous IAA and ZR levels.