Exogenous salicylic acid increases polyamine content but may decrease drought tolerance in maize

It was shown in a previous work that 0.5 mM salicylic acid (SA) added in the hydroponic solution of maize increased its tolerance to low temperature stress [Planta 208 (1999) 175]. The effect of SA and cold treatments on polyamine content in the leaves was investigated using the HPLC technique in this work. Both 0.5 mM SA and cold treatment caused a significant increase in putrescine content. Spermidine increased only when the addition of SA was followed by low temperature stress. The spermine content decreased after both SA and low temperature treatments. The parallel use of 0.5 mM SA and 15% PEG caused a dramatic increase in the electrolyte leakage and a decrease in certain photosynthetic parameters in maize and wheat. It is concluded that the 0.5 mM SA pre-treatment, which increased the chilling tolerance, caused an increased sensitivity to drought. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.