The salicylic acid analog 2,6-dichloroisonicotinic acid has specific impact on the response of the halophyte plant species Solanum chilense to salinity

Salicylic acid (SA) is involved in the salt-resistance of the halophyte plant species Solanum chilense. The SA analog 2,6-dichloroisonicotinc acid (INA) is commonly used to elicit SA signal transduction in response to biotic stress and is frequently used to confirm the SA involvement in plant response to pathogens. Data are lacking concerning its impact on plant response to salinity, especially in the halophyte species. Solanum chilense was cultivated in the absence or presence of 125 mM NaCl in nutrient solution and exposed to 0.01 mM exogenous SA or sprayed with 0.5 mM INA. Exogenous SA increased the shoot dry weight while INA did not. Exogenous INA, in contrast to SA, increased the shoot Na+ concentration in NaCl-treated plants and decreased the root K+ concentration. In the absence of salt, both SA and INA induced an increase in H2O2 which was not due to ascorbate peroxidase (EC 1.11.1.11) inhibition. In salt-treated plants, SA stimulated the ascorbate peroxidase activity while INA did not. Exogenous SA increased the root putrescine and spermidine concentrations while INA significantly decreased the concentration of these protecting compounds. It is concluded that exogenous SA and INA do not have similar impacts on the plant behavior and that the difference between these compounds may be influenced by NaCl. The use of INA as a reliable SA analog should therefore be considered with caution in halophyte plant species.