Exogenous salicylic acid positively affects morpho-physiological and molecular responses of Impatiens walleriana plants grown under drought stress

The aim of this experiment was to investigate the exogenous application of salicylic acid (SA) on morpho-physiological and molecular characteristics of Impatiens walleriana plants grown under water deficit stress. Three levels of soil water contents (95, 85, and 75% of field capacity; FC) and three levels of SA (0, 1, and 2 mM) were applied on two impatient cultivars (‘Tempo’ and ‘Salmon’). The results showed that increasing water deficit stress negatively affected growth and flowering characteristics. On the contrary, the foliar application of SA reduced the adverse effect of water deficit stress and improved growth and ornamental plant attributes. Water deficit increased the amount of electrolyte leakage (EL), malondialdehyde (MDA), peroxidase (POD) and ascorbate peroxidase (APX) activities; and proline content. The expression of the gene encoding for Δ1-pyrroline-5-carboxylate synthetase (P5CS) was slightly increased under control treatment (95% FC + SA 0 mM) and then significantly increased at 75% FC and after the SA treatments. The expression pattern of P5CR (Δ1-pyrroline-5-carboxylate reductase gene) was similar to that of P5CS, with differences in terms of intensity. The application of SA reduced the amount of EL and MDA through increased antioxidant activities and water balance. Overall, the results of this study showed that ‘Salmon’ cultivar was able to tolerate drought stress conditions better than ‘Tempo.’ The application of 2 mM SA increased growth and physiological indices in drought-stressed impatient, mitigating the detrimental effects of water deficit in this important ornamental species.