Effects of Exogenous Salicylic Acid on Drought Response and Characterization of Dehydrins in Impatiens walleriana

Impatiens walleriana is a valued ornamental plant sensitive to drought stress. We investigated whether the foliar application of 2mM salicylic acid (SA) can protect potted I. walleriana plants from drought stress. The plants were divided into: watered plants, drought-stressed plants, watered plants treated with SA and drought-stressed plants treated with SA. The number of flowers and flower buds, relative water content (RWC), contents of malondialdehyde (MDA) and proline (Pro) and the activities of superoxide dismutases, catalases and peroxidases were recorded at different time points. Three dehydrin sequences were identified in de novo assembled leaf transcriptome: IwDhn1, IwDhn2.1 and IwDhn2.2. Drought stress caused wilting, floral abortion, reduction of RWC and increased MDA—an indicator of lipid peroxidation. In response to drought, Impatiens accumulated Pro and induced chloroplastic Cu/ZnSOD and two peroxidase isoforms. The most remarkable drought response was strong induction of IwDhn2.1 and IwDhn2.2. Rehydration restored RWC, Pro level, Cu/ZnSOD activity and dehydrins expression in drought-stressed plants approximately to the values of watered plants.SA had ameliorating effects on plants exposed to drought, including prevention of wilting, preservation of RWC, increased Pro accumulation, modulation of antioxidative activities and remarkable decrease of lipid peroxidation, but without effects on flowers’ preservation.