A brassinosteroid analogue prevented the effect of salt stress on ethylene synthesis and polyamines in lettuce plants

• Effects of BR analogue DI-31 on the lettuce plants under NaCl stress were assayed.
• DI-31 increased weight of lettuce seedlings under NaCl stress.
• DI-31 decreased respiration rate, ethylene production, and the content of ACC in lettuce plants under NaCl stress.
• DI-31 decreased the content of total polyamines in lettuce roots under NaCl stress.

The present study was carried out to analyze the effect of treatment with DI-31, a brassinosteroid analogue (0.1 or 1 μM), on alleviating salt stress in lettuce plants. After application of DI-31, 100 mM NaCl treatments were administered. Samples that were separated into shoots and roots were taken 5 days after this application. DI-31 alleviated the reduction of weight due to NaCl with a greater effect at 1 than at 0.1 μM. The emission of ethylene increased with the application of NaCl, and the DI-31 treatment decreased this effect in shoots and roots. Similar results were obtained in ACC, since its concentration was increased by salinity, and DI-31 was effective in reducing it. The putrescine content decreased with salinity and DI-31 reversed the effect in the shoots, while it remained constant in the roots. The spermidine and spermine contents in roots increased with salinity. The DI-31 reversed the effect of NaCl in both shoots and roots in the two polyamines, except in shoots where the spermine content was maintained. Since the DI-31 brassinosteroid has partially reversed the negative effect of NaCl on lettuce plants, we conclude that the brassinosteroid has a protective effect against salinity.