24-Epibrassinolide ameliorates the saline stress and improves the productivity of wheat (Triticum aestivum L.)

Two wheat (Triticum aestivum L.) cultivars, Sids 1 and Giza 168, were grown under non-saline or saline conditions (4.7 and 9.4 dS m^?1) and were sprayed with 0.00, 0.05 and 0.10 mg l^?1 24-epibrassinolide (EBL). Salt stress considerably decreased plant productivity, membrane stability index, photochemical reactions of photosynthesis, the content of relative water, chlorophyll and nitrate, the activity of nitrate reductase and carbonic anhydrase and the level of carbohydrate and protein. The reduction was more pronounced in Giza 168. The follow-up treatment with 0.1 mg l^?1 EBL detoxified the stress generated by salinity and significantly improved the above parameters, especially in Sids 1. Glycinebetaine concentration was sharply elevated by salt stress and/or EBL treatments, particularly in Sids 1. Salinity increased putrescine level in Sids 1 and Giza 168, however, spermidine and spermine increased in Sids 1 and decreased in Giza 168. Exogenously applied EBL had a varying effect on polyamines pool under saline condition, an increase in putrescine level associated with low contents of spermidine and spermine in Giza 168 was observed, while Sids 1 showed a decrease in putrescine and high increase in spermidine and spermine. EBL prevented diamine oxidase and polyamine oxidase inhibition, indicating a positive correlation between salt tolerance and polyamines accumulation. Obviously, EBL can be a practical strategy toward generating high-yielding plants under saline condition by enhancing carbon and nitrogen metabolisms. This is the first report dealing with EBL effect on polyamines pool under salt stress.