Effects of 24-epibrassinolide on plant growth, osmotic regulation and ion homeostasis of salt-stressed canola

This study evaluated effects of foliar spraying 24-epibrassinoide (24-EBL) on the growth of salt-stressed canola. Seedlings at the four-leaf stage were treated with 150mm NaCl and different concentrations of 24-EBL (10(-6), 10(-8), 10(-10), 10(-12)m) for 15days. A concentration of 10(-10)m 24-EBL was chosen as optimal and used in a subsequent experiment on plant biomass and leaf water potential parameters. The results showed that 24-EBL mainly promoted shoot growth of salt-stressed plants and also ameliorated leaf water status. Foliar spraying of salt-stressed canola with 24-EBL increased osmotic adjustment ability in all organs, especially in younger leaves and roots. This was mainly due to an increase of free amino acid content in upper leaves, soluble sugars in middle leaves, organic acids and proline in lower leaves, all of these compounds in roots, as well as essential inorganic ions. Na+ and Cl- sharply increased in different organs under salt stress, and 24-EBL reduced their accumulation. 24-EBL improved the uptake of K+, Ca2+, Mg2+ and NO3- in roots, which were mainly transported to upper leaves, while NO3- was mainly transported to middle leaves. Thus, 24-EBL improvements in ion homeostasis of K+/Na+, Ca2+/Na+, Mg2+/Na+ and NO3-/Cl-, especially in younger leaves and roots, could be explained. As most important parts, younger leaves and roots were the main organs protected by 24-EBL via improvement in osmotic adjustment ability and ion homeostasis. Further, physiological status of growth of salt-stressed canola was ameliorated after 24-EBL treatment.