EXOGENOUS APPLICATION OF 24-EPIBRASSINOLIDE AND NANO-ZINC OXIDE AT FLOWERING IMPROVES OSMOTIC STRESS TOLERANCE IN HARVESTED TOMATO SEEDS

The favorable effects of exogenously applied brassinosteroids and zinc micronutrient on plant growth performance and seed development have been extensively outlined in many studies. Nevertheless, almost no published document is available on the effects of 24-epibrassinolide and nano-zinc oxide on tomato seed quality and osmotic stress tolerance of the resulted seedlings. In this study, the effects of 24-epibrassinolide (0, 15 and 30 mg.ha(-1) EBL) and nano-zinc oxide (0, 600 and 1200 ppm N-ZnO), which were exogenously applied on tomato mother plants, on seed germination parameters and stress tolerance capability of the produced seedlings under osmotic stress conditions (water potential of 0, -0.1 and -0.2 MPa stimulated by PEG-6000) were investigated. According to obtained results, the water potential of - 0.2 MPa resulted in the lowest seed germinability and seedling growth performance with the highest amount of proline, hydrogen peroxide, malondialdehyde and activity of catalase and peroxidase, compared to non-stress control. All the foliar treatments resulted in decreased H2O2 and MDA content, especially EBL2+N-ZnO2. In addition, foliar application of EBL and N-ZnO enhanced the activity of antioxidative enzymes and ameliorated the inhibitory effects of osmotic stress on tomato seedling growth, except for percentage and rate of germination.