Madaan, ShashiMidathala, Raghavendra2017-10-032017-10-032017http://krishikosh.egranth.ac.in/handle/1/5810032094The present investigation was aimed to study the effect of spermine and salt stress on two tolerant (Kharchia 65 and KRL 210) and two susceptible wheat varieties (DBW 88, HD 3086). Salt stress was imposed before sowing by irrigating the pots with artificial saline water of 8 and 12 dSm-1. Spermine of 0.5 and 1.0 mM were sprayed over the plants at 21 and 90 days after sowing. The leaf samples were analysed for various physiological and biochemical parameters at 0, 5, 10 and 15 days after spermine treatment. The physiological parameters like RWC, osmotic potential, chlorophyll fluorescence and leaf membrane injury declined with increasing salinity levels and decrease was more in susceptible varieties than tolerant varieties. Compared to susceptible varieties, Kharchia 65 and KRL 210 had lower levels of H2O2, O2˙ˉ and MDA which can be ascribed to an elevated levels of antioxidant metabolites like glutathione, carotenoids and effective ROS scavenging enzymes such as SOD, APX, GR, Gpx. The exogenous spermine improved the plant water status, activities of the antioxidant enzymes, metabolites and was effective in triggering the protection against salt-induced cellular damages by scavenging H2O2, O2˙ˉ and MDA content. In addition, accumulation of elevated levels of proline in tolerant varieties may be due to the increased activity of proline biosynthesizing enzymes (P5CS, P5CR) and repressed proline oxidase enzyme. The exogenous spermine may be associated with the capacity to maintain high levels of Spm, Spd and lower level of Put which in turn may be due to stimulated DAO activity and suppressed PAO activity thus accumulating higher PAs like Spm & Spd under salt stress. Isoenzymic pattern revealed single form for DAO whereas two forms of PAO were visualized on native PAGE gels under salt stress and spermine treatment. Further, application of spermine improved grain quality, yield and prolong grain filling duration under salinity. The results demonstrated that exogenous application of 0.5mM spermine could partially alleviate the deleterious effects of salinity.ennullThesis