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Subject: Plant Physiology × Author: Jangra, Manish × End date: 2018 × Start date: 2016 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Mitigating the effect of salt stress by foliar application of salicylic acid in sorghum (Sorghum bicolor L.) genotypes
    (CCSHAU, 2018) Jangra, Manish; Sarita Devi
    The present study entitled “Mitigating the effect of salt stress by foliar application of salicylic acid in sorghum (Sorghum bicolor L.) genotypes” was investigated in the screen house during the kharif season of 2017. Before sowing, the desired levels of salt stress (control, 5, 7.5 and 10 dS m-1) were maintained by saturating each pot. Salicylic acid (25 and 50 mg l-1) was applied exogenously after 30 and 70 days after sowing (DAS) under stressed as well as non-stressed plants in both genotypes (HJ 513 and HJ 541). Sampling was done at 40 and 80 DAS. Seeds of Sorghum bicolor L. were grown in pots under screen house conditions on 19th July 2017. Growth parameters decreased with increasing levels of salt stress, whereas foliar application of salicylic acid enhanced the growth of plants at both stages. Similarly, plant water relation, gaseous exchange studies, total chlorophyll, chlorophyll content (SPAD units) and photochemical quantum yield also showed declining trend from control to 10 dS m-1 of salt level in both genotypes, but per cent decrease was observed at 10 dS m-1 of salt stress like in ψw (43.0%), ψs (75.0%), photosynthetic rate (58.7%), transpiration rate (49.2%) and stomatal conductance (75.0%) in HJ 513 at 40 DAS, over their respective control. The values ranged from 3.18 to 2.10, 44.59 to 25.93 and 0.752 to 0.681 in total chlorophyll, chlorophyll content (SPAD units) and photochemical quantum yield (Fv/Fm) respectively, decreased at 10 dS m-1 of salt stress in HJ 513 at 40 DAS. Application of SA help in the amelioration of plant water status, exchange of gases and chlorophyll pigment irrespective of salt stress in both genotypes at 40 and 80 DAS. Reversibily, electrolyte leakage, MDA content and H2O2 content enhanced with every increment of salt stress but application of SA ameliorate the adverse effect of salt stress to some extent at both stages. Specific activity of antioxidative enzymes and osmolytes enhanced abruptly under salt stress in both genotypes and application of salicylic acid further enhanced these values at both 40 and 80 DAS. Per cent increase was on higher side at 10 dS m-1 of salt level in HJ 513 at 40 DAS viz. SOD (12.8%), CAT (11.3%), POX (9.9%), proline (15.1%), TSC (27.7%) and glycine betaine (22.3%) over their respective control. Higher Na+/K+ ratio was observed under salt stress but Na+/K+ ratio was maintained lower upon application of SA. Seed yield reduced significantly by decreasing yield attributing characters i.e. panicle length, panicle weight, seed yield per plant, 100 seed weight and harvest index under salt stress. Reduction in seed yield was ranged from 13.2 to 9.7 in HJ 513 and 11.9 to 8.7 in HJ 541 at 10 dS m-1. Conclusively, based on the above studies it can be concluded that after foliar spray of SA, HJ 513 performed better under salt stress by maintaining higher plant water status, photosynthetic rate, antioxidant defence system, seed yield and lower values of MDA content, electrolyte leakage and H2O2 content. SA treatments not only mitigate the inhibitore effect of salt stress on plants, but also showed, a stimulating effect and 50 mg l-1 of SA was found more effective than 25 mg l-1 at both sampling stages i.e. 40 and 80 DAS.