Response of Okra [Abelmoschus Esculentus 9L.) Moench] to Exogenous Application of Alpha Tocophero as Foliar Application and Pre Seed Treatment Under Saline Conditions

Abstract

Okra (Abelmoschus esculentus) is Mallow vegetable growing in tropical areas of the world. Like all other agricultural crops, vegetables are also prone to several abiotic stresses throughout the world. Salinity is also one of these stresses that can cause reduction in per ha productivity of vegetables. Alpha tocopherol (vitamin E) as lipophilic antioxidant shields the plants from salinity induced damages by scavenging reactive oxygen species (ROS) in abiotic stresses including salinity. Two separate experiments were carried-out twice at Old Botanical Garden, UAF to observe the effect of α-tocopherol as priming agent and foliar spray on morpho-physiological responses of okra varieties (Noori and Sabzpari) to salinity stress. Plants were raised in sand filled plastic pots in full strength Hoagland’s nutrient solution. Four α-tocopherol levels (0, 100, 200 and 300 mg L-1) and two salt levels (0 and 100 mM) were maintained during current investigation. Salinity severely affected growth and yield of okra by decreasing fresh and dry weights of root and shoot and their lengths, photosynthetic pigments, gas exchange attributes, Ca2+ and K+ uptake. However, foliar spray and seed treatment of α-tocopherol markedly enhanced growth and yield of tested okra varieties by improving shoot and root length, shoot and root fresh and dry weights, photosynthetic pigments, photosynthesis and transpiration, WUE, stomatal conductance, activities of antioxidants (CAT, GPX, POD, SOD, protease, ascorbic acid and total phenolics) and fruit GB and total free proline contents under saline and salinity free conditions. Moreover, α-tocopherol application as pre-sowing seed treatment significantly ameliorated salinity induced damages in okra by reducing MDA, H2O2 in leaves and Na+ ion concentration in shoots, roots and fruits tissues, and by increasing K+ and Ca2+ uptake in shoots, roots and fruit tissues of both okra varieties under control and saline conditions. Of both okra varieties, Noori performed better than Sabzpari in all parameters. Inclusively, 200 and 300 mg L-1 of alpha tocopherol were more effective in improving growth and yield by demising brutal effects of salt stress at morpho-physiological levels and externally applied α-tocopherol as foliar spray treatment was more effective than priming in mitigating salinity stress.