Mitigating Salt Stress in Mustard (Brassica Juncea L.) through Foliar Application of Ascorbic Acid: Morphological, Physiological, and Biochemical Responses

Abstract

Mustard (Brassica juncea L.) is a member of the Brassicaceae family has great economic and medicinal importance. It is third important crop in world while in Pakistan it is second after the soya bean production. Excess amount of salt changes the soil composition and also effects soil microbial activity and plants roots are damage thus productivity of crop reduced. Ascorbic acid increases growth and productivity of mustard under the saline and normal conditions. The Experiment was conduct to check the use of ascorbic acid to alter negative effects of saltiness on mustard using two cultivar of mustard super Raya and Faisalabad mustard. The salt concentrations used were 0 mM and 100 mM of sodium chloride, applied by dissolving it in Hoagland’s solution after 10 days interval till vegetative stage. Ascorbic acid (AsA) was applied to the leaves at concentrations of 0 mM and 10 mM to counteract the harmful effects of salt stress. Statistical analysis showed that there was significant reduction in morphological parameters in both varieties under salt stress, while ascorbic acid treated plants exhibited an increase in morphological growth attributes. Saline conditions had significant decrease effects on chlorophyll a, chlorophyll b and carotenoids (40%, 34%, 37%) in V1 (47%, 40%, 39%) in V2 while ascorbic acid application increased (34%, 32%, 29%) in V1 (56%, 40%, 34%) in V2 the content in the current research. Substantial increases were recorded by enzymatic antioxidants (SOD, CAT and POD) in V1 and V2 and total soluble proteins, flavonoids, total soluble sugars content under salinity. There was significant increase in ROS production such as MDA and H2O2 under salt stress. While application of ascorbic acid showed remarkable decrease in MDA and H2O2 production. Salinity marked much increase in Na+ (40% and 40%) accumulation in leaf and root (52% and 55%)  by thereby reducing K+ and Ca2+ level ions under stress or increase under treatment of foliarly applied ascorbic acid. In contrast, ascorbic acid application enhanced these nutrient uptakes of ions to maintain the ion balance in mustard cultivar under saline stress.