Nitrogen Enhances Salt Tolerance by Modulating the Antioxidant Defense System and Osmoregulation Substance Content in Gossypium hirsutum

Abstract

Increasing soil salinity suppresses both productivity and fiber quality of cotton, thus, an appropriate management approach needs to be developed to lessen the detrimental effect of salinity stress. This study assessed two cotton genotypes with different salt sensitivities to investigate the possible role of nitrogen supplementation at the seedling stage. Salt stress induced by sodium chloride (NaCl, 200 mmol·L −1 ) decreased the growth traits and dry mass production of both genotypes. Nitrogen supplementation increased the plant water status, photosynthetic pigment synthesis, and gas exchange attributes. Addition of nitrogen to the saline media significantly decreased the generation of lethal oxidative stress biomarkers such as hydrogen peroxide, lipid peroxidation, and electrolyte leakage ratio. The activity of the antioxidant defense system was upregulated in both saline and non-saline growth media as a result of nitrogen application. Furthermore, nitrogen supplementation enhanced the accumulation of osmolytes, such as soluble sugars, soluble proteins, and free amino acids. This established the beneficial role of nitrogen by retaining additional osmolality to uphold the relative water content and protect the photosynthetic apparatus, particularly in the salt-sensitive genotype. In summary, nitrogen application may represent a potential strategy to overcome the salinity-mediated impairment of cotton to some extent.Plants 2020, 9, 450 2 of 20 most sensitivity to salinity during the seedling growth stage, and remained sensitive at the reproductive stage [9]. Excess salinity inhibits plant growth and development by inducing osmotic stress, particular ion toxicity (Na + and Cl − ), oxidative damage, and/or nutritional disorders in plant tissues, which subsequently lead to weakened plant growth and endurance [10][11][12]. Salt stress has been shown to significantly decrease the uptake and metabolism of numerous mineral nutrients (such as nitrogen, potassium, phosphorus, and calcium), and accelerate the damage of the photosynthetic machinery as well as the whole salt tolerance mechanisms of plants. Salt stress-induced plant metabolism alterations are the secondary consequence of carbon and nitrogen metabolism [13]. Moreover, a high salt concentration perturbs electron transport systems in both chloroplasts and mitochondria [14,15]. This accelerates electron leakage from electron transportation chains and induces the generation of reactive oxygen species (ROS), such as superoxide radicals, hydroxyl radicals, and hydrogen peroxide [16,17]. The over-accumulation of ROS not only damages cellular and biological activities [18][19][20], but also degrades chlorophyll pigments and obstructs the synthesis of proteins, amino acids, lipids, deoxyribonucleic acid, as well as enzymatic and non-enzymatic activities of plants [17]. To avoid ROS-induced oxidative damage, plant-assured endogenous tolerance approaches, such as the antioxidant defense system as well as the accumulation of organic solutes and secondary metabolites [21]....

Can Different Salt Formulations Revert the Depressing Effect of Salinity on Maize by Modulating Plant Biochemical Attributes and Activating Stress Regulators through Improved N Supply?

“…With optimum nitrogen nutrition, the adverse effects of salinity in maize plants were relegated, as evident by the decrease in the MDA concentration. In addition, the proline contents and antioxidant enzyme activities were regulated in order to limit the production of ROS, eventually invoking stronger N-mediated plant defense against salinity stress [64,65].…”

Evaluation of Cotton (Gossypium hirsutum L.) Leaf Abscission Sensitivity Triggered by Thidiazuron through Membership Function Value

“…Leaf relative water content (LRWC) [ 30 ] and natural water-saturated deficit (NWSD) were determined at 3 DAT as follows: Leaf fresh weight (FW) were weighted, then soaked in distilled water until saturated weight (SW), and, finally, dry weight (DW) was recorded. The calculation formula is as follows: …”

“…The contents of soluble sugar and amino acid in the fourth leaves were determined at 3 DAT Soluble sugar and amino acid was extracted by the ethanol-soluble extraction method, as described by Hu [ 31 ]. Soluble sugar and amino acid were determined by anthrone colorimetry [ 30 ] and ninhydrin solution detection [ 32 , 33 ], respectively.…”

Abscisic Acid and Nitrogen Showed Coordinated Action on Antioxidant System and Osmotic Adjustment to Alleviate Salinity Inhibited Photosynthetic Potential in <em>Brassica juncea</em> L.

“…It is obvious from the accessible literature that the exogenous supplementation of N or ABA alone enhances salinity tolerance in plants [33][34][35]. Nitrogen improves salinity tolerance by maintaining glutathione (GSH) production.…”