Lipoic Acid Combined with Melatonin Mitigates Oxidative Stress and Promotes Root Formation and Growth in Salt-Stressed Canola Seedlings (Brassica napus L.)

Abstract

Lipoic acid (LA) and melatonin (MT) are pleiotropic molecules participating in plant stress resistance by modulating cellular biochemical changes, ion homeostasis, and antioxidant enzyme activities. However, the combined role of these two molecules in counteracting the detrimental impacts of salinity stress is still unknown. In the present study, we determined the effects of exogenous LA (0.5 µM), MT (1 µM) and their combination (LA + MT) on growth performance and biomass accumulation, photosynthetic pigments, enzymatic and non-enzymatic antioxidant activities, and ions homeostatic in canola (Brassica napus L.) seedlings under salinity stress (0, 100 mM) for 40 days. The results indicate that exogenous application of LA + MT improved the phenotypic growth (by 25 to 45%), root thickness (by 68%), number of later lateral roots (by 52%), root viability (by 44%), and root length (by 50%) under salinity stress. Moreover, total soluble protein, chlorophyll pigments, the concentration of superoxide dismutase (SOD), catalase peroxidase (CAT), and ascorbic peroxidase (ASA) increased with the presence of salt concentration into the growth media and then decreased with the addition of LA + MT to saline solution. Leaf protein contents and the degradation of photosynthetic pigments were lower when LA + MT treatments were added into NaCl media. The proline and phenol contents decreased in the exogenous application of LA + MT treatments more than individual LA or MT treatments under the salinity stress. The incorporation of LA or MT or a combination of LA + MT to saline solution decreased salinity-induced malondialdehyde and electrolyte leakage. In conclusion, the alteration of metabolic pathways, redox modulation, and ions homeostasis in plant tissues by the combined LA and MT application are helpful towards the adaptation of Brassica napus L. seedlings in a saline environment. The results of this study provide, for the first time, conclusive evidence about the protective role of exogenous LA + MT in canola seedlings under salinity stress.

Seed Priming with Sulfhydral Thiourea Enhances the Performance of Camelina sativa L. under Heat Stress Conditions

“…Variety 8046 has shown better performance in relation to plant growth attributes as compared to 7126, as plant height and root length were maximum in 8046 and minimum in 7126 (Table 1). The impact of heat stress-induced damages is cultivar-specific depending on the extent of tolerance based on various tolerance mechanisms including the cellular oxidative defenses in terms of the enzymatic and nonenzymatic antioxidant compounds [58][59][60]. The endogenous content of photosynthetic pigments with CO 2 assimilation rate was also affected in heat susceptible variety (7126) as compared to heat resistant variety (8046), which is in line with the findings of [61].…”

Exogenous Application of Alpha-Lipoic Acid Mitigates Salt-Induced Oxidative Damage in Sorghum Plants through Regulation Growth, Leaf Pigments, Ionic Homeostasis, Antioxidant Enzymes, and Expression of Salt Stress Responsive Genes

“…Alpha-lipoic acid is a potent antioxidant that is soluble in both water and lipids [44]. A previous report showed that ALA can enhance growth and root formation of the salt-stressed canola seedlings [23]. This stimulation may be due to enhanced photosynthesis and carbon fixation [24].…”

“…In contrast, ALA-treated plants showed a significant enhancement in their MSI, as well as a parallel decrease in H 2 O 2 and MDA. It has been found that exogenous ALA is a potent dithiol antioxidant and can mitigate oxidative damage by scavenging ROS that are produced under diverse environmental stresses, such as high salinity [23], drought [24], heavy metals [21,25], and osmotic stress [20].…”

“…Its antioxidant capacity depends on two sulfhydryl moieties [21] which enable it to scavenge free radicals and chelate metals [22]. Under salt stress conditions, ALA was reported to mitigate oxidative damage and enhance growth and root formation of canola seedlings [23]. Moreover, exogenous ALA has been suggested to improve photosynthesis and induce tolerance mechanisms of several plant species under diverse environmental stresses [20,24,25].…”

Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms

“…Melatonin ( N -acetyl-5-methoxytrytamine, MT) is a familiar pleiotropic signaling molecule that plays a role as an antioxidant by fostering plant tolerance to various biotic and abiotic stresses [ 15 , 16 ]. MT stimulates various physiological, morphological, and biochemical features starting from seed germination to biological yield [ 17 , 18 ] by the upregulation of stress-related genes [ 17 , 19 ] that scavenge ROS and improve the antioxidant capacity of plants against abiotic stress [ 16 , 20 ]. However, despite numerous research studies, the protective effect of MT against HM stress has not been thoroughly reviewed.…”