Abstract
Plants are markedly affected by drought stress caused by fluctuations in global climate, reduction in rainfall and a decrease in soil fertility. Therefore, some mechanistic strategies to cope with adverse effects of drought stress are needed. Alpha lipoic acid (ALA), a potent antioxidant molecule, is known to function in abiotic stress tolerance. In the current study, we investigated the ALA-stimulated physiological role in tolerance to osmotic stress induced by polyethylene glycol in two maize (Zea mays L.) cultivars (cv. Helen and cv. Akpinar). Application of ALA increased the leaf water potential of maize cultivars under stressful and stress-free conditions but decreased lipid peroxidation and the hydrogen peroxide (H2O2) content. Additionally, enhanced activity of the antioxidant defense system was observed following ALA application. Exogenous ALA elevated the activities of enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR) under osmotic stress as compared to seedlings not exposed to ALA. Conversely, ascorbate peroxidase (APX) activity was decreased by ALA application in both cultivars. Higher GR and MDHAR activities of both cultivars were simultaneously observed in ALA treatments under osmotic stress. Taken together, the data indicated that exogenous ALA may function in arranging resilience against osmotic stress by reducing oxidative damage through induction of the antioxidant machinery in maize cultivars.
Highlights
Plants growing in the natural environment are often subjected to various abiotic stresses
The maize seedlings were exposed to osmotic stress for another 24 h and were divided into four groups as follows: (i) CTRL − control seedlings only exposed to Hoagland solution; (ii) PEG − osmotic stress treatment with 10% PEG6000 with -0.3 MPa as the osmotic potential; (iii) Alpha lipoic acid (ALA) − exposed to Hoagland solution containing 0.02 mM ALA; (iv) ALA+PEG − osmotic stress combined with 0.02 mM ALA
The authors indicated that enhancement of the water status and leaf surface area due to foliar application of ALA was due to its modulating role in ion homeostasis, osmotic regulation and the antioxidant system
Summary
Plants growing in the natural environment are often subjected to various abiotic stresses. Drought-affected land has increased more than two-fold in recent years, and it is considered as one of the biggest threats to agriculture in the near future. Basic agricultural practices are markedly affected by drought stress because of fluctuations in global climate, reduction in rainfall and a decrease in soil fertility. Several adaptations and mitigation strategies are required to cope with drought stress. The standard effect of drought stress is oxidative damage. Exposure to drought results in a disruption of balance between reactive oxygen species (ROS) production and removal or scavenging [1]. Overproduction of ROS is a prominent anomaly in plants under unfavorable conditions that can cause an oxidative burst, blocking plant growth and development, or even leading to death.
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