Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants

Heavy metals in soils

Unravelling cadmium toxicity and tolerance in plants: Insight into regulatory mechanisms

Abiotic stresses (such as metals/metalloids, salinity, ozone, UV-B radiation, extreme temperatures and drought) are among the most challenging threats to agricultural system and economic yield of crop plants. These stresses (in isolation and/or combination) induce numerous adverse effects in plants, impair biochemical/physiological and molecular processes, and eventually cause severe reductions in plant growth, development and overall productivity. Phytohormones have been recognized as a strong tool for sustainably alleviating adverse effects of abiotic stresses in crop plants. The significance of salicylic acid (SA) has been increasingly recognized in improved plant abiotic stress-tolerance via SA-mediated control of major plant-metabolic processes. However, the basic biochemical/physiological and molecular mechanisms that potentially underpin SA-induced plant-tolerance to major abiotic stresses remain least discussed. Based on recent reports, this paper: (a) overviews historical background and biosynthesis of SA under both optimal and stressful environments in plants; (b) critically appraises the role of SA in plants exposed to major abiotic stresses; (c) cross-talks potential mechanisms those are expected to govern SA-induced plant abiotic stress-tolerance; and finally (d) briefly highlights major aspects so far unexplored in the current context.

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Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants

In a persistently changing environment, plants are constantly challenged by various abiotic stresses such as salinity, drought, temperature extremes, heavy metal toxicity, high-light intensity, nutrient deficiency, UV-B radiation, ozone, etc. which cause substantial losses in the yield and quality of a crop. A key sign of such stresses at the molecular level is the accelerated production of reactive oxygen species (ROS) such as singlet oxygen (1O2), superoxide (O2•−), hydrogen peroxide (H2O2) and hydroxyl radicals (OH•). ROS are extremely reactive in nature because they can interact with a number of cellular molecules and metabolites, thereby leading to irreparable metabolic dysfunction and death. Plants have well-developed enzymatic and non-enzymatic scavenging pathways or detoxification systems to counter the deleterious effects of ROS that include the enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPX) and peroxidases (POX) as well as non-enzymatic compounds such as ascorbate (AsA), glutathione (GSH), carotenoids and tocopherols. In plant cells, specific ROS-producing and scavenging systems are found in different organelles and the ROS-scavenging pathways from different cellular compartments are coordinated. Recent studies in plants have shown that relatively low levels of ROS act as signaling molecules that induce abiotic stress tolerance by regulating the expression of defense genes. Additionally, numerous results have shown that plants with higher levels of antioxidants, whether constitutive or induced, showed greater resistance to different types of environmental stresses. In this chapter we attempt to summarize recent researches on the mechanisms and possible regulatory roles of ROS in abiotic stress tolerance. Further, we discuss the progress made during the last few decades in improving the oxidative stress tolerance of plants through genetic engineering by different components of ROS detoxification systems in plants.

Plant Response and Tolerance to Abiotic Oxidative Stress: Antioxidant Defense Is a Key Factor

Photosynthetic activity, pigment composition and antioxidative response of two mustard (Brassica juncea) cultivars differing in photosynthetic capacity subjected to cadmium stress.

Role of nanomaterials in plants under challenging environments.

Polysaccharide from Plantago as a green corrosion inhibitor for carbon steel in 1M HCl solution.

Nitric oxide-induced synthesis of hydrogen sulfide alleviates osmotic stress in wheat seedlings through sustaining antioxidant enzymes, osmolyte accumulation and cysteine homeostasis.

The success of sustainable food production greatly relies on the widespread use of mineral fertilizers. However, the commercially available fertilizers are blended with a range of trace metals, which are introduced in to the soil along with the application of fertilizers. Given the rising environmental concern, the interest in eco-friendly organic inputs to the soils has grown manifold. The additions of recycled organic fertilizers to the soils have been proposed as a substantially beneficial input in place of inorganic fertilizers. However, the application of organic fertilizers may result in the heavy metal enrichment of soil and imbalanced nutrient availability. Additionally, according to one estimate, only about half of the applied fertilizers are being utilized by the plants while the remaining unutilized fertilizers could enter the soil surface and water bodies and may affect the environment adversely. The major environmental concern includes the eutrophication of fresh water bodies and enrichment of the soil with toxic heavy metals and radionuclides. In the present article, in addition to highlighting the consequences of large-scale fertilizer inputs on soil health, the impact on water bodies is also discussed.

Mohammad Mobin

Papers

Photosynthetic activity, pigment composition and antioxidative response of two mustard (Brassica juncea) cultivars differing in photosynthetic capacity subjected to cadmium stress.

Role of nanomaterials in plants under challenging environments.

Polysaccharide from Plantago as a green corrosion inhibitor for carbon steel in 1M HCl solution.

Nitric oxide-induced synthesis of hydrogen sulfide alleviates osmotic stress in wheat seedlings through sustaining antioxidant enzymes, osmolyte accumulation and cysteine homeostasis.

Fertilizers and Their Contaminants in Soils, Surface and Groundwater