Drought Stress Responses in Plants, Oxidative Stress, and Antioxidant Defense

Abstract

Global climate change is currently viewed as the most devastating threat to the environment, and is now gaining considerable attention from farmers, researchers, and policy makers because of its major influence on agriculture. The situation is becoming more serious due to gradual increases in the complex nature of the environment, and due to the unpredictability of environmental conditions and global climate change. One of the most acute environmental stresses presently affecting agriculture is drought, which has pronounced adverse effects on the growth and development of crop plants. The effects of drought stress are expected to increase further with increases in climate change and a growing water crisis. Drought stress usually leads to reductions in crop yield, which can result from many drought-induced morphological, physiological, and metabolic changes that occur in plants. A key sign of drought stress at the molecular level is the accelerated production of reactive oxygen species (ROS) such as singlet oxygen ( 1 O 2 ), superoxide (O 2 À ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (OH ). The excess production of ROS is common in many abiotic stresses, including drought stress, and results from impaired electron transport processes in the chloroplasts and mitochondria. One of the major causes of ROS production under drought stress is photorespiration, which accounts for more than 70% of the total H 2 O 2 produced. Plants have endogenous mechanisms for adapting to ROS production and are thought to respond to drought stress by strengthening these defense mechanisms. Therefore, enhancement of the functions of the naturally occurring antioxidant components (enzymatic and non-enzymatic) may be one strategy for reducing or preventing oxidative damage and improving the drought resistance of plants. In this chapter, we review the most recent reports on drought-induced responses in plants, focusing on the role of oxidative stress as well as on other possible mechanisms and examining how different components of the antioxidant defense system may confer tolerance to drought-induced oxidative stress.

Effects of Drought and Elevated Atmospheric Carbon Dioxide on Seed Nutrition and 15N and 13C Natural Abundance Isotopes in Soybean Under Controlled Environments

“…It was reported that the physiological processes influenced by drought can be identified by the biochemical characterization of plant tissues under stress conditions [46]. Limited research was conducted to characterize the biochemical compounds such as protein, amino acids, carbohydrates, and phenolics in the breeding program as a tool for selection, but this tool has promise in selecting for abiotic stress tolerance [24,47]. The changes of δ …”

“…Therefore, these biochemical compounds are important to understand the relationship between drought stress and drought tolerance and for decision-making when breeding for drought tolerance [23]. Since drought stress results in limiting the growth and development of the plant and consequently the supply of the photosynthate to grain during grain filling [24], the chemical composition of the grain and its quality can be affected by drought stress [12,25]. The effect of drought on seed quality could be due to the decrease of total soluble sugars especially in the grain under drought stress due to decreases in the levels of sucrose, stachyose, and verbascose.…”

Physiological adaptations to osmotic stress and characterization of a polyethylene glycol-responsive gene in Braya humilis

“…Drought also represents an oxidative stress to plants by enhancing the accumulation of reactive oxygen species (ROS) in cells, including superoxide radicals (O 2 . − ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (OH − ) [4]. These ROS can oxidize or peroxidize lipids, proteins, enzymes, pigments, and DNA, thereby further damaging the structure and function of cells, and ultimately inducing cell death [5].…”

“…To alleviate oxidative stress caused by drought, an efficient antioxidant mechanism involving nonenzymatic and enzymatic systems has evolved [7]. The former includes flavonoids, alkaloids, and phenols, whereas the enzymatic antioxidant system involves a series of enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) [4,5]. Antioxidant systems in various plant species have been studied, and antioxidant enzymes that effectively protect plants against oxidative damage induced by various biotic and abiotic stresses, including drought, have been found [4,8].…”

“…The former includes flavonoids, alkaloids, and phenols, whereas the enzymatic antioxidant system involves a series of enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) [4,5]. Antioxidant systems in various plant species have been studied, and antioxidant enzymes that effectively protect plants against oxidative damage induced by various biotic and abiotic stresses, including drought, have been found [4,8]. Drought stress research has indicated that higher antioxidant activities are detected in resistant or tolerant species/genotypes, compared with sensitive ones [9,10]; therefore, antioxidative mechanisms in drought-resistant or -tolerant species/genotypes remain a research focus [11][12][13].…”