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    Induced anti-oxidant activity in soybean alleviates oxidative stress under moderate boron toxicity
    (SPRINGER, 2013) Hamurcu, Mehmet; Sekmen, Askim Hediye; Turkan, Ismail; Gezgin, Sait; Demiral, Tijen; Bell, Richard W.
    The effect of B toxicity on antioxidant responses of soybean (Glycine max) cv. Athow was investigated by growing plants for 43 days at 0.2 (control), 2 and 12 mg B kg(-1). At the end of the treatment period, shoot growth, lipid peroxidation level, the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), and their isoenzymes in leaves were measured. Boron concentration in leaves was significantly increased by the increasing levels of B treatment from 43 to 522 mg kg(-1), and shoot dry matter was depressed at 12 mg B kg(-1). Significant increases in SOD, CAT, and APX activities were determined in leaves under 12 mg B kg(-1); however, GR activities were decreased while POX activity was unchanged. Increased enzymic antioxidant activity arose from a combination of newly formed isoenzymes and activation of existing isoenzymes. By contrast, SOD and GR activities were decreased by 2 mg B kg(-1) concentration as compared to the control groups while POX activity was increased and the activity of CAT did not change. Malondialdehyde content increased under 2 mg B kg(-1) but decreased under 12 mg B kg(-1). These results suggest that higher antioxidant activity observed under 12 than at 2 mg B kg(-1) provided higher free radical-scavenging capacity, and thus a lower level of lipid peroxidation in Athow. While the induction of increased antioxidant activity was related to internal boron levels, the signaling and coordination of responses remain unclear.
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    Oxidative stress responses in watermelon (Citrullus lanatus) as influenced by boron toxicity and drought
    (LITHUANIAN RESEARCH CENTRE AGRICULTURE & FORESTRY, 2015) Hamurcu, Mehmet; Demiral, Tijen; Hakki, Erdogan Esref; Turkmen, Onder; Gezgin, Sait; Bell, Richard W.
    This study aimed to investigate the effect of different boron (B) treatments on drought tolerance of watermelon plants. Drought tolerant Citrullus lanatus (Thunb.) Matsum. et Nakai genotype 'Kar 98' was grown in controlled greenhouse conditions hydroponically and exposed to drought stress by applying PEG 6000 (polyethylene glycol) in the presence of three boron dosages: 0.05, 0.25 and 1.25 mM. Growth parameters (fresh weight, dry weight and lengths of shoot and roots), leaf relative water content, boron accumulation, lipid peroxidation level and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) enzymes were determined as well as the accumulation of hydrogen peroxide (H2O2) and hydroxyl (center dot OH)-scavenging activity were assayed. Increasing dosages of boron alone caused more severe growth reduction than combined with PEG 6000-induced drought stress. Induced drought stress caused less accumulation of boron in leaves and roots. B concentration of 1.25 mM caused lipid peroxidation in a reactive oxygen species-independent manner and drought stress-induced lipid peroxidation was alleviated by increasing B dosages. Induced glutathione reductase activity under the combination of 1.25 mM B and PEG 6000-induced drought stress seemed an important physiological response in 'Kar 98' plants against multiple stresses.