Effect of photooxidative stress induced by paraquat in two wheat cultivars with differential tolerance to water stress

Effects of Paraquat-induced oxidative stress on antioxidants and Chlorophyll Fluorescence in stay-green wheat (Triticum aestivum L.) flag leaves

“…All the F v / F m and F' v / F' m ratios were very small with little variation at the 50, 100, and 500 µM paraquat concentrations for all three genotypes. Paraquat first affects PSI, then damages the surrounding area and PSII (Lascano et al 2003).…”

“…The homogenate was centrifuged at 16000 × g for 15 min at 4ºC. Enzyme activity was determined spectrophotometrically: SOD at 560 nm, APX at 290 nm and CAT at 240 nm, as previously described (Lima et al 2002, Lascano et al 2003.…”

Paraquat: An Oxidative Stress Inducer

“…The relationship among ROS, antioxidants, reducing equivalents, sugars, the redox state of chloroplastic and mitochondria electron transport chains are major determinants of the cellular redox state, which has a critical function in the environmental perception and modulation of defense, acclimation and tolerance responses (Foyer & Noctor, 2005 a;2005b;Lascano et al, 2003;Melchiorre et al, 2009;Robert et al, 2009). …”

“…In most plants, CuZn-SOD and Fe-SOD are present in the chloroplasts, CuZn-SOD in the cytosol and Mn-SOD in mitochondria (Casano et al, 1997;Scandalios, 1993). Degradation of H 2 O 2 , in the chloroplasts and in the cytosol is carried out by the ascorbate-glutathione cycle, which involves APX and GR activities (Lascano et al, 1999(Lascano et al, , 2003. APX has chloroplastic and cytosolic isoforms, and catalyses the conversion of H 2 O 2 to water using ascorbate as electron donor (Asada, 1999).…”

“…Paraquat treatments have been frequently used, as a potent oxidative stress inducer, in many different basic studies like: oxidative stress tolerance and cross tolerance responses associated with the antioxidant system responses (Lascano et al, 1998(Lascano et al, , 2001(Lascano et al, , 2003, forward and reverse genetic approaches to study the function of different antioxidant system components and references therein,) ROS signaling ), ROS and NO-induced cell death (Tarantino et al, 2005), and to mimic the drought effect on carbon and nitrogen metabolism of nodules (Marino et al, 2006).…”