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Chen Chen, Meng-Ke Zhang, Kang-Di Hu, Ke-Ke Sun, Yan-Hong Li, Lan-Ying Hu, Xiao-Yan Chen, Ying Yang, Feng Yang, Jun Tang, He-Ping Liu, and Hua Zhang

superoxide dismutases (SOD) activity in Δ sodC mutant. ( A ) Confirmation of sodC deletion mutant by polymerase chain reaction (PCR) analysis of genomic DNA from wild type Aspergillus niger MA 70.15 and Δ sodC . Lane 1 and 2, genomic PCR of A. niger MA

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S.M. Lutfor Rahman, Wayne A. Mackay, Eiji Nawata, Tetsuo Sakuratani, A.S.M. Mesbah Uddin, and Bruno Quebedeaux

Effects of water stress on superoxide dismutase (SOD) activities, changes in protein content, leaf water potential (Ψl) and growth were studied in drought-sensitive Kyokko (KK) and Ratan (RT), and drought-tolerant TM 0126 (TM) and VF-134-1-2 (VF) cultivars of tomato (Lycopersicon esculentum Mill.) in order to obtain fundamental information for breeding drought tolerant cultivars that may be adapted to water stress in many parts of the world. Growth of drought-tolerant TM and VF was greater than that of drought-sensitive KK and RT under water stress conditions. Leaf water potential (Ψl) decreased by water stress treatments in all the cultivars, but the reduction was much more rapid and pronounced in KK and RT than VF and TM. Ψl of stressed cultivars decreased by 30% to 40% compared to the untreated control cultivars. The initial reduction in the range of 20% to 35% was more rapid in KK and RT than TM and VF. SOD activities were increased by water stress in all cultivars. Increase of SOD activities by water stress was much more rapid and pronounced in TM and VF than in KK and RT. Leaf protein concentration was decreased by the water stress treatments in all cultivars evaluated. In KK and RT, much more rapid reductions in protein concentration were observed than in TM and VF. The regression analysis of Ψl and SOD suggest the possibility to using SOD activities as an additional screening criterion for tomato drought tolerance improvement.

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Shiow Y. Wang, Miklos Faust, and Hong J. Jiao

The effects of thidiazuron on changes in superoxide dismutase (SOD) activity in apple (Malus domestica Borkh cv. York Imperial) buds during dormancy break were determined. Dormant buds had low SOD activity. Increased SOD activity was correlated with budbreak induced by thidiazuron. Buds contained three distinct forms of SOD: Cu, Zn-SOD; Mn-SOD; and Fe-SOD. Most of the SOD activity in apple buds was attributed to Cu and Zn-SOD, followed by Mn-SOD. Iron-SOD was not present in dormant buds, and only a trace amount was found as buds started rapid expansion. Chemical name used: N-phenyl-N′-1,2,3,-thidiazol-5-ylurea (thidiazuron).

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Nadeem A. Abbasi and Mosbah M. Kushad

Peroxidase (POD), polyphenoloxidase (PPO), and superoxide dismutase (SOD) activities were measured during several phases of bud development, ripening, and storage of `Oregon Spur Red Delicious' (Malus domestica Borkh) apple fruit. POD, PPO, and SOD activities were significantly altered as a result of bud development. At the early stages of fruit development, the activities of these enzymes were significantly higher, then declined as the fruit increased in size. The activities of these enzymes declined as the fruit reached full maturity. Fruits harvested 3 weeks before commercial maturity and stored for up to 6 months have higher enzyme activities than fruits harvested at or beyond commercial maturity. The activities of these enzymes in relation to fruit firmness, soluble solids, and ethylene will be determined and related to overall fruit quality.

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Chien Yi Wang

The activities of catalase and superoxide dismutase decreased while peroxidase activity increased in zucchini squash (Cucurbita pepo L., cv. `Elite') during storage at 5°C. Preconditioning of squash at 15°C for 2 days prior to the cold storage reduced the decline of catalase activity and suppressed the increase in peroxidase activity. The superoxide dismutase activity remained higher in temperature conditioned squash than in untreated squash. These results indicate that acclimation to chilling temperature in squash may also involve modifications in the activities of catalase, peroxidase, and superoxide dismutase.

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Xunzhong Zhang and R.E. Schmidt

Superoxide dismutase (SOD) activity is closely associated with stress tolerance of creeping bentgrass [Agrostis stoloniferous L. var. palustris (Huds.) Farw (syn. A. palustris Huds.)]. This study was conducted to investigate the influence of two plant growth regulators (PGRs) on the endogenous antioxidant SOD level and photochemical activity in `Penncross' creeping bentgrass grown under two fertilizer regimes. Mature `Penncross' was treated monthly with TE at 0.44 g a.i./100 m2 and PPC at 3.37 g a.i./100 m2 from May through November at the Virginia Tech Turfgrass Research Center, Blacksburg, Va. Foliar application of TE and PPC increased SOD activity, photochemical activity, and Fm730/Fm690 ratio of creeping bentgrass under the two fertilization regimes as well as when the grass was exposed to a low soil moisture environment. TE reduced clipping weight consistently regardless of the fertilization regime. In contrast, PPC increased clipping weight slightly. Both TE and PPC significantly reduced Dollar spot disease (Sclerotinia homoeocarpa Bennett) under both high and low fertilization regimes. No significant fertilization × PGR interactions for SOD, photochemical activity of PS II, and Fm730/Fm690 were observed in well-watered or drought stressed bentgrass. Improvement in stress tolerance of creeping bentgrass by the PGRs appears to be associated partially with an increase of endogenous SOD activity. Chemical names used: trinexapac-ethyl (TE); propiconazole (PPC).

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Priscila L. Gratão, Carolina C. Monteiro, Lázaro E.P. Peres, and Ricardo Antunes Azevedo

have concentrated our attention on some of the key antioxidant enzymes such as catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), glutathione reductase (GR), and superoxide dismutase (SOD). The Micro-Tom cultivar was kindly

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Xunzhong Zhang and Erik H. Ervin

possess various means of tolerating or avoiding ultraviolet-B stress ( Caldwell et al., 1983 ). Antioxidants are important ultraviolet-B plant defense mechanisms. Antioxidants such as superoxide dismutase (SOD) function to scavenge reactive oxygen species

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Yali He and Bingru Huang

involved in the enzymatic scavenging of ROS. Superoxide dismutase (SOD) is the enzyme for O 2 scavenging in the first step of ROS metabolism ( Elstner, 1982 ). Its activity determines the concentrations of O 2 and H 2 O 2 , the two Haber-Weiss action

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Xunzhong Zhang, Erik H. Ervin, Yiming Liu, Guofu Hu, Chao Shang, Takeshi Fukao, and Jasper Alpuerto

conditions, plants have developed a series of detoxification systems that break down the highly toxic ROS ( Wang et al., 2012 ; Zhang and Kirkham, 1996 ; Zhang et al., 2012 ). Superoxide dismutase has been considered as the first line of defense against ROS