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

same minimum structure used for A. thaliana . However, this cultivar is poorly characterized, particularly when antioxidant enzymes are concerned. Such basic information is essential and will help to improve our understanding about some of the basic

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Michelle DaCosta and Bingru Huang

nonenzymatic components that can be divided into two different types of repair mechanisms: 1) production of antioxidants or antioxidant enzymes that directly react with and scavenge AOS, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase

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Huiying Li, Hongji Luo, Deying Li, Tao Hu and Jinmin Fu

antioxidant enzymes including SOD, glutathione peroxidase (GPX), ascorbate peroxidase (APX), GR, and CAT were found in coontail ( Ceratophyllum demersum ) when exposed to Pb ( Mishra et al., 2006 ). On the contrary, there were also reports indicating decreased

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Chang-Xia Du, Huai-Fu Fan, Shi-Rong Guo and Takafumi Tezuka

resulted in an increase in polyamine and proline contents and antioxidant enzyme activities in cucumber seedlings, which contributed osmotic adjustment during salinity ( Duan et al., 2008 ). In water-stressed cucumber plants, Kubiś (2008) showed that

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Lixin Xu, Liebao Han and Bingru Huang

, and cytosolic APX ( Shigeoka et al., 2002 ; Yoshimura et al., 2001 ). Previous studies have indicated that higher activity levels of antioxidant enzymes may contribute to better drought tolerance by increasing the protection capacity against oxidative

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Yali He and Bingru Huang

, consequently, membrane injury, protein degradation, and enzyme inactivation ( Meriga et al., 2004 ; Sairam et al., 2000 ). Intracellular membrane damage due to ROS can cause pigment breakdown ( Scandalios, 1993 ). Multiple antioxidant enzyme systems are

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Suping Zhou, Roger J. Sauvé, Margaret T. Mmbaga and Chaim Frenkel

Leucanthemum maximum `Silver Princess' plants, that were gradually acclimated for 7 days at 10 °C followed by 28 days at 7 °C, were subjected to the following cold treatments: 30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C to identify cold inducible proteins that may be responsible for cold tolerance in this cold tolerant species. Change in antioxidant enzymes activity in fully expanded leaves was assessed after each treatment. Catalase activity began to increase after 30 days at 4 °C and reached its peak after a 5-day exposure to 0 °C. The activity of cellular glutathione peroxidase and glutathione reductase significantly increased after a 4-day exposure to 0 °C. Changes in activity of four active superoxide dismutase isoforms, one basic guaiacol peroxidase and two o-dianisine peroxidase isoforms were also detected following the full series of cold treatments (30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C).

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Zhaolong Wang, John Pote and Bingru Huang

This study was designed to examine whether shoot injury induced by high root-zone temperature is associated with changes in shoot detoxifying metabolism and to determine the level and duration of high root-zone temperatures that would induce physiological changes in two cultivars of creeping bentgrass (Agrostis stolonifera var. palustris Huds) differing in heat tolerance. Plants of `Penn A-4' (heat tolerant) and `Putter' (heat susceptible) were grown in sand and exposed to root-zone temperatures of 20 (control), 21, 22, 23, 25, 27, 31, and 35 °C in water baths while air temperature was maintained at 20 °C in a growth chamber. Turf quality, leaf cytokinin content, and antioxidant enzyme activities declined at increased soil temperatures and the duration of treatment for both cultivars. A decline in turf quality occurred following 40 days of exposure to 35 °C for `Penn A-4' and 26 days of exposure to 31 °C for `Putter'. The root-zone temperature causing the decline of isopentenyl adenosine and zeatin cytokinins was 25 °C at 37 d for `Putter' and 27 °C at 47 days for `Penn A-4'. The temperature causing the decline of superoxide dismutase and catalase activities was 25 °C and 27 °C at 33 days for `Putter' and 27 °C and 31 °C at 43 days for Penn A-4, respectively. Malondialdehyde content increased at 27 °C for `Putter' and 31 °C for `Penn A-4' at 43 days of treatment. The decline in cytokinin content and antioxidant enzyme activity occurred at a lower soil temperature and earlier during the treatment than the decline in turf quality, possibly contributing to turf quality decline. The root-zone temperatures causing the decline in turf quality, cytokinin content, and oxidative damage were higher in the heat-tolerant cultivar than heat-susceptible cultivar.

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Sunita Kochhar, Christopher B. Watkins, Patricia L. Conklin and Susan K. Brown

The activities and isoenzyme patterns of guaiacol-dependent peroxidase (POX), ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT) were studied in yellow- and red-fruited crab apple [Malus (L.) Mill.] selections from a `White Angel' × `Rome Beauty' cross that show differential susceptibility to the physiological storage disorder, superficial scald. There were no consistent relationships between total enzyme activities and scald incidence, high activities of the enzymes being detected in selections with both high and low susceptibilities to scald. However, additional individual isoforms of some antioxidant enzymes were detected in the scald-resistant selections when compared with scald-susceptible selections. In a native gel system, four guaiacol-dependent POX isoenzymes were detected in both yellow and red scald-resistant selections compared with only two in scald-susceptible selections. Similarly, for anodic acidic POX assayed using benzidine, six isoenzymes were detected in both yellow and red scald-resistant selections compared with five in yellow and four in red susceptible selections. Ten SOD isozymes were detected in scald-resistant yellow-fruited selections compared with only five faint bands in scald-susceptible selections, but similar patterns were not detectable for red-fruited selections. Differences in the presence of various isoenzymes for CAT and APX were also detected among the selections, but associations with scald susceptibility were also affected by fruit color or were inconsistent. The presence or absence of individual isoenzymes may be a better indication of scald resistance or susceptibility than the total enzyme activities. Isoenzyme analyses, especially of POX, could be useful to breeders for the early detection of scald resistance/susceptibility in apples.

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Hongmei Du, Zhaolong Wang and Bingru Huang

apparatus, leading to degradation of chlorophyll ( Foyer et al., 1994 ; Smirnoff, 1993 ). Plants use ROS scavenging mechanisms to protect cells from oxidative injury, including the activation of antioxidant enzymes: superoxide dismutase (SOD), which convert