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Kanogwan Kerdnaimongkol and William R. Woodson

A. Frugoli for providing the catalase isozyme gel analysis protocol. We are also grateful to Greg Martin for advice regarding genetic analysis of antisense plants. The cost of publishing this paper was defrayed in part by the payment of page charges

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Dennis J. Werner

Catalase isozymes were examined in a wide range of peach [Prunus persica (L.) Batsch] cultivars representing historical U.S. cultivars, commercial cultivars from numerous North American breeding programs, and the peach plant introduction (PI) collection. All historical peach cultivars from the United States and those released from commercial breeding programs were fixed for the slow (Cat l-2) allele, with the exception of `Belle of Georgia', `Honeyglo' nectarine, and various cultivars from the Univ. of Florida breeding program, which possessed a fast-migrating (Cat 1-l) allele in homozygous or heterozygous state. Polymorphism was revealed in the 51 peach PI clones examined, with allelic frequencies of 0.69 and 0.31 for the Cat l-2 and Cat l-1 alleles, respectively. Most PIs that originated directly from China were homozygous Cat l-l/Cat l-l, while most PI clones introduced from Europe were homozygous Cat l-2/Cat l-2. Examination of the catalase genotype of cultivars previously proposed as the possible male parent of `Belle of Georgia' (`Champion', `Early Crawford', `Late Crawford', `Oldmixion Free', and `Stump-the-World') revealed that none of these cultivars could have been the male parent of `Belle of Georgia'. Segregation data from various peach crosses was consistent with the hypothesis that catalase polymorphism could be explained by the presence of two alleles at a single locus.

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Jeff Anderson

Activated forms of oxygen, including hydrogen peroxide, have been implicated in plant responses to stress. Environmental stresses may increase prooxidants, impair defense systems, or both. Stress acclimation may involve changes in capacity or stability of activated oxygen defenses. Catalases and peroxidases are the primary enzymatic detoxifiers of hydrogen peroxide in most plant tissues. Pepper leaf disks treated with hydrogen peroxide solutions from 0 to 100 mM showed increased electrolyte leakage and ethylene and methanol evolution with increasing concentration, but changes were slight compared to freeze-killed tissues. Data suggested that pepper leaves had considerable capacity to detoxify hydrogen peroxide. Cellular damage in heat-stressed tissues occurred over a similar temperature range that catalase activity declined. Leaf disks exposed to 24 to 59 °C for 15 min exhibited a sigmoidal electrolyte leakage response curve with an inflection at 51.5 °C. A similar plot of catalase activity vs. temperature exhibited an inflection point at 53.1 °C. Thermotolerance of plants exposed to the acclimating regime of 38 °C day/30 °C night increased from 50.7 to 53.9 °C based on electrolyte leakage. Catalase activity also showed an adaptive response with the inflection point increasing from 52.6 to 56.8 °C. It appears that catalase activity remains stable to a higher temperature in acclimated leaves, with similar activity in nonstressed control and acclimated plants.

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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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Yali He and Bingru Huang

substrates, and it is therefore likely to be central in the defense mechanism ( Bowler et al., 1992 ). Hydrogen peroxide is scavenged by catalase (CAT) and peroxidases, which convert hydrogen peroxide to water and molecular oxygen ( Bowler et al., 1992

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Pedro Novillo, Alejandra Salvador, Pilar Navarro and Cristina Besada

., 2003 ). The ROS metabolism is controlled by an array of interrelated enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD), which act concomitantly with nonenzymatic antioxidants; O 2 − is

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Jorge H. Siller-Cepeda, Leslie Fuchigami and Tony H. H. Chen

Many seeds of woody plants require low temperature or other treatments to overcome dormancy. Changes in catalase activity and glutathione has been proposed to be associated with the breaking of dormancy. We examined the level of glutathione and catalase activity of cherry seeds (Prunus mahaleb cv. Lambert) exposed to several dormancy breaking agents. Seeds imbibed in water for 24 hrs. were either stratified at 4°C or at 25°C for up to 12 weeks, or exposed to other dormancy breaking agents. Germination test, glutathione and catalase activity were determined weekly and/or after treatment. Analysis of levels and state of glutathione were performed by high pressure liquid chromatography (HPLC), and catalase activity was assayed spectrophotometrically. Total glutathione in dry and imbibed seeds were similar, but, ratio between the reduced and oxidized form were different. Low temperature stratification for 12 weeks increased the reduced form of glutathione six-fold, while percent germination increased up to 94%.

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Jorge H. Siller-Cepeda, Leslie Fuchigami and Tony H. H. Chen

Many seeds of woody plants require low temperature or other treatments to overcome dormancy. Changes in catalase activity and glutathione has been proposed to be associated with the breaking of dormancy. We examined the level of glutathione and catalase activity of cherry seeds (Prunus mahaleb cv. Lambert) exposed to several dormancy breaking agents. Seeds imbibed in water for 24 hrs. were either stratified at 4°C or at 25°C for up to 12 weeks, or exposed to other dormancy breaking agents. Germination test, glutathione and catalase activity were determined weekly and/or after treatment. Analysis of levels and state of glutathione were performed by high pressure liquid chromatography (HPLC), and catalase activity was assayed spectrophotometrically. Total glutathione in dry and imbibed seeds were similar, but, ratio between the reduced and oxidized form were different. Low temperature stratification for 12 weeks increased the reduced form of glutathione six-fold, while percent germination increased up to 94%.

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Hening Hu and Gary A. Couvillon

The activities of catalase and of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), the two key enzymes in the pentose phosphate pathway (ppp), were measured in the seeds of Prunus persica (L.) Batsch var. nectarina Maxim `Nectarine 7'. The seeds were subjected to three imbibition treatments: 1) continuous 24C; 2) continuous 4C; and 3) application of thiourea (TU)/gibberellic acid (GA) at various concentrations to seed held at 24C then subsequently chilled at 4C. Treatments of continuous 24 or 4C indicated that catalase, G6PDH, and 6PGDH exhibited significant activity increases only when the seeds obtained germination potential, which occurred in the seeds chilled for 7 weeks at 4C. Seeds held at 24C did not germinate and showed little change with time in G6PDH and 6PGDH activity. There was only a slight increase in catalase activity beginning 3 weeks following treatment initiation and a decrease in activity following 13 weeks of treatment. Thiourea treatment resulted in an inhibition of catalase activity and a stimulation of G6PDH, but had no effect on 6PGDH activity. However, no correlation between enzymic activity and seed germination was found. The results strongly questioned the role of the ppp and catalase activity in dormancy control as previously hypothesized.

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Steven A. Altman and Theophanes Solomos

Sim-type carnation flowers (Dianthus caryophyllus L., cv. Elliot's White) continuously treated with 50 mM or 100 mM 3-amino-1,2,4-triazole (amitrole) and held in the dark at 18°C did not exhibit a respiratory climacteric relative to dH2O-treated controls. No morphological changes symptomatic of floral senescence appeared in treated flowers until 12-15 days post-harvest. Other triazoles were not effective in prolonging senescence. Amitrole appears to inhibit ethylene biosynthesis by blocking the enzyme-mediated conversion of S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylate. Ethylene action appears to be progressively inhibited in that flowers held in treatment solution for 2 d or less responded to application of 10 uL/L exogenous ethylene whereas flowers held 10 d or longer exhibited no response. Electrophoretic resolution of total crude extracts evidenced protein synthesis as well as degradation. Western analysis and total activity assays showed an amitrole concentration-specific inhibition of catalase activity.