Twenty-five cultivars were initially screened for germination at 10 °C, 30 °C, and 40 °C. Four cultivars were chosen for further study for physiological and biochemical characteristics—namely, `Texas Cream 40' (TC-40), which showed ability to germinate at very high (40 °C) and low (10 °C) temperatures; `Black Crowder' (BC), which had acceptably high germination at 40 °C, but reduced germination at 10 °C; and `Mississippi Purple' (MP), which exhibited lower germination at all temperatures tested. The main sugars present in cowpea seed were sucrose, raffinose, and stachyose. Sugar contents were affected by cultivar, type of tissue, and temperature. Sucrose contents were higher in embryo tissue of cultivars with a lower germination percentage, and reduced in the cultivar with a higher germination percentage, suggesting the use of sucrose for germination. Sucrose decreased greatly at 30 °C and increased again at 40 °C. Sucrose “de novo” synthesis was higher at higher temperature. An accumulation of sucrose was evident in embryo tissues of cultivars with reduced ability to germinate at low temperature. Raffinose and stachyose contents were higher in ungerminated seed. In germinated seed, raffinose and stachyose contents were found only in cotyledon tissues at 10 °C. The peroxidase activity was affected by cultivars, type of tissue, and temperature. The highest peroxidase activity was found at low temperature (10 °C) in embryo tissue of the cultivar with the highest germination. The result also suggests that high peroxidase activity was related to ability of seed to germinate at low temperature.
Shahidul Islam, Carmen Rafaela, and James Garner
Mozhgan Zangeneh and Hassan Salehi
), peroxidase (POX), and an amino acid (proline) in plant cells ( Rahimizadeh et al., 2007 ). Information about the significant morpho-physiological characteristics of Narcissus accessions can be applied to breeding programs to detect accessions resistant to
Zohar Shaham, Amnon Lers, and Susan Lurie
`Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] were harvested in two seasons and stored at 0 °C air storage with no pretreatment (control), after heating for 4 d at 38 °C, or after treating for 16 hours at 20 °C with 1 μL·L-1 1-methylcyclopropene (1-MCP). The effects of the two treatments on superficial scald development were consistent over both seasons. Scald began to appear after 8 weeks in control fruit, after 16 weeks in heated fruit but not on 1-MCP treated fruit. α-Farnesene accumulation and oxidation were slower in the skin of heated than in control fruit, and almost entirely absent in 1-MCP treated fruit. The activities of five antioxidant enzymes, ascorbate peroxidase, catalase, glutathione reductase, peroxidase and superoxide dismutate, were measured at two-week intervals in the apple peel, quantitatively as total activity and qualitatively by isozyme analysis. Enzyme activities either increased or remained stable during 16 weeks of storage, except for superoxide dismutase activity, which decreased. Ascorbate oxidase activity was higher in heated than control apples and there was an additional peroxidase isozyme present in activity gels. The activities of antioxidant enzymes were lower in 1-MCP treated fruit except for catalase during the first month of storage. Lipid soluble antioxidant activity was higher in 1-MCP treated fruit than the fruit of the other treatments, and water soluble antioxidant activity was higher in both treatments than in control fruit during the time that scald was developing in control apples. Both free and total phenol contents in the peel fluctuated during storage but no consistent trend was detected. The differences in enzyme activity and antioxidant content of the peel of 1-MCP and heated apples may play a role in preventing or delaying the appearance of superficial scald.
A.R. Dixon, R.B. Boone, A. Gardea, L.S. Daley, and T.L. Righetti
A microcomputer-based image processing system was used to simplify the large number of visual comparisons required to identify various Corylus spp., cultivars, and clonal accessions using polyacrylamide gel electrophoresis isozyme patterns. Photographs of gels stained for peroxidase, acid phosphatase, and phenol oxidase were digitally captured and selected lanes were enhanced and scanned. The scan data were analyzed to locate bands and normalize their position to that of standards. Such data were plotted and a computer-generated isozyme pattern was displayed. Compressed image data were then stored in a database for subsequent automated isozyme pattern comparisons. Photographic records that were previously used in published reports were reevaluated with the computerized system. Species, cultivars, or clones that were characterized in visual evaluations were similarly characterized using the computer method. Computer evaluations usually identified more bands. Band positions were only rarely different and probably resulted from better normalization relative to standard bands when using the computerized procedure.
Naoki Yamauchi and Alley E. Watada
Degradation of chlorophyll in spinach (Spinacia olearacea L. cv. Hybrid 612) appeared to be regulated through the peroxidase-hydrogen peroxide pathway, which opens the porphyrin ring, thus resulting in a colorless compound. This conclusion was arrived at from the analysis of chlorophylls (Chls) and their metabolizes by HPLC and of enzyme activities catalyzing the degradative reactions. Chls decreased at 25C but not at 1C. The chlorophyll oxidase pathway was not active, as noted by the lack of accumulation of a reaction product named Chl a-1. Lipid peroxidation increased with storage, but the products of the reaction. did not degrade chlorophyll, as noted by the lack of increase in Chl a-1. Chlorophyllase activity increased, but chlorophyllide, the expected product of the reaction, changed minimally during senescence. Ethylene at 10 ppm did not alter the pathway that degraded chlorophyll in spinach.
Mulpuri V. Rao, Christopher B. Watkins, Susan K. Brown, and Norman F. Weeden
Fruit from seedlings selected from a population obtained by crossing superficial scald-resistant `White Angel' and superficial scald-susceptible `Rome Beauty' apple (Malus ×domestica Borkh.) were used to investigate the role of oxidative processes in the development of superficial scald. Selections were identified for study based on fruit coloration and scald susceptibility. Plant material had one of the following three physiognomies: 1) red-skinned fruit resistant to scald; 2) red-skinned fruit susceptible to scald; and 3) yellow-skinned fruit susceptible to scald. The concentrations of α-farnesene, conjugated triene (CT) species, hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances, carbonyl groups, and the activities of superoxide dismutase, guaiacol-peroxidase, and catalase were measured at harvest and during 0.5 °C storage. Relationships were poor between scald susceptibility and α-farnesene and its oxidation products, CT258, CT281, and the CT258/CT281 ratio. Tissue concentrations of H2O2 were lower in scald-resistant than in scald-susceptible fruit at harvest and after storage, and these lower concentrations were associated with less damage to cellular membranes (lipid peroxidation) and proteins (carbonyl group content). Higher activities of the H2O2-degrading enzymes, guaiacol-peroxidases, and catalases, were related to lower H2O2 content and lower scald susceptibility. Activities of superoxide dismutase, a H2O2-generating enzyme, were not related to scald susceptibility or storage period. We hypothesize that fruit susceptibility to scald is strongly influenced by cellular efficiency in metabolizing active oxygen species such as H2O2.
Sandra L. Anagnostakis
M. Landrigan, S.C. Morris, and K.S. Gibb
The effect of enzymic action, mechanical damage, and relative humidity (RH), on browning of stored rambutan was investigated. Mature rambutan fruit (`R 134') were infiltrated with known enzyme inhibitors, then either mechanically damaged or left undamaged, before storage at 20 °C with 95% or 65% RH. Fruit were visually scored for browning and weight loss was measured. All fruit at low RH browned severely. At high RH, infiltration with water, but not with the enzyme inhibitors, salicylhydroxamic acid and catalase, led to a large increase in browning. We infer that enzymes were involved in browning in damaged tissue under high RH. At low RH, inhibitors were ineffective as desiccation was the dominant causative factor of browning.
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
Azadeh Behrooz, Kourosh Vahdati, Farhad Rejali, Mahmoud Lotfi, Saadat Sarikhani, and Charles Leslie
, starch, and total phenolic content, and peroxidase enzyme activity were determined. The relative amount of chlorophyll was measured using an SPAD 502 (Konica Minolta, Inc., Japan). Total soluble sugar and starch contents of leaves were extracted with 80