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Mitiku Girma and Alex I. Smirnov

Recent studies performed at the Univ. of Sheffield (Sheffield, England) have established a correlation between the onset of senescence and the loss of viability in plants with a development of stable free-radicals that can be observed by Electron Paramagnetic Resonance (EPR) spectroscopy. We explored the possibility of free-radical formation following root injury of corn seedlings (Zea mays L.). Free radical signals were detected by EPR spectroscopy at 9.5 GHz. In all cases, we observed a single-line free-radical signal (g value ≈2.004) superimposed with six-line EPR spectrum from Mn2 + ions naturally present in the plant tissues. We determined a consistent increase in the intensity of single-line EPR signal after inducing root injury. This signal presumably is attributed to a quinone-derived radical and, as speculated, is associated with stressed respiratory transport chains. Based on our results, we suggest that free-radical reactions can be induced by root injury. Furthermore, an appearance of free-radical signal in the root may serve as an indication of a stress, natural and induced. If the precursors of observed free-radical signal can be determined, this will provide better insight on free-radical processes in plants followed by an injury. This work used the resources of the Illinois EPR Research Center (NIH P4 1 -RR0 1811).

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Nadeem A. Abbasi, Mosbah M. Kushad, and Anton G. Endress

Superoxide dismutase (SOD: EC and peroxidase (POD: EC activities were evaluated during maturity, ripening, and senescence of `Red Spur Delicious' (Malus domestica Borkh.) apple fruits. SOD and POD activities did not exhibit uniform changes during fruit maturity; however, during fruit ripening, activities of both enzymes increased significantly. During fruit senescence, SOD activity continued to increase, while POD activity declined by 24% to 50%. Fruit maturity at harvest significantly affected SOD and POD activities during the progression of ripening and senescence. SOD activity was significantly higher during ripening and senescence of fruits that were harvested at full and over-mature stages than in fruits harvested at early mature stage. In contrast, POD activity was lower in fruits that were harvested at full and over-mature stages than in fruits harvested at early mature stage. Increase in SOD and POD activities during fruit ripening suggest that these enzymes are actively involved in scavenging free-radicals generated during this developmental stage. However, the decline in POD activity during fruit senescence suggest a possible disruption of the breakdown of H2O2 free-radicals. This disruption may have contributed to tissue senescence and the induction of a physiological disorder called senescence scald.

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R. Aynaou, F.M. Woods, R. Shewfelt, J.E. Brown, S. Tuzun, J.H. Cherry, and L.G. Sanders

The ability of two tomato cultivars, Lycopersicon esculentum cv. VFNTCherry (chill sensitive) and L. esculentum × L. pimpinellifollim cv. New York 280 (chill tolerant) to acclimate to low temperature storage at 2 °C were compared following prior temperature preconditioning. The activities of catalase, peroxidase, and superoxide dismutase and electrolyte leakage were monitored during a 15-day preconditioning period. Low temperature preconditioning reduced membrane damage in both fruit. In contrast, high temperature preconditioning accelerated the rate of leakage in VFNT, while fruit of NY 280 remained relatively undamaged. Low temperature preconditioning stimulated a 4-fold increase in catalase and peroxidase activities in fruit of NY280. High-temperature preconditioning appeared only to benefit fruit of NY280. Regardless of pretreatment, no significant change in superoxide dismutase activities were observed for either cultivar. These findings suggest that the ability to acclimate to low temperature stress may correlate with increased levels of catalase and peroxidase.

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Wenting He, Weiming Guo, and Zhongchun Jiang*

Effects of two pretreatments, i.e., ultrasonic wave (UW) and ultrasonic wave plus preservative solution (UW+PS), on water conditions of flower stem and membrane stability of petals in Nymphaea tetragona during 6-d cold wet storage. Compared with no pretreatment control, the two pretreatments prolonged the vase life and improved water conditions of the cut flower during cold storage to different degrees. Fresh weight of flower stems and relative water content of petals increased during cold storage. The water utilization efficiency of flower stem and water potential in different parts of flower stem were improved significantly as a result of the pretreatments. Although both pretreatments helped the cut flowers maintain favorable water relations, the effects of UW + PS combined pretreatment were better than UW pretreatment alone. In addition, UW and UW+PS inhibited the increase in the contents of lipid peroxidation product malondialdehyde (MDA) and superoxide anion in petals. UW + PS promoted superoxide dismutase (SOD) and catalase (CAT) activities in petals during cold storage to a greater degree than did UW.

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Shiow Y. Wang, Kim S. Lewers, Linda Bowman, and Min Ding

these reactive oxygen species or free radicals can cause oxidative damage to lipids, proteins, and nucleic acids, and thus promote cell death ( Morel and Dangl, 1997 ; Satué-Gracia et al., 1997 ). Physiological defenses against oxidative stress involve

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

.5%, v/v) was used as surfactant. Three days after beginning NaCl treatment, the fully expanded third leaves and the middle part of roots were harvested, immediately frozen in liquid nitrogen, and stored at –80 °C until required for analyzing free radical

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Haiyan Zhao, Haiying Liang, Yibing Chu, Congcong Sun, Ning Wei, Mengnan Yang, and Caixia Zheng

.2% to 0.6% NaCl decreased the scavenging rate on DPPH free radicals, whereas greater concentrations did not have an effect ( Fig. 4H ). In comparison, 0.2% and 0.4% NaCl decreased the scavenging rate on the hydroxyl radical in 64 d, but 0.6% and 0

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Zhong-Hua Bian, Rui-Feng Cheng, Qi-Chang Yang, Jun Wang, and Chungui Lu

-VIS spectrophotometer (UV-180) at 765 nm against water as a blank. The total phenolic compounds were calculated using a calibration curve with gallic acid as a standard. Measurement of DPPH free-radical scavenging activity. The free-radical scavenging capacity of the

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Samson Zeray Tesfay, Sakhile Mathe, Albert T. Modi, and Tafadzwanashe Mabhaudhi

. Gebicki, J. Puhl, H. Jürgens, G. 1992 The role of lipid peroxidation and antioxidants in oxidative modification of LDL Free Radic. Biol. Med. 13 341 390 Foyer, C.F. Nector, G. 2000 Oxygen processing in photosynthesis regulation and signaling New Phytol

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Ji-Lian Zheng, Lan-Ying Hu, Kang-Di Hu, Jun Wu, Feng Yang, and Hua Zhang

by various physiological and biochemical changes, including oxidative damage caused by reactive oxygen species (ROS) such as superoxide radicals (•O 2 – ) and H 2 O 2 ( Raseetha et al., 2013 ). ROS is highly reactive and causes lipid peroxidation