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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 1.1.15.1.1) and peroxidase (POD: EC 1.11.1.7) 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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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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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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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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Shiow Y. Wang and Kim S. Lewers

harmful free radicals and have been associated with lower incidence and mortality rates of cancer and heart disease in addition to a number of other health benefits ( Ames et al., 1993 ; Dragsted et al., 1993 ; Velioglu et al., 1998 ; Wang et al., 1996

Open access

Yi Gong, Ronald B. Pegg, Adrian L. Kerrihard, Brad E. Lewis, and Richard J. Heerema

Pecan (Carya illinoinensis) is a tree nut native to North America. Although inhibited light exposure (most specifically as a result of overlapping tree canopies) has been shown to impair yield, the effect of this factor on nut antioxidant properties remains unknown. This study investigated effects of mechanical pruning and canopy height position of fruit on pecan kernel antioxidant contents and capacity. Beginning in 2006, trees in a ‘Western’ pecan orchard in New Mexico were subjected to three mechanical pruning frequency treatments (annual, biennial, and triennial) paralleling conventional practices, while other trees were maintained as unpruned controls. During the 2012 to 2014 seasons, pecans were sampled at fruit maturity from three canopy height zones (“low,” “middle,” and “high,” corresponding to 1.5 to 3.0 m, 3.0 to 4.5 m, and 4.5 to 6.0 m above the orchard floor). In vitro phenolics contents and antioxidant capacities of the nutmeats were evaluated by total phenolics content (TPC) and oxygen radical absorbance capacity (H-ORACFL), respectively. Soluble ester- and glycoside-bound phenolics were quantified by reversed-phase high-performance liquid chromatography (HPLC). For both TPC and H-ORACFL, results determined pruned samples had significantly higher values than unpruned samples (P < 0.001 for both comparisons), and that samples of “high” canopy height were significantly greater than those of “middle” height, which were in turn greater than those of “low” height (P < 0.001 for all comparisons). HPLC findings showed that in all three phenolic fractions (free, esterified, and glycoside-bound phenolics), nuts acquired from pruned trees had substantially greater concentrations of ellagic acid and its derivatives. Our findings indicate mechanical pruning of pecan trees and higher tree canopy position of fruit increase nut antioxidant properties.

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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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Li-Juan Zhang, Tian-Xiu Zhong, Li-Xin Xu, Lie-bao Han, and Xunzhong Zhang

Soil water deficit impacts cold acclimation and freezing tolerance in creeping bentgrass (Agrostis stolonifera L.), but the mechanisms underlying have not been well understood. The objectives of this study were to investigate the effects of deficit irrigation before and during cold acclimation on osmoprotectants, antioxidant metabolism, and freezing tolerance in creeping bentgrass. The grass was subjected to three-soil moisture levels: well-watered [100% container capacity (CC)], deficit irrigation induced-mild drought stress (60% CC), and severe drought stress (30% CC) for 35 days including 14 days at 24/20 °C (day/night) and then 21 days under cold acclimation treatment (2 °C) in growth chambers. Leaf proline and total soluble sugar (TSS) levels were higher in the grass under mild drought stress relative to that under severe drought stress. Superoxide (O2 −·), hydrogen peroxide (H2O2), and malondialdehyde (MDA) content were higher in the grass under severe drought relative to that under well-watered and mild drought stress at day 35. Mild drought stress increased catalase (CAT) and guaiacol peroxidase (POD) activity, induced new isoforms and increased band intensities of superoxide dismutase (SOD), CAT, and POD during cold acclimation (days 14 to 35). No differences in osmoprotectants, antioxidant metabolism, and freezing tolerance were found between mild drought and well-watered treatments. The results of this study suggest deficit irrigation-induced mild drought stress in late fall and winter could induce accumulation of osmoprotectants and improve antioxidant metabolism, and freezing tolerance, but severe drought stress could reduce freezing tolerance of creeping bentgrass in the region with limited precipitation.

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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