Radical Production and Scavenging in the Chloroplasts

Asada, Kozi

doi:10.1007/0-306-48135-9_5

Cited by 184 publications

(195 citation statements)

References 118 publications

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“…AOS are generated by a range of reductive metabolic activities including, most notably, respiration, photosynthesis and N # fixation (Dalton, 1995). In addition to its ability to react directly with AOS, ASC also provides the reductant for the enzymic scavenging of H # O # by ASC peroxidase, a universal enzyme in chloroplasts as well as the cytoplasm of plant cells (Asada, 1996). *Author for correspondence (fax j1 503 777 7773 ; e-mail david.dalton!reed.edu).…”

Section: mentioning

confidence: 99%

Effects of exogenous application and stem infusion of ascorbate on soybean (Glycine max) root nodules

Bashor

Dalton

1999

New Phytologist

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Numerous biochemical and physiological studies have demonstrated the importance of ascorbate (ASC) as a reducing agent and antioxidant in higher plant metabolism. Of special note is the capacity of ASC to eliminate damaging activated oxygen species (AOS) including O # d and H # O # . N # -fixing legume nodules are especially vulnerable to oxidative damage because they contain large amounts of leghaemoglobin which produces AOS through spontaneous autoxidation ; thus, ASC and other components of the ascorbate-reduced glutathione (ASC-GSH) pathway are critical antioxidants in nodules. In order to establish a meaningful correlation between concentrations of ASC and capacity for N # fixation in legume root nodules, soybean (Glycine max) plants were treated with excess ASC via exogenous irrigation or continuous intravascular infusion through needles inserted directly into plant stems. Treatment with ASC led to striking increases in nitrogenase activity (acetylene reduction), nodule leghaemoglobin content, and activity of ASC peroxidase, a key antioxidant enzyme. The concentration of lipid peroxides, which are indicators of oxidative damage and onset of senescence, was decreased in ASC-treated nodules. These results support the conclusion that ASC is critical for N # fixation and that elevated ASC allows nodules to maintain a greater capacity to fix N # over longer periods.

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Section: mentioning

confidence: 99%

Effects of exogenous application and stem infusion of ascorbate on soybean (Glycine max) root nodules

Bashor

Dalton

1999

New Phytologist

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“…Although superoxide itself may be damaging under some circumstances, it may cause greater harm by leading to the formation of the highly reactive hydroxyl radical from H 2 O 2 , the product of superoxide dismutation in the chloroplast (Bowler et al 1992). In addition, singlet O 2 , another unstable ROS, can be formed via resonance energy transfer from triplet excited-state chlorophyll to ground-state O 2 (Asada 1996;Niyogi 1999). ROS-mediated inactivation is thought to be one of the primary causes of the slowly reversible loss of photosynthetic activity commonly termed 'photoinhibition,' which is sometimes observed in leaves exposed to light in combination with environmental stresses (Allen 1995;Niyogi 1999).…”

Section: Introductionmentioning

confidence: 99%

The role of antioxidant enzymes in photoprotection

et al. 2006

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The enzymatic component of the antioxidant system is discussed as one of the defensive mechanisms providing protection against excessive light absorption in plants. We present an analysis of attempts to improve stress tolerance by means of the creation of transgenic plants with elevated antioxidant enzyme activities and conclude that the effect of such transgenic manipulation strongly depends on the manner in which the stress is imposed. The following factors may diminish the differences in photosynthetic performance between transgenic plants and wild type under field conditions: effective functioning of the thermal dissipation mechanisms providing a primary line of defense against excessive light, long-term adjustments of the antioxidant system and other photoprotective mechanisms, the relatively low level of control over electron transport exerted by the Water-Water cycle, especially under warm conditions, and a decrease in the content of the transgenic product during leaf aging.

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“…photosynthetically active photon flux density: RWC, relative water content; cf>pSn, relative quantum efficiency of pho tosystem II photochemistry; ip, water potential. photoreduction of oxygen occurs, especially under severe drought conditions, resulting in the forma tion of activated oxygen species such as singlet ox ygen, superoxide radical and lipid peroxides, which can lead to photodamage, chlorophyll de gradation, and lipid peroxidation (Smirnoff, 1993;Foyer et al, 1994;Asada, 1996;Osmond et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

α-Tocopherol Protection Against Drought-Induced Damage In Rosmarinus Officinalis L. And Melissa Officinalis L.

Munné‐Bosch

Schwarz²,

Alegre³

1999

Zeitschrift Für Naturforschung C

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a-Tocopherol, Photosynthesis, Drought, Rosmarinus officinalis, Melissa officinalis Summer diurnal variations of photosynthesis and a-tocopherol content were measured in relation to natural drought in field-grown rosemary (Rosmarinus officinalis L.) and lemon balm (Melissa officinalis L.) plants. During the summer relative water contents (RW C) of ca. 40% in Rosmarinus officinalis and ca. 30% in Melissa officinalis were attained, indicating severe drought. Both species showed similar diurnal patterns of net C 0 2 assimilation rates (A ) with a wide plateau of maximum photosynthesis at midday in the absence of drought and one peak of maximum photosynthesis early in the morning under drought conditions. Net C 0 2 assimilation rates decreased by ca. 75% due to drought in both species. Melissa officinalis plants showed a significant decrease in the relative quantum efficiency of PSII photochemistry (4>psn), ratio of variable to maximum fluorescence yield (F J F m) and chloro phyll content of leaves by ca. 25% under drought conditions at midday. In contrast, cJ)pSI1, F J F m and chlorophyll content remained constant throughout the experiment in R. officinalis plants. Although the non-photochemical quenching of chlorophyll fluorescence increased from ca. 1.8 to 3 and the a-tocopherol content rose fifteen fold in both species in response to drought, only R. officinalis plants were able to avoid oxidative damage under drought conditions by the joint increase of carotenoids and a-tocopherol.

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Radical Production and Scavenging in the Chloroplasts

Cited by 184 publications

References 118 publications

Effects of exogenous application and stem infusion of ascorbate on soybean (Glycine max) root nodules

Effects of exogenous application and stem infusion of ascorbate on soybean (Glycine max) root nodules

The role of antioxidant enzymes in photoprotection

α-Tocopherol Protection Against Drought-Induced Damage In Rosmarinus Officinalis L. And Melissa Officinalis L.

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