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Barbara Demmigadams - One of the best experts on this subject based on the ideXlab platform.
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linking the Xanthophyll Cycle with thermal energy dissipation
Photosynthesis Research, 2003Co-Authors: Barbara DemmigadamsAbstract:This perspective summarizes my personal recollections about the initial discovery of the involvement of the Xanthophyll Cycle in photoprotective energy dissipation, starting with my arrival at Olle Bjorkman’s laboratory at the Carnegie Institution and focusing on events from the mid-1980s to the early 1990s.
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ecophysiology of the Xanthophyll Cycle
1999Co-Authors: Barbara Demmigadams, William W Adams, Volker Ebbert, Barry A LoganAbstract:This chapter seeks to illustrate the impressive range of environmental modulation of the Xanthophyll Cycle in terrestrial plants in their natural habitats, where the demand for thermal energy dissipation can change within seconds or between seasons and vary from a moderate to a very large fraction of the absorbed light. Plants from habitats with concomitant Xanthophyll Cycle conversions and changes in energy dissipation activity are included as well as examples from habitats in which zeaxanthin and antheraxanthin (Z+A) persist and energy dissipation is modulated largely via their rapid engagement and disengagement. The well-characterized, rapidly inducible and reversible form of Xanthophyll Cycle-dependent energy dissipation is contrasted with the sustained maintenance of higher levels of (Z+A)-dependent thermal dissipation under various environmental stresses with an emphasis on seasonally low temperatures. Furthermore, the association of Z+A retention with the phenomenon of photoinhibition of Photosystem II (and alterations in the stoichiometry of proteins associated with PS II) is discussed as well as a possible involvement of thylakoid protein phosphorylation in sustained (Z+A)-dependent energy dissipation. An integrative understanding is sought by comparing acclimation patterns of thermal energy dissipation as well as overall foliar antioxidant capacity with those of photosynthetic and respiratory metabolism of whole plants. It is proposed that acclimation of all of these processes responds to whole plant source-sink relationships.
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antioxidants and Xanthophyll Cycle dependent energy dissipation in cucurbita pepo l and vinca major l acclimated to four growth ppfds in the field
Journal of Experimental Botany, 1998Co-Authors: Barry A Logan, Barbara Demmigadams, William W Adams, Stephen C GraceAbstract:The acclimation of photochemistry, Xanthophyll Cycle-dependent energy dissipation, and antioxidants was characterized in leaves of Cucurbita pepo L. and Vinca major L. that developed under photosynthetic photon flux densities (PPFDs) ranging from deep shade to full sunlight in the field. The predominant acclimatory response of leaf pigment composition was an increase in the Xanthophyll Cycle pool size with increasing growth PPFD. In both species, the estimated rate of thermal energy dissipation at midday increased with increasing PPFD and midday levels of zeaxanthin and antheraxanthin per chlorophyll were closely correlated with the levels of non-photochemical fluorescence quenching under all growth PPFD regimes. However, at full sunlight there appeared to be considerably higher levels of Xanthophyll Cycle-dependent energy dissipation in V. major compared with pumpkin while estimated rates of photochemistry exhibited the reverse trend. Leaf activities of the antioxidant enzymes ascorbate peroxidase and superoxide dismutase, as well as ascorbate content, increased with increasing growth PPFD in both plant species. Activities/contents were higher under 100% full sunlight and increased more strongly from intermediate growth PPFDs to 100% full sunlight in V. major than in C. pepo. These patterns of acclimation are similar to those exhibited by Xanthophyll Cycle-dependent energy dissipation. The patterns of acclimation of glutathione reductase are discussed in the context of the multiple roles for reduced glutathione. Catalase acclimated in a manner consistent with its role in scavenging H 2 O 2 generated via photorespiration and/or mitochondrial respiration. Leaf α-tocopherol did not exhibit growth PPFD-dependent trends.
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seasonal differences in Xanthophyll Cycle characteristics and antioxidants in mahonia repens growing in different light environments
Oecologia, 1998Co-Authors: Barry A Logan, William W Adams, Stephen C Grace, Barbara DemmigadamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-dependent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a single-layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipation in PSII and an increased capacity to detoxify reactive reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydroascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photosynthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded populations, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxygen species responded to the level of excess light absorption.
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enhanced employment of the Xanthophyll Cycle and thermal energy dissipation in spinach exposed to high light and n stress
Plant Physiology, 1997Co-Authors: Amy S Verhoeven, Barbara Demmigadams, William W AdamsAbstract:The involvement of the Xanthophyll Cycle in photoprotection of N-deficient spinach (Spinacia oleracea L. cv Nobel) was investigated. Spinach plants were fertilized with 14 mM nitrate (control, high N) versus 0.5 mM (low N) fertilizer, and grown under both high- and low-light conditions. Plants were characterized from measurements of photosynthetic oxygen exchange and chlorophyll fluorescence, as well as carotenoid and cholorophyll analysis. Compared with the high-N plants, the low-N plants showed a lower capacity for photosynthesis and a lower chlorophyll content, as well as a lower rate of photosystem II photosynthetic electron transport and a corresponding increase in thermal energy dissipation activity measured as nonphotochemical fluorescence quenching. The low-N plants displayed a greater fraction of the total Xanthophyll Cycle pool as zeaxanthin and antheraxanthin at midday, and an increase in the ratio of Xanthophyll Cycle pigments to total chlorophyll. These results indicate that under N limitation both the light-collecting system and the photosynthetic rate decrease. However, the increased dissipation of excess energy shows that there is excess light absorbed at midday. We conclude that spinach responds to N limitation by a combination of decreased light collection and increased thermal dissipation involving the Xanthophyll Cycle.
William W Adams - One of the best experts on this subject based on the ideXlab platform.
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ecophysiology of the Xanthophyll Cycle
1999Co-Authors: Barbara Demmigadams, William W Adams, Volker Ebbert, Barry A LoganAbstract:This chapter seeks to illustrate the impressive range of environmental modulation of the Xanthophyll Cycle in terrestrial plants in their natural habitats, where the demand for thermal energy dissipation can change within seconds or between seasons and vary from a moderate to a very large fraction of the absorbed light. Plants from habitats with concomitant Xanthophyll Cycle conversions and changes in energy dissipation activity are included as well as examples from habitats in which zeaxanthin and antheraxanthin (Z+A) persist and energy dissipation is modulated largely via their rapid engagement and disengagement. The well-characterized, rapidly inducible and reversible form of Xanthophyll Cycle-dependent energy dissipation is contrasted with the sustained maintenance of higher levels of (Z+A)-dependent thermal dissipation under various environmental stresses with an emphasis on seasonally low temperatures. Furthermore, the association of Z+A retention with the phenomenon of photoinhibition of Photosystem II (and alterations in the stoichiometry of proteins associated with PS II) is discussed as well as a possible involvement of thylakoid protein phosphorylation in sustained (Z+A)-dependent energy dissipation. An integrative understanding is sought by comparing acclimation patterns of thermal energy dissipation as well as overall foliar antioxidant capacity with those of photosynthetic and respiratory metabolism of whole plants. It is proposed that acclimation of all of these processes responds to whole plant source-sink relationships.
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antioxidants and Xanthophyll Cycle dependent energy dissipation in cucurbita pepo l and vinca major l acclimated to four growth ppfds in the field
Journal of Experimental Botany, 1998Co-Authors: Barry A Logan, Barbara Demmigadams, William W Adams, Stephen C GraceAbstract:The acclimation of photochemistry, Xanthophyll Cycle-dependent energy dissipation, and antioxidants was characterized in leaves of Cucurbita pepo L. and Vinca major L. that developed under photosynthetic photon flux densities (PPFDs) ranging from deep shade to full sunlight in the field. The predominant acclimatory response of leaf pigment composition was an increase in the Xanthophyll Cycle pool size with increasing growth PPFD. In both species, the estimated rate of thermal energy dissipation at midday increased with increasing PPFD and midday levels of zeaxanthin and antheraxanthin per chlorophyll were closely correlated with the levels of non-photochemical fluorescence quenching under all growth PPFD regimes. However, at full sunlight there appeared to be considerably higher levels of Xanthophyll Cycle-dependent energy dissipation in V. major compared with pumpkin while estimated rates of photochemistry exhibited the reverse trend. Leaf activities of the antioxidant enzymes ascorbate peroxidase and superoxide dismutase, as well as ascorbate content, increased with increasing growth PPFD in both plant species. Activities/contents were higher under 100% full sunlight and increased more strongly from intermediate growth PPFDs to 100% full sunlight in V. major than in C. pepo. These patterns of acclimation are similar to those exhibited by Xanthophyll Cycle-dependent energy dissipation. The patterns of acclimation of glutathione reductase are discussed in the context of the multiple roles for reduced glutathione. Catalase acclimated in a manner consistent with its role in scavenging H 2 O 2 generated via photorespiration and/or mitochondrial respiration. Leaf α-tocopherol did not exhibit growth PPFD-dependent trends.
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seasonal differences in Xanthophyll Cycle characteristics and antioxidants in mahonia repens growing in different light environments
Oecologia, 1998Co-Authors: Barry A Logan, William W Adams, Stephen C Grace, Barbara DemmigadamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-dependent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a single-layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipation in PSII and an increased capacity to detoxify reactive reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydroascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photosynthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded populations, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxygen species responded to the level of excess light absorption.
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Seasonal differences in Xanthophyll Cycle characteristics and antioxidants in Mahonia repens growing
1998Co-Authors: Barry A Logan, William W Adams, Stephen C. Grace William, Barbara Demmig-adamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-depen- dent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Moun- tains in deep shade, full exposure, and under a single- layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipa- tion in PSII and an increased capacity to detoxify re- active reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydro- ascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photo- synthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded popula- tions, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxy- gen species responded to the level of excess light absorption.
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The response of Xanthophyll Cycle-dependent energy dissipation in Alocasia brisbanensis to sunflecks in a subtropical rainforest
Australian Journal of Plant Physiology, 1997Co-Authors: D H Barker, William W Adams, Barry A Logan, Barbara Demmig-adamsAbstract:The photosynthetic responses of leaves of Alocasia brisbanensis (F.M. Bailey) Domin (Araceae) to sunflecks were monitored via chlorophyll fluorescence beneath the canopy of a subtropical rainforest in Australia. Additionally, the size and conversion state of the Xanthophyll Cycle were determined. Acclimation to understory environments that regularly experienced sunflecks involved small increases in the size of the Xanthophyll Cycle pool in comparison to understory plants that never received sunflecks. In understory plants that regularly experienced sunflecks the rate of photochemistry and the level of Xanthophyll Cycle-dependent energy dissipation closely tracked changes in incident PFD. Subsequent to the first sunfleck plants tended to retain their pool of Xanthophyll Cycle carotenoids as the deepoxidised forms (antheraxanthin and zeaxanthin) throughout the day. Retention of these deepoxidised forms apparently allows the trans-thylakoid membrane proton gradient to engage and disengage dissipation rapidly in response to a sunfleck, thereby mitigating photooxidative damage and ensuring a rapid return to efficient light utilisation via photosynthesis in limiting light. Our results were also in agreement with previous studies that demonstrated a requirement for light activation of photosynthesis.
Amy S Verhoeven - One of the best experts on this subject based on the ideXlab platform.
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seasonal changes in leaf antioxidant systems and Xanthophyll Cycle characteristics in taxus x media growing in sun and shade environments
Physiologia Plantarum, 2005Co-Authors: Amy S Verhoeven, Annie Swanberg, Mai Thao, John P WhitemanAbstract:We examined differences between summer and winter in Xanthophyll Cycle-dependent energy dissipation and leaf antioxidant systems in needles of the overwintering evergreen Taxus x media cv. Tauntonii (Taunton yew) growing in both sun and shade environments in Saint Paul, Minnesota. During the winter, both sun and shade plants exhibited increases in the capacity for, and utilization of, Xanthophyll Cycle-dependent thermal energy dissipation. Winter needles showed decreases (sun needles) or no change (shade needles) in superoxide dismutase activity (EC 1.15.1.1), no change in ascorbate peroxidase activity (EC 1.11.1.11) and no change (sun needles) or increases (shade needles) in reduced ascorbate levels. Both sun and shade needles showed large increases in glutathione reductase activity (EC 1.6.4.2) and total glutathione levels during the winter, in addition to increases in levels of a-tocopherol. These results suggest an important photoprotective role during the winter for Xanthophyll Cycle-dependent energy dissipation and for the antioxidants glutathione and a-tocopherol. They suggest a less important photoprotective function of the enzyme-based water–water Cycle in winter acclimation in the seasonally very cold environment of Minnesota.
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enhanced employment of the Xanthophyll Cycle and thermal energy dissipation in spinach exposed to high light and n stress
Plant Physiology, 1997Co-Authors: Amy S Verhoeven, Barbara Demmigadams, William W AdamsAbstract:The involvement of the Xanthophyll Cycle in photoprotection of N-deficient spinach (Spinacia oleracea L. cv Nobel) was investigated. Spinach plants were fertilized with 14 mM nitrate (control, high N) versus 0.5 mM (low N) fertilizer, and grown under both high- and low-light conditions. Plants were characterized from measurements of photosynthetic oxygen exchange and chlorophyll fluorescence, as well as carotenoid and cholorophyll analysis. Compared with the high-N plants, the low-N plants showed a lower capacity for photosynthesis and a lower chlorophyll content, as well as a lower rate of photosystem II photosynthetic electron transport and a corresponding increase in thermal energy dissipation activity measured as nonphotochemical fluorescence quenching. The low-N plants displayed a greater fraction of the total Xanthophyll Cycle pool as zeaxanthin and antheraxanthin at midday, and an increase in the ratio of Xanthophyll Cycle pigments to total chlorophyll. These results indicate that under N limitation both the light-collecting system and the photosynthetic rate decrease. However, the increased dissipation of excess energy shows that there is excess light absorbed at midday. We conclude that spinach responds to N limitation by a combination of decreased light collection and increased thermal dissipation involving the Xanthophyll Cycle.
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Close relationship between the state of the Xanthophyll Cycle pigments and photosystem II efficiency during recovery from winter stress
Physiologia Plantarum, 1996Co-Authors: Amy S Verhoeven, William W Adams, Barbara Demmig-adamsAbstract:The potential involvement of the Xanthophyll Cycle in photoprotection of overwintering evergreen plants was investigated. Leaves from five evergreen species, Pseudotsuga menziesii, Pinus ponderosa, Euonymus kiautschovicus, Mahonia repens and Malva neglecta, were collected from the field predawn during winter and transferred to the laboratory where chlorophyll fluorescence emission as well as the chlorophyll and carotenoid composition were ascertained periodically for 4.5 days. Leaves and needles from all species were found to have retained large amounts of the Xanthophyll Cycle pigments zeaxanthin and antheraxanthin, and they exhibited sustained low values of the intrinsic efficiency of photosystem II (PSII; measured as the ratio of variable to maximal fluorescence, F v /F m ) upon collection. The increase in PSII efficiency was biphasic, with a rapid phase (requiring several hours) and a slow phase (requiring several days). Changes in the conversion state of the Xanthophyll Cycle were found to correlate with increases in PSII efficiency in both phases, with the latter phase involving large increases in both F m (maximal fluorescence) and F o (minimal fluorescence) throughout the period of recovery. The relationship between F m quenching (expressed as nonphotochemical or Stern-Volmer quenching [NPQ] of F m , i.e. F m /F m ' -1) and F o quenching (F o F o '-1) was linear, as expected for changes in Xanthophyll Cycle-dependent energy dissipation in the antenna complexes. Furthermore, the relationship between F v /F m and NPQ during recovery followed the theoretical relationship predicted for changes in the rate constant for energy dissipation in the antenna complexes. This fit between the theoretical relationship and the actual data indicates that all changes in NPQ or F v /F m can be accounted for by changes in this rate constant. The results suggest a role for the photoprotective Xanthophyll Cycle-dependent dissipation process in the lowered efficiency of PSII observed in cold-stressed evergreen plants in the field.
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photoinhibition during winter stress involvement of sustained Xanthophyll Cycle dependent energy dissipation
Australian Journal of Plant Physiology, 1995Co-Authors: W Iii W Adams, Amy S Verhoeven, Barbara Demmigadams, D H BarkerAbstract:Sustained decreases in intrinsic photosystem II efficiency (i.e. Fv/Fm) in response to high light and chilling temperatures were examined in eight species, and were found to be accompanied by the retention of zeaxanthin (Z) and antheraxanthin (A) overnight. The quantitative relationship between changes in Fv/Fm and the A + Z level during these sustained changes on cold days was similar to that obtained for rapidly reversible changes on warm days. Furthermore, upon removal of leaves from the field, recovery from 'photoinhibition' (the reversal of the depression of Fv/Fm) matched the timecourse of the epoxidation of Z and A to violaxanthin (V). These findings suggest that the 'photoinhibition' occuring in these species might be due to the sustained engagement of these de-epoxidised components of the Xanthophyll Cycle in photoprotective energy dissipation. When examined over the course of several days during the winter, the predawn conversion state of the Xanthophyll Cycle responded to the daily changes in minimum air (and leaf) temperature, such that the Xanthophyll Cycle was largely de-epoxidised prior to sunrise on cold nights and was present predominantly as V after nights when the nocturnal temperatures were above freezing. In addition, in some of the species examined, there was a large acclimation of the Xanthophyll Cycle pool size to the level of excessive light, with a much larger pool present in the leaves examined during the winter and that pool being de-epoxidised to Z and A to a much greater degree at midday than from similar leaves examined during the summer. The Xanthophyll Cycle, and the photoprotective energy dissipation process associated with it, would thus appear to provide plants the flexibility required to deal with the excessive levels of light absorbed by chlorophyll under a wide range of climatic conditions, and can quite possibly account for the 'photoinhibition' observed during winter stress.
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Xanthophyll Cycle dependent energy dissipation and flexible photosystem ii efficiency in plants acclimated to light stress
Australian Journal of Plant Physiology, 1995Co-Authors: Barbara Demmigadams, Barry A Logan, W Iii W Adams, Amy S VerhoevenAbstract:The effect of an acclimation to light stress during the growth of leaves on their response to high photon flux densities (PFDs) was characterised by quantifying changes in photosystem II (PSII) characteristics and carotenoid composition. During brief experimental exposures to high PFDs sun leaves exhibited: (a) much higher levels of antheraxanthin + zeaxanthin than shade leaves, (b) a greater extent of energy dissipation in the light-harvesting antennae, and (c) a greater decrease of intrinsic PSII efficiency that was rapidly reversible. During longer experimental exposures to high PFD, deep-shade leaves but not the sun leaves showed slowly developing secondary decreases in intrinsic PSII efficiency. Recovery of these secondary responses was also slow and inhibited by lincomycin, an inhibitor of chloroplast-encoded protein synthesis. In contrast, under field conditions all changes in intrinsic PSII efficiency in open sun-exposed habitats as well as understory sites with intense sunflecks appeared to be caused by Xanthophyll Cycle-dependent energy dissipation. Furthermore, comparison of leaves with different maximal rates of electron transport revealed that all leaves compensated fully for these differences by dissipating very different amounts of absorbed light via Xanthophyll Cycle-dependent energy dissipation, thereby all maintaining a similarly low PSII reduction state. It is our conclusion that an increased capacity for Xanthophyll Cycle-dependent energy dissipation is a key component of the acclimation of leaves to a variety of different forms of light stress, and that the response of leaves to excess light experienced in the growth environment is thus likely to be qualitatively different from that to sudden experimental exposures to PFDs exceeding the growth PFD.
Barry A Logan - One of the best experts on this subject based on the ideXlab platform.
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Xanthophyll Cycle activity in two prominent arctic shrub species
Arctic Antarctic and Alpine Research, 2017Co-Authors: Troy S Magney, Barry A Logan, Jaret S Reblin, N Boelman, Jan U H Eitel, Heather E Greaves, Kevin L GriffinAbstract:ABSTRACT When the capacity for photosynthesis is constrained by unfavorable growing conditions, excess absorbed light is safely lost from leaves via thermal energy dissipation—a photoprotective mechanism ubiquitous among higher plants. The relatively low irradiance conditions yet stressful growing environment of the arctic tundra suggest contrasting hypotheses regarding the necessity for plant investment in photoprotection. To examine these hypotheses, the photoprotective pigments of the Xanthophyll Cycle were investigated in conjunction with non-photochemical quenching (NPQ) of chlorophyll fluorescence emission in two dominant arctic shrub species, Salix pulchra and Betula nana. The Xanthophyll Cycle pool sizes of S. pulchra leaves were substantially higher than those reported in most other higher plant species, whereas B. nana leaves maintain modestly high Xanthophyll Cycle pool sizes. In addition, high retention of de-epoxidized Xanthophyll Cycle pigments in both species and saturation of Xanthophyll c...
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ecophysiology of the Xanthophyll Cycle
1999Co-Authors: Barbara Demmigadams, William W Adams, Volker Ebbert, Barry A LoganAbstract:This chapter seeks to illustrate the impressive range of environmental modulation of the Xanthophyll Cycle in terrestrial plants in their natural habitats, where the demand for thermal energy dissipation can change within seconds or between seasons and vary from a moderate to a very large fraction of the absorbed light. Plants from habitats with concomitant Xanthophyll Cycle conversions and changes in energy dissipation activity are included as well as examples from habitats in which zeaxanthin and antheraxanthin (Z+A) persist and energy dissipation is modulated largely via their rapid engagement and disengagement. The well-characterized, rapidly inducible and reversible form of Xanthophyll Cycle-dependent energy dissipation is contrasted with the sustained maintenance of higher levels of (Z+A)-dependent thermal dissipation under various environmental stresses with an emphasis on seasonally low temperatures. Furthermore, the association of Z+A retention with the phenomenon of photoinhibition of Photosystem II (and alterations in the stoichiometry of proteins associated with PS II) is discussed as well as a possible involvement of thylakoid protein phosphorylation in sustained (Z+A)-dependent energy dissipation. An integrative understanding is sought by comparing acclimation patterns of thermal energy dissipation as well as overall foliar antioxidant capacity with those of photosynthetic and respiratory metabolism of whole plants. It is proposed that acclimation of all of these processes responds to whole plant source-sink relationships.
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antioxidants and Xanthophyll Cycle dependent energy dissipation in cucurbita pepo l and vinca major l acclimated to four growth ppfds in the field
Journal of Experimental Botany, 1998Co-Authors: Barry A Logan, Barbara Demmigadams, William W Adams, Stephen C GraceAbstract:The acclimation of photochemistry, Xanthophyll Cycle-dependent energy dissipation, and antioxidants was characterized in leaves of Cucurbita pepo L. and Vinca major L. that developed under photosynthetic photon flux densities (PPFDs) ranging from deep shade to full sunlight in the field. The predominant acclimatory response of leaf pigment composition was an increase in the Xanthophyll Cycle pool size with increasing growth PPFD. In both species, the estimated rate of thermal energy dissipation at midday increased with increasing PPFD and midday levels of zeaxanthin and antheraxanthin per chlorophyll were closely correlated with the levels of non-photochemical fluorescence quenching under all growth PPFD regimes. However, at full sunlight there appeared to be considerably higher levels of Xanthophyll Cycle-dependent energy dissipation in V. major compared with pumpkin while estimated rates of photochemistry exhibited the reverse trend. Leaf activities of the antioxidant enzymes ascorbate peroxidase and superoxide dismutase, as well as ascorbate content, increased with increasing growth PPFD in both plant species. Activities/contents were higher under 100% full sunlight and increased more strongly from intermediate growth PPFDs to 100% full sunlight in V. major than in C. pepo. These patterns of acclimation are similar to those exhibited by Xanthophyll Cycle-dependent energy dissipation. The patterns of acclimation of glutathione reductase are discussed in the context of the multiple roles for reduced glutathione. Catalase acclimated in a manner consistent with its role in scavenging H 2 O 2 generated via photorespiration and/or mitochondrial respiration. Leaf α-tocopherol did not exhibit growth PPFD-dependent trends.
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seasonal differences in Xanthophyll Cycle characteristics and antioxidants in mahonia repens growing in different light environments
Oecologia, 1998Co-Authors: Barry A Logan, William W Adams, Stephen C Grace, Barbara DemmigadamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-dependent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a single-layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipation in PSII and an increased capacity to detoxify reactive reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydroascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photosynthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded populations, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxygen species responded to the level of excess light absorption.
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Seasonal differences in Xanthophyll Cycle characteristics and antioxidants in Mahonia repens growing
1998Co-Authors: Barry A Logan, William W Adams, Stephen C. Grace William, Barbara Demmig-adamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-depen- dent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Moun- tains in deep shade, full exposure, and under a single- layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipa- tion in PSII and an increased capacity to detoxify re- active reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydro- ascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photo- synthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded popula- tions, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxy- gen species responded to the level of excess light absorption.
Barbara Demmig-adams - One of the best experts on this subject based on the ideXlab platform.
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Seasonal differences in Xanthophyll Cycle characteristics and antioxidants in Mahonia repens growing
1998Co-Authors: Barry A Logan, William W Adams, Stephen C. Grace William, Barbara Demmig-adamsAbstract:We investigated differences between summer and winter in photosynthesis, Xanthophyll Cycle-depen- dent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Moun- tains in deep shade, full exposure, and under a single- layered canopy of Pinus ponderosa (partially shaded). In summer, increasing growth irradiance (from deep shade to partial shade to full exposure) was associated with increased Xanthophyll Cycle-dependent energy dissipa- tion in PSII and an increased capacity to detoxify re- active reduced oxygen species, as measured by increases in the activities of ascorbate peroxidase, superoxide scavenging, glutathione reductase, and monodehydro- ascorbate reductase, as well as increases in leaf ascorbate and glutathione content. Leaves of exposed and partially shaded plants exhibited decreased capacities for photo- synthetic O2 evolution in winter compared to summer, while in the deeply shaded plants this parameter did not differ seasonally. Seasonal differences in the levels of antioxidants generally exhibited an inverse response to photosynthesis, being higher in winter compared to summer in the exposed and partially shaded popula- tions, but remaining unchanged in the deeply shaded population. In addition, total pool size and conversion state of the Xanthophyll Cycle were higher in winter than in summer in all populations. These trends suggest that both Xanthophyll Cycle-dependent energy dissipation in PSII and the capacity to detoxify reactive reduced oxy- gen species responded to the level of excess light absorption.
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The response of Xanthophyll Cycle-dependent energy dissipation in Alocasia brisbanensis to sunflecks in a subtropical rainforest
Australian Journal of Plant Physiology, 1997Co-Authors: D H Barker, William W Adams, Barry A Logan, Barbara Demmig-adamsAbstract:The photosynthetic responses of leaves of Alocasia brisbanensis (F.M. Bailey) Domin (Araceae) to sunflecks were monitored via chlorophyll fluorescence beneath the canopy of a subtropical rainforest in Australia. Additionally, the size and conversion state of the Xanthophyll Cycle were determined. Acclimation to understory environments that regularly experienced sunflecks involved small increases in the size of the Xanthophyll Cycle pool in comparison to understory plants that never received sunflecks. In understory plants that regularly experienced sunflecks the rate of photochemistry and the level of Xanthophyll Cycle-dependent energy dissipation closely tracked changes in incident PFD. Subsequent to the first sunfleck plants tended to retain their pool of Xanthophyll Cycle carotenoids as the deepoxidised forms (antheraxanthin and zeaxanthin) throughout the day. Retention of these deepoxidised forms apparently allows the trans-thylakoid membrane proton gradient to engage and disengage dissipation rapidly in response to a sunfleck, thereby mitigating photooxidative damage and ensuring a rapid return to efficient light utilisation via photosynthesis in limiting light. Our results were also in agreement with previous studies that demonstrated a requirement for light activation of photosynthesis.
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Close relationship between the state of the Xanthophyll Cycle pigments and photosystem II efficiency during recovery from winter stress
Physiologia Plantarum, 1996Co-Authors: Amy S Verhoeven, William W Adams, Barbara Demmig-adamsAbstract:The potential involvement of the Xanthophyll Cycle in photoprotection of overwintering evergreen plants was investigated. Leaves from five evergreen species, Pseudotsuga menziesii, Pinus ponderosa, Euonymus kiautschovicus, Mahonia repens and Malva neglecta, were collected from the field predawn during winter and transferred to the laboratory where chlorophyll fluorescence emission as well as the chlorophyll and carotenoid composition were ascertained periodically for 4.5 days. Leaves and needles from all species were found to have retained large amounts of the Xanthophyll Cycle pigments zeaxanthin and antheraxanthin, and they exhibited sustained low values of the intrinsic efficiency of photosystem II (PSII; measured as the ratio of variable to maximal fluorescence, F v /F m ) upon collection. The increase in PSII efficiency was biphasic, with a rapid phase (requiring several hours) and a slow phase (requiring several days). Changes in the conversion state of the Xanthophyll Cycle were found to correlate with increases in PSII efficiency in both phases, with the latter phase involving large increases in both F m (maximal fluorescence) and F o (minimal fluorescence) throughout the period of recovery. The relationship between F m quenching (expressed as nonphotochemical or Stern-Volmer quenching [NPQ] of F m , i.e. F m /F m ' -1) and F o quenching (F o F o '-1) was linear, as expected for changes in Xanthophyll Cycle-dependent energy dissipation in the antenna complexes. Furthermore, the relationship between F v /F m and NPQ during recovery followed the theoretical relationship predicted for changes in the rate constant for energy dissipation in the antenna complexes. This fit between the theoretical relationship and the actual data indicates that all changes in NPQ or F v /F m can be accounted for by changes in this rate constant. The results suggest a role for the photoprotective Xanthophyll Cycle-dependent dissipation process in the lowered efficiency of PSII observed in cold-stressed evergreen plants in the field.
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The Xanthophyll Cycle, Protein Turnover, and the High Light Tolerance of Sun-Acclimated Leaves.
Plant Physiology, 1993Co-Authors: Barbara Demmig-adams, William W AdamsAbstract:Changes in photosynthesis rate and photochemical characteristics in response to high irradiance, followed by recovery at low irradiance, were determined in four groups of sun-acclimated leaves of spinach (Spinacia oleracea L.). These four groups were untreated control leaves, leaves treated with either an inhibitor of energy dissipation associated with the Xanthophyll Cycle (dithiothreitol, DTT) or an inhibitor of chloroplast-encoded protein synthesis (chloramphenicol, CAP), as well as leaves treated with a combination of DTT + CAP. In these sun leaves, treatment with either CAP or DTT alone did not result in an inhibition of the recovery from high-light-induced decreases in photochemical efficiency. Only the treatment with a combination of CAP + DTT caused a strong and irreversible depression of photochemical efficiency. We suggest that in the presence of DTT (and in the absence of Xanthophyll Cycle-associated energy dissipation), protein turnover may be involved in the recovery process. We further suggest that the reversible depression of photochemical efficiency in CAP-treated sun leaves reflects Xanthophyll Cycle-associated energy dissipation. In the leaves treated with CAP + DTT a slowly developing decrease in the maximal yield of chlorophyll fluorescence in high light may indicate an alternative, Xanthophyll Cycle-independent dissipation process in the photochemical system. Moreover, CAP treatments did not cause any changes in the deepoxidation state of the Xanthophyll Cycle. However, CAP-treated leaves, but not those treated with CAP + DTT, exhibited some decrease in the pool size of the Xanthophyll Cycle during the exposure to high light.
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Operation of the Xanthophyll Cycle in higher plants in response to diurnal changes in incident sunlight
Planta, 1992Co-Authors: William W Adams, Barbara Demmig-adamsAbstract:Changes in the carotenoid composition of leaves in response to diurnal changes in sunlight were determined in the crop species Helianthus annuus L. (sunflower), Cucurbita pepo L. (pumpkin), and Cucumls sativus L. (cucumber), in the diaheliotropic mesophyte Malva neglecta Wallr., and in the perennial shrub Euonymus kiautschovicus Loesner. Large daily changes were observed in the relative proportions of the components of the Xanthophyll Cycle, violaxanthin (V), antheraxanthin (A), and zeaxanthin (Z) in plants grown in full sunlight. In all leaves large amounts of Z were formed at peak irradiance, with the changes in Z content closely following changes in incident photon flux density (PFD) over the course of the day. All leaves also contained large total pools of the three Xanthophyll-Cycle components. However, the extent to which the V pool present at dawn became de-epoxidized during the day varied widely among leaves, from a 27% decrease in M. neglecta to a 90% decrease in E. kiautschovicus . The largest amounts of Z and the lowest amounts of V at peak irradiance (full sunlight) were observed in the species with the lower rates of photosynthesis (particularly in E. kiautschovicus and pumpkin), and smaller amounts of Z and a lesser decrease in V content were found at peak irradiance in those species with the higher rates of photosynthesis (particularly in M. neglecta and sunflower). In all species some Z was present in the leaves prior to sunrise. Furthermore, in individuals of sunflower, pumpkin, and cucumber grown at 85% of full sunlight and transferred to full sunlight, a further increase in the already large pool of the Xanthophyll-Cycle pigments occurred over the course of 1 d.
