The effects of UV-B radiation on photosynthesis in relation to Photosystem II photochemistry, thermal dissipation and antioxidant defenses in winter wheat (Triticum aestivum L.) seedlings at different growth temperatures

2007 ◽  
Vol 34 (10) ◽  
pp. 907 ◽  
Author(s):  
Shu-Hua Yang ◽  
Li-Jun Wang ◽  
Shao-Hua Li ◽  
Wei Duan ◽  
Wayne Loescher ◽  
...  
Keyword(s):  
Low Temperature ◽  
Photosystem Ii ◽  
Winter Wheat ◽  
Antioxidant System ◽  
Xanthophyll Cycle ◽  
Thermal Dissipation ◽  
Antioxidant Defenses ◽  
Thiobarbituric Acid Reactive Substance ◽  
Xanthophyll Cycle Pigments ◽  
Psii Photochemistry

To study the UV-B effect on photosynthesis in winter wheat at different day/night temperatures, biologically effective UV-B radiation at 4.2 (LUVB) and 10.3 (HUVB) kJ m–2 d–1 was provided on the seedlings at 25/20°C or 10/5°C. UV-B radiation inhibited net photosynthesis rate (Pn) by enhanced intensity and decreased temperature without change of intercellular CO2 concentrations (Ci). Decreased maximal quantum yield of Photosystem II (Fv/Fm) and increased minimum fluorescence (Fo) were observed in HUVB at both temperatures and LUVB at 10/5°C. HUVB increased total pool size (VAZ) of xanthophyll cycle pigments, but decreased the de-epoxidation state (DEPS) of these pigments at both temperatures, while LUVB only decreased DEPS at 10/5°C. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and the redox states of ascorbate and glutathione (AsA/DAsA and GSH/GSSG) were enhanced at 25/20°C, while there were increased SOD and CAT, unaltered APX activities and AsA/DHA, as well as decreased GR activity and GSH/GSSG in LUVB and HUVB at 10/5°C. UV-B radiation resulted in higher H2O2 and thiobarbituric acid reactive substance (TBARS) concentrations at 10/5°C than 25/20°C. It appears that low temperature alone did not influence photosynthesis but aggravated UV-B induced photoinhibition, which was associated with PSII photochemistry rather than stomatal limitation. Xanthophyll cycle pigments failed to provide photoprotection through thermal dissipation. The antioxidant system was up-regulated in LUVB and HUVB at 25/20°C, but was impaired at 10/5°C. Low temperature intensified UV-B induced photoinhibition and damage by weakening the antioxidant system.

Xanthophyll cycle, light energy dissipation and photosystem II down-regulation in senescent leaves of wheat plants grown in the field

2001 ◽  
Vol 28 (10) ◽  
pp. 1023 ◽  
Author(s):  
Congming Lu ◽  
Qingtao Lu ◽  
Jianhua Zhang ◽  
Qide Zhang ◽  
Tingyun Kuang
Keyword(s):  
Energy Dissipation ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Xanthophyll Cycle ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Down Regulation ◽  
Psii Efficiency ◽  
Psii Photochemistry ◽  
Assimilation Capacity

Photosynthesis, the xanthophyll cycle, light energy dissipation and down-regulation of photosystem II (PSII) in senescent leaves of wheat plants grown in the field were investigated. With the progress of senescence, maximal efficiency of PSII photochemistry decreased only slightly early in the morning but substantially at midday. Actual PSII efficiency, photochemical quenching, efficiency of excitation capture by open PSII centres, and the I–P phase of fluorescence induction curves decreased significantly and such decreases were much more evident at midday than in the morning. At the same time, non-photochemical quenching, thermal dissipation and de-epoxidation status of the xanthophyll cycle increased, with much greater increases at midday than in the morning. These results suggest that the xanthophyll cycle played a role in photoprotection of PSII in senescent leaves by dissipating excess excitation energy. Taking into account the substantial decrease in photosynthetic capacity in senescent leaves, our data seem to support the view that the decrease in actual PSII efficiency in senescent leaves may represent a mechanism to down-regulate photosynthetic electron transport to match the decreased CO2 assimilation capacity and avoid photodamage of PSII from excess excitation energy.

scholarly journals Photoprotective Mechanisms of `Concord' Grape Leaves in Relation to Iron Supply

2005 ◽  
Vol 130 (3) ◽  
pp. 331-340 ◽  
Author(s):  
Brandon R. Smith ◽  
Lailiang Cheng
Keyword(s):  
Leaf Area ◽  
Antioxidant System ◽  
Xanthophyll Cycle ◽  
Thermal Dissipation ◽  
Fe Deficiency ◽  
Monodehydroascorbate Reductase ◽  
Fe Content ◽  
Area Basis ◽  
Antioxidant Metabolites ◽  
Β Carotene

The objective of this study was to quantify how photoprotective mechanisms in the leaves of `Concord' grapevines (Vitis labruscana Bailey) respond to a range of iron (Fe) supply. Own-rooted, 1-year-old container-grown vines were fertigated twice weekly for 11 weeks with a complete nutrient solution containing 1, 10, 20, 50, or 100 μm Fe from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA). Leaf total Fe content did not increase in response to Fe supply; however, “active” Fe (extracted with 2,2′-dipyridyl) and chlorophyll (Chl) increased on a leaf area basis as applied Fe increased. At the lowest active Fe level, leaf absorptance and the efficiency of excitation transfer (Fv′/Fm′) was lower, and nonphotochemical quenching (NPQ) was significantly greater. Photosystem II (PSII) quantum efficiency decreased curvilinearly, and the proportion of PSII reaction centers in the open state (qP) decreased linearly as active Fe content decreased. On a Chl basis, the xanthophyll cycle pool size [violaxanthin (V) + antheraxanthin (A) + zeaxanthin (Z)], lutein, and β-carotene increased curvilinearly as active Fe decreased, and neoxanthin (Neo) increased at the lowest Fe level. On a leaf area basis, as active Fe decreased, V+A+Z and β-carotene decreased curvilinearly, and lutein and Neo decreased linearly. At noon, conversion of V to A and Z increased as active Fe decreased. On a Chl basis, activities of antioxidant enzymes superoxide dismutase (SOD), monodehydroascorbate reductase (MDAR), and dehydroascorbate reductase (DHAR) increased curvilinearly, and glutathione reductase (GR) activity increased linearly as active Fe levels declined. Ascorbate peroxidase (APX) and catalase (CAT), on a Chl basis, were relatively constant. On a leaf area basis, a decrease in active Fe increased SOD and MDAR activity, whereas APX, CAT, DHAR and GR activity decreased. Antioxidant metabolites ascorbate (AsA), dehydroascorbate (DAsA), reduced glutathione (GSH) and oxidized glutathione (GSSG) also increased in response to Fe limitation when expressed on a Chl basis, whereas on a leaf area basis AsA and DAsA decreased and GSH increased curvilinearly. The GSH:GSSG ratio increased as active Fe declined, whereas the AsA:DAsA ratio did not change. In conclusion, both photoprotective mechanisms, xanthophyll cycle-dependent thermal dissipation and the ascorbate-glutathione antioxidant system, are enhanced in response to Fe deficiency to cope with excess absorbed light. In a low soil pH tolerant species such as V. labruscana, the foliar antioxidant system was upregulated in response to excess absorbed light from Fe deficiency-induced chlorosis, and there was no evidence of an increase in oxidative stress from high rates of applied Fe-EDDHA.

scholarly journals CO2 Assimilation, Carbohydrate Metabolism, Xanthophyll Cycle, and the Antioxidant System of `Honeycrisp' Apple Leaves with Zonal Chlorosis

2004 ◽  
Vol 129 (5) ◽  
pp. 729-737 ◽  
Author(s):  
Li-Song Chen ◽  
Lailiang Cheng
Keyword(s):  
Excitation Energy ◽  
Carbohydrate Metabolism ◽  
Antioxidant System ◽  
Xanthophyll Cycle ◽  
Calvin Cycle ◽  
Thermal Dissipation ◽  
Nonstructural Carbohydrates ◽  
Bisphosphate Carboxylase ◽  
Key Enzymes ◽  
Fructose 1,6 Bisphosphatase

To determine the cause of a characteristic zonal chlorosis of `Honeycrisp' apple (Malus ×domestica Borkh.) leaves, we compared CO2 assimilation, carbohydrate metabolism, the xanthophyll cycle and the antioxidant system between chlorotic leaves and normal leaves. Chlorotic leaves accumulated higher levels of nonstructural carbohydrates, particularly starch, sorbitol, sucrose, and fructose at both dusk and predawn, and no difference was found in total nonstructural carbohydrates between predawn and dusk. This indicates that carbon export was inhibited in chlorotic leaves. CO2 assimilation and the key enzymes in the Calvin cycle, ribulose 1,5-bisphosphate carboxylase/oxygenase, NADP-glyceraldehyde-3-phosphate dehydrogenase, phosphoribulokinase, stromal fructose-1,6-bisphosphatase, and the key enzymes in starch and sorbitol synthesis, ADP-glucose pyrophosphorylase, cytosolic fructose-1,6-bisphosphatase, and aldose 6-phosphate reductase were significantly lower in chlorotic leaves than in normal leaves. However, sucrose phosphate synthase activity was higher in chlorotic leaves. In response to a reduced demand for photosynthetic electron transport, thermal dissipation of excitation energy (measured as nonphotochemical quenching of chlorophyll fluorescence) was enhanced in chlorotic leaves under full sun, lowering the efficiency of excitation energy transfer to PSII reaction centers. This was accompanied by a corresponding increase in both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to antheraxanthin and zeaxanthin. The antioxidant system, including superoxide dismutase and ascorbate peroxidase and the ascorbate pool and glutathione pool, was up-regulated in chlorotic leaves in response to the increased generation of reactive oxygen species via photoreduction of oxygen. These findings support the hypothesis that phloem loading and/or transport is partially or completely blocked in chlorotic leaves, and that excessive accumulation of nonstructural carbohydrates may cause feedback suppression of CO2 assimilation via direct interference with chloroplast function and/or indirect repression of photosynthetic enzymes.

Long-term effects of temperature shifts on xanthophyll cycle and photoinhibition in spinach (Spinacia oleracea)

1999 ◽  
Vol 26 (2) ◽  
pp. 125 ◽  
Author(s):  
G. H. Krause ◽  
N. Carouge ◽  
H. Garden
Keyword(s):  
Low Temperature ◽  
Xanthophyll Cycle ◽  
Spinacia Oleracea ◽  
Temperature Shift ◽  
Long Term Effects ◽  
Xanthophyll Cycle Pigments ◽  
Spinacia Oleracea L ◽  
Autumn And Winter ◽  
Kinetics Of

The present study tested with spinach (Spinacia oleracea L.), whether leaves are capable of long-term acclimative responses of carotenoids when warm-grown (20°C) plants were subjected to a regime of low temperature (1–6°C) and excess light (250 mol m–2 s–1). About 17 days after the temperature shift, leaves of the third leaf pair were compared with the respective leaves of warm-grown control plants. The cold-treated leaves exhibited reduced susceptibility to photoinhibition (at 4°C) and considerably faster kinetics of ‘recovery’ (at 20°C), as determined by changes in the ratio of dark-adapted variable to maximum chlorophyll fluorescence, FV/FM. The temperature shift induced marked changes in the composition of photosynthetic pigments. In particular, the pool of xanthophyll cycle pigments, viola-, anthera- and zeaxanthin, based on chlorophyll a+b, was enlarged by about 50%. The proportion of xanthophyll cycle pigments referred to the sum of carotenoids increased by about 25% and, in excessive light, a larger fraction of violaxanthin became deepoxidized. Overall, in respect of carotenoid composition and xanthophyll cycle activity, leaves that had been acclimated by temperature shift were very similar to leaves acclimated by growth in the field during autumn and winter. The data show that in spinach leaves, photoprotective mechanisms can be induced by temperature shift without requirement for development and growth at low temperature.

scholarly journals CO2 Assimilation, Carbohydrate Metabolism, Xanthophyll Cycle, and the Antioxidant System of `Honeycrisp' Apple Leaves with Zonal Chlorosis

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 886E-887
Author(s):  
Li-Song Chen ◽  
Lailiang Cheng*
Keyword(s):  
Excitation Energy ◽  
Carbohydrate Metabolism ◽  
Antioxidant System ◽  
Xanthophyll Cycle ◽  
Calvin Cycle ◽  
Excitation Energy Transfer ◽  
Thermal Dissipation ◽  
Bisphosphate Carboxylase ◽  
Apple Leaves ◽  
Fructose 1,6 Bisphosphatase

To determine the cause of zonal chlorosis of `Honeycrisp' apple leaves, we compared CO2 assimilation, carbohydrate metabolism, xanthophyll cycle and the antioxidant system between chlorotic leaves and normal leaves. Chlorotic leaves accumulated higher levels of non-structural carbohydrates, particularly starch, sorbitol, sucrose, and fructose at both dusk and predawn, and no difference was found in total non-structural carbohydrates between predawn and dusk. CO2 assimilation and the key enzymes in the Calvin cycle, ribulose 1,5-bisphosphate carboxylase/oxygenase, NADP-glyceraldehyde-3-phosphate dehydrogenase, phosphoribulokinase, stromal fructose-1,6-bisphosphatase, and enzymes in starch and sorbitol synthesis, ADP-glucose pyrophosphorylase, cytosolic fructose-1,6-bisphosphatase, and aldose 6-phosphate reductase were significantly lower in chlorotic leaves than in normal leaves. However, sucrose phosphate synthase activity was higher in chlorotic leaves. Thermal dissipation of excitation energy was enhanced in chlorotic leaves under full sun, lowering the efficiency of excitation energy transfer to PSII reaction centers. This was accompanied by a corresponding increase in both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to antheraxanthin and zeaxanthin. The antioxidant system was up-regulated in chlorotic leaves in response to the increased generation of reactive oxygen species. These findings support the hypothesis that phloem loading and/or transport is partially or completely blocked in chlorotic leaves, and that excessive accumulation of non-structural carbohydrates may cause feedback suppression of CO2 assimilation via direct interference with chloroplast function and/or indirect repression of photosynthetic enzymes.

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