Quantum Yields of Photosystem II and Photosynthesis in an Aurea Mutant of Tobacco (C<sub>3</sub>) and an Oil Yellow Mutant of Maize (C<sub>4</sub>) Which Have High Capacities for Photosynthesis Despite Low Chlorophyll Contents

The quantum yields of non-cyclic electron transport from photosystem II (determined from chlorophyll a fluorescence) and carbon dioxide assimilation were measured in vivo in representative species of the three subgroups of C4 plants (NADP-malic enzyme, NAD-malic enzyme and PEP-carboxykinase) over a series of intercellular CO2 concentrations (CI) at both 21% and 2% O2. The CO2 assimilation rate was independent of O2 concentration over the entire range of Ci (up to 500 μbar) in all three C4 subgroups. The quantum yield of PS II electron transport was similar, or only slightly greater, in 21% v. 2% O2 at all Ci values. In contrast, in the C3 species wheat there was a large O2 dependent increase in PS II quantum yield at low CO2, which reflects a high level of photorespiration. In the C4 plants, the relationship of the quantum yield of PS II electron transport to the quantum yield of CO2 fixation is linear suggesting that photochemical use of energy absorbed by PS II is tightly linked to CO2 fixation in C4 plants. This relationship is nearly identical in all three subgroups and may allow estimates of photosynthetic rates of C4 plants based on measurements of PS II photochemical efficiency. The results suggest that in C4 plants both the photoreduction of O2 and photorespiration are low, even at very limiting CO2 concentrations.

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Effects of Cadmium Stress on Alternative Oxidase and Photosystem II in Three Wheat Cultivars

Zeitschrift für Naturforschung C ◽

10.1515/znc-2010-1-215 ◽

2010 ◽

Vol 65 (1-2) ◽

pp. 87-94 ◽

Cited By ~ 6

Author(s):

Yong-Ping Duan ◽

Shu Yuan ◽

Shi-Hua Tu ◽

Wen-Qiang Feng ◽

Fei Xu ◽

...

Keyword(s):

Photosystem Ii ◽

Alternative Oxidase ◽

Thiobarbituric Acid ◽

Cadmium Stress ◽

Wheat Cultivars ◽

Cd Stress ◽

Western Blots ◽

Chlorophyll Contents ◽

Water Contents ◽

Cyanide Resistant Respiration

The effects of Cd stress (200 μmol/L, 8 days) on respiration and photosynthesis of three wheat cultivars were investigated: Chuanyu 12 (CY12), Chuanmai 42 (CM42), and Chuanmai 47 (CM47). Fifteen-day-old seedlings were exposed to 200 μmol/L CdCl2 for 4 days and 8 days, respectively. The results indicated that Cd was accumulated largely in roots, but little in leaves of all three cultivars. CY12 accumulated the highest level of Cd in roots and showed the weakest resistance. On the contrary, the other two cultivars, CM42 and CM47, adapted better to Cd stress, and their thiobarbituric acid-reactive substances (TBARS) contents were lower than in CY12, but the chlorophyll contents and water contents were higher than in CY12. Additionally, Cd stress prompted the alternative oxidase (AOX) activity and upregulated the cyanide-resistant respiration in CM42 and CM47 after 8 days; no such induction was observed for CY12. The CO2 assimilation rate, leaf stomatal conductance and chlorophyll fl uorescence were inhibited by Cd stress in all cultivars, but more severe in the CY12 cultivar. Western blots indicated that the content of the photosystem II proteins LHCII and D1 decreased in CY12, but did not change in CM42 and CM47. While the content of the mitochondrial AOX protein increased markedly in CM42 and CM47, it did not in CY12. These results suggested that AOX and LHCII could be regarded as indicators of plant’s resistance to heavy metals.

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Quantum Yield of Photosystem II and Efficiency of CO2 Fixation in Flaveria (Asteraceae) Species under Varying Light and CO2

Functional Plant Biology ◽

10.1071/pp9910369 ◽

1991 ◽

Vol 18 (4) ◽

pp. 369 ◽

Cited By ~ 14

Author(s):

JP Krall ◽

GE Edwards ◽

MSB Ku

Keyword(s):

Quantum Yield ◽

Photosystem Ii ◽

Co2 Fixation ◽

C4 Photosynthesis ◽

Co2 Assimilation ◽

Quantum Yields ◽

Progressive Development ◽

Psii Activity ◽

C3 And C4 Photosynthesis

The quantum yields of electron transport from photosystem II (PSII) (Φe, determined from chlorophyll a fluorescence), and CO2 assimilation (ΦCO2, photosynthetic rate/light intensity) were measured simultaneously in vivo with representative species of Flaveria which show a progression in development between C3 and C4 photosynthesis and in reduction of photorespiration. These were F. pringlei (C3), F. sonorensis (C3-C4, but lacking a C4 cycle), F. floridana (C3-C4, with partially functional C4 cycle), F. brownii (C4-like) and F. bidentis (C4). The level of PSII activity with varying CI under 210 mbar O2 was very similar in all species. However, the progressive development of C4 characteristics among the species produced an increased efficiency in utilisation of PSII derived energy for CO2 assimilation under 210 mbar O2, due to reduced photorespiratory losses at low CO2 levels. In all species, when photorespiration was limited by low O2 (20 mbar), there was a linear or near linear relationship between the quantum yield of PSII v. the quantum yield of CO2 fixation with varying intercellular levels of CO2 (Ci) indicating that CO2 fixation in this case is linked to PSII activity. When switching from 20 to 210 mbar O2 at atmosphere levels of CO2, there was a similar decrease in the efficiency in utilising PSII activity for CO2 assimilation at different light intensities, but the degree of sensitivity to O2 progressively decreased among the species concomitant with the development of C4 photosynthesis. These results may help explain why there is an advantage to evolution of C4 photosynthesis in environments where Ci becomes limiting.

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PHOTOSYSTEM II QUANTUM YIELDS AND XANTHOPHYLL-CYCLE PIGMENTS OF THE MACROALGA SARGASSUM NATANS (PHAEOPHYCEAE): RESPONSES UNDER NATURAL SUNLIGHT

Journal of Phycology ◽

10.1046/j.1529-8817.1998.340104.x ◽

1998 ◽

Vol 34 (1) ◽

pp. 104-112 ◽

Cited By ~ 34

Author(s):

Oscar Schofield ◽

Terence J. Evens ◽

David F. Millie

Keyword(s):

Photosystem Ii ◽

Xanthophyll Cycle ◽

Quantum Yields ◽

Xanthophyll Cycle Pigments ◽

Natural Sunlight

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CHROMATIC REGULATION OF QUANTUM YIELDS FOR PHOTOSYSTEM II CHARGE SEPARATION, OXYGEN EVOLUTION, AND CARBON FIXATION IN HETEROCAPSA PYGMAEA (PYRROPHYTA)1

Journal of Phycology ◽

10.1111/j.1529-8817.1993.tb00146.x ◽

1993 ◽

Vol 29 (4) ◽

pp. 453-462 ◽

Cited By ~ 37

Author(s):

Bernd Kroon ◽

Barbara B. Prézelin ◽

Oscar Schofield

Keyword(s):

Photosystem Ii ◽

Oxygen Evolution ◽

Charge Separation ◽

Carbon Fixation ◽

Quantum Yields ◽

Heterocapsa Pygmaea

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Evaluation of Copper Oxide Nanoparticles Toxicity Using Chlorophyll a Fluorescence Imaging in Lemna gibba

Journal of Botany ◽

10.1155/2010/763142 ◽

2010 ◽

Vol 2010 ◽

pp. 1-9 ◽

Cited By ~ 28

Author(s):

François Perreault ◽

Abdallah Oukarroum ◽

Laura Pirastru ◽

Louka Sirois ◽

William Gerson Matias ◽

...

Keyword(s):

Photosystem Ii ◽

Copper Oxide ◽

Fluorescence Imaging ◽

Copper Oxide Nanoparticles ◽

Quantum Yields ◽

Lemna Gibba ◽

Photochemical Quenching ◽

Oxide Nanoparticles ◽

Photosynthetic Parameters ◽

Cuo Nps

Copper oxide nanoparticles (CuO NPs), used in antifouling paints of boats, are released in the environment and can induce toxicity to aquatic organisms. In this report, we used chlorophyll a fluorescence imaging to evaluate CuO NPs toxicity in Lemna gibba. This approach allowed to evaluate the differential effect of CuO NPs on photosynthesis of whole L. gibba plants. Exposure to 0.1 to 0.4 g/L CuO NPs during 48h induced strong inhibition of photosynthetic processes resulting in a decrease of plant growth. By using fluorescence imaging, different photosynthetic parameters were evaluated simultaneously in microplate conditions. Imaging of FO fluorescence yield showed the decrease of leaf photosynthetic active surface for whole plants exposed to CuO NPs. This method showed that CuO NPs inhibited photosystem II maximal, photosystem II operational quantum yields, and photochemical quenching of fluorescence associated with electron transport. Nonphotochemical fluorescence quenching as an indicator of energy dissipation not used in photosynthesis was shown to be increased by the effect of CuO NPs. Such approach in microplate conditions provides synchronous high repetition measurements for numerous plants. This study may give a reliable methodological approach to evaluate toxicity risk of NPs in aquatic ecosystems.

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