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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced photochemical light utilization and decreased chilling-induced photoinhibition of photosystem II in cotton overexpressing genes encoding chloroplast-targeted antioxidant enzymes (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 113 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The aim of this study was to determine whether increases in stromal superoxide dismutase (SOD; EC 1.15.1.1), ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) via transformation could reduce photosystem (PS) II photoinhibition at low temperature for cotton (Gossypiumhirsutum L.) plants and to determine by what mechanism this protection may be realized. During 3-h exposures of lincomycin-treated leaf discs to 10°C and a photon flux density of 500 μmol m−2 s−1, all transgenic plants exhibited significantly greater PSII activity and O2 evolution than did wild-type plants. Also, the rate constant of PSII photoinactivation was significantly lower for all transgenic plants than for wild-type plants. No significant differences existed between genotypes in non-photochemical quenching of chlorophyll a fluorescence and the regulated component of the thermal dissipation of excitation energy. The relationship between changes in variable to maximum chlorophyll fluorescence (Fv/Fm) and the time-dependent averaged excessive light exposure was similar for all genotypes. This observation excluded the possibility that differences in PSII photodamage were due to improvements in the direct protection of PSII from active oxygen by antioxidant enzyme overproduction. Similar decreases in Fv/Fm during the stress treatment for all genotypes when leaves were pre-treated with 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) suggested that the effect of overproduction involved events downstream of PSII in the electron transfer pathway. Since all transgenic plants exhibited a significantly higher photochemical quenching of chlorophyll fluorescence during the chilling treatment, we concluded that, under the conditions used in this study, the enhancement of the protection of PSII from photodamage by increasing the stromal antioxidant enzyme activity in cotton leaves was due to the maintenance of a higher rate of electron transport and, consequently, a lower reduction state of QA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1130304.x
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  • 2
    Electronic Resource
    Electronic Resource
    C3−C4 Intermediate species in the genus Flaveria: leaf anatomy, ultrastructure, and the effect of O2 on the CO2 compensation concentration (1984)
    Springer
    Planta 160 (1984), S. 25-32 
    Details
    ISSN: 1432-2048
    Keywords: C3−C4 intermediate species ; Carbon dioxide compensation concentration ; Flaveria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf anatomical, ultrastructural, and CO2-exchange analyses of three closely related species of Flaveria indicate that they are C3−C4 intermediate plants. The leaf mesophyll of F. floridana J.R. Johnston, F. linearis Lag., and F. chloraefolia A. Gray is typical of that in dicotyledonous C3 plants, but the bundle sheath cells contain granal, starch-containing chloroplasts. In F. floridana and F. chloraefolia, the chloroplasts and numerous associated mitochondria are arranged largely centripetally, as in the closely related C4 species, F. brownii A.M. Powell. In F. linearis, fewer mitochondria are present and the chloroplasts are more evenly distributed throughout the bundle sheath cytosol. There is no correlation between the bundle sheath ultrastructure and CO2 compensation concentration. (Γ) values of these C3−C4 intermediate Flaveria species. At 21% O2 and 25°C, Γ for F. chloraefolia, F. linearis, and F. floridana is 23–26, 14–19, and 8–10 μl CO2 l-1, respectively. The O2 dependence of Γ is the greatest for F. chloraefolia and F. linearis (similar to that for C3−C4 intermediate Panicum and Moricandia species) and the least for F. floridana, whose O2 response is identical to that for F. brownii from 1.5 to 21% O2, but greater at higher pO2. The variation in leaf anatomy, bundle sheath ultrastructure, and O2 dependence of Γ among these Flaveria species may indicate an active evolution in the pathway of photosynthetic carbon metabolism within this genus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392462
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  • 3
    Electronic Resource
    Electronic Resource
    Differential expression of ribulose-1,5-bisphosphate carboxylase in reciprocal F1 hybrids of a C3 and a C4-likeFlaveria species (1989)
    Springer
    Biochemical genetics 27 (1989), S. 497-505 
    Details
    ISSN: 1573-4927
    Keywords: ribulose-1,5-bisphosphate carboxylase/oxygenase ; C3 ; C4 ; Flaveria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Stable reciprocal hybrids betweenFlaveria pringlei (C3) andF. brownii (C4-like) have been produced by standard breeding techniques. There are no differences in the isoelectric focusing patterns of the catalytic subunits of the ribulose-1,5-bisphosphate carboxylase/oxygenase fromF. pringlei, F. brownii, or the reciprocal hybrids. The enzyme from both species also contains an identical noncatalytic subunit polypeptide. However, the carboxylase enzyme fromF. brownii contains another isomeric form of noncatalytic subunit polypeptide which is resolveable by isoelectric focusing. This isomeric form constitutes about 50% of the total noncatalytic subunits in this species. It comprises only about 10% of the total noncatalytic subunit population in the C3×C4 plants, but about 42% of the noncatalytic subunits in the reciprocal cross. The concentrations of the holoenzyme in the reciprocal hybrids are comparable to those of the respective maternal parent. We hypothesize that a differential inheritance of parental chloroplasts by the reciprocal hybrids may be associated with this apparent maternal influence on the expression of the noncatalytic polypeptides and the holoenzyme concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553627
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  • 4
    Electronic Resource
    Electronic Resource
    Differential expression of ribulose-1,5-bisphosphate carboxylase in reciprocal F1 hybrids of a C3 and a C4-likeFlaveria species (1989)
    Springer
    Biochemical genetics 27 (1989), S. 497-505 
    Details
    ISSN: 1573-4927
    Keywords: ribulose-1,5-bisphosphate carboxylase/oxygenase ; C3 ; C4 ; Flaveria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Stable reciprocal hybrids betweenFlaveria pringlei (C3) andF. brownii (C4-like) have been produced by standard breeding techniques. There are no differences in the isoelectric focusing patterns of the catalytic subunits of the ribulose-1,5-bisphosphate carboxylase/oxygenase fromF. pringlei, F. brownii, or the reciprocal hybrids. The enzyme from both species also contains an identical noncatalytic subunit polypeptide. However, the carboxylase enzyme fromF. brownii contains another isomeric form of noncatalytic subunit polypeptide which is resolveable by isoelectric focusing. This isomeric form constitutes about 50% of the total noncatalytic subunits in this species. It comprises only about 10% of the total noncatalytic subunit population in the C3×C4 plants, but about 42% of the noncatalytic subunits in the reciprocal cross. The concentrations of the holoenzyme in the reciprocal hybrids are comparable to those of the respective maternal parent. We hypothesize that a differential inheritance of parental chloroplasts by the reciprocal hybrids may be associated with this apparent maternal influence on the expression of the noncatalytic polypeptides and the holoenzyme concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396147
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic/photorespiratory characteristics of C3−C4 intermediate species (1984)
    Springer
    Photosynthesis research 5 (1984), S. 307-323 
    Details
    ISSN: 1573-5079
    Keywords: C3−C4 ; intermediate ; photosynthesis ; photorespiration ; Panicum sp. ; Moricandia sp. ; Flaveria sp. ; Neurachne sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent of photorespiration, the inhibition of apparent photosynthesis (APS) by 21% O2, and the leaf anatomical and ultrastructural features of the naturally occurring C3−C4 intermediate species in the diverse Panicum, Moricandia, and Flaveria genera are between those features of representative C3 and C4 plants. The greatest differences between the photosynthetic/photorespiratory CO2 exchange characteristics of the C3−C4 intermediates and C3 plants occur for the parameters which are measured at low pCO2 (i.e., the CO2 compensation concentration and rates of CO2 evolution into CO2-free air in the light). The rates of APS by the intermediate species at atmospheric pCO2 are similar to those of C3 plants. The mechanisms which are responsible for reducing photorespiration in the C3−C4 intermediate species are poorly understood, but two proposals have been advanced. One emphasizes the importance of limited C4 photosynthesis which reduces O2 fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase, and, thus, reduces photorespiration by a CO2-concentrating mechanism, while the other emphasizes the importance of the internal recycling of photorespiratory CO2 evolved from the chloroplast/mitochondrion-containing bundle-sheath cells. There is no evidence from recent studies that limited C4 photosynthesis is responsible for reducing photorespiration in the intermediate Panicum and Moricandia species. However, preliminary results suggest that some, but not all, of the intermediate Flaveria species may possess a limited C4 cycle. The importance of a chlorophyllous bundle-sheath layer in the leaves of intermediate Panicum and Moricandia species in a mechanism based on the recycling of photorespiratory CO2 is uncertain. Therefore, although they have yet to be clearly delineated, different strategies appear to exist in the C3−C4 intermediate group to reduce photorespiration. Of major importance is the finding that some mechanism(s) other than Crassulacean acid metabolism or C4 photosynthesis has (have) evolved in at least the majority of these terrestrial intermediate species to reduce the seemingly wasteful metabolic process of photorespiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034976
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