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  • 1
    Electronic Resource
    Electronic Resource
    Thylakoid-bound and stromal antioxidative enzymes in wheat treated with excess copper (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 104 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Copper is a catalyst in the formation of reactive free radicals and its toxicity may be due, at least in part, to oxidative damage. The response of thylakoid-bound and stromal antioxidative enzymes against the generation of superoxide radical was investigated in seedlings of wheat (Triticum durum L. cv. Adamello) grown in hydroponic culture for 10 days and subjected to 10 and 50 µM copper treatments. Electron spin resonance of roots evidenced a spectrum of copper, the intensity of which increased with the treatment, whereas the carbon-centered free radical spectrum detected in the control leaves was not seen anymore in the treated samples. As well as thylakoids, photosystem II (PSII) particles were able to produce the superoxide radical. Increased superoxide production both by thylakoids and PSII was observed in the sample treated with 50 µM Cu. Induction of thylakoid-bound and stromal antioxidative enzymes, with the exception of dehydroascorbate reductase, was also detected in leaves treated with the highest copper concentration. No Mn-superoxide dismutase (SOD, EC 1.15.1.1) was detected in thylakoids of wheat. Both stromal and thylakoid-bound SOD were CuZn-SOD with 16.2-kDa subunits. Both western blotting and immuno-electron microscopy showed that the SOD subunit was recognized by a polyclonal antibody against glyoxisomal CuZn-SOD from watermelon cotyledon. In the stroma of wheat, ascorbate peroxidase showed at least three well-resolved bands differently induced by copper treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040416.x
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  • 2
    Electronic Resource
    Electronic Resource
    Some effects of cadmium on maize plants (1993)
    Springer
    Archives of environmental contamination and toxicology 25 (1993), S. 244-249 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The growth of the whole plant and the chlorophyll content, oxygen evolution, and chloroplast ultrastructure of leaf tissues have been studied in maize plants grown on a culture medium either without cadmium (Cd) or supplied with increasing concentrations of the metal. The plants treated with high Cd concentrations showed symptoms of heavy metal toxicity, such as length reduction of both roots and shoots, leaf bleaching, ultrastructural alterations of chloroplasts and lowering of photosynthetic activity. Some symptoms appeared at 100 μM Cd, but the strong toxic effects of the metal were found only at 250 μM Cd.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00212136
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological and ultrastructural aspects of dehydration and rehydration in leaves of Sporobolus stapfianus (1998)
    Springer
    Plant growth regulation 24 (1998), S. 219-228 
    Details
    ISSN: 1573-5087
    Keywords: Sporobolus stapfianus ; resurrection plant ; desiccation-tolerance ; leaf morphology ; leaf ultrastructure ; leaf dehydration/rehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The resurrection species Sporobolus stapfianus Gandoger has been studied by LM, TEM and SEM in order to define the leaf morphology and fine structure and to analyse the cellular changes occurring during the processes of dehydration and rehydration of the plant. Some characteristics of the fully hydrated leaf and some ultrastructural and physiological events which take place during leaf wilting are discussed in relation to their possible role in plant desiccation-tolerance. The leaves of S. stapfianus show several characteristics common among xerophytic species. In the resurrection leaf they could play a role in slowing down the drying rate, thus leaving time to activate the mechanisms protecting the cell structures against drought damage. Actually, the S. stapfianus leaves do not undergo important cellular alterations during dehydration. The chloroplasts, in particular, retain part of their photosynthetic pigments and thylakoid membranes. Upon rewatering leaf recovery is rather fast and the tissue structure and cell organization of the fully hydrated state are already regained after two days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005853527769
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  • 4
    Electronic Resource
    Electronic Resource
    Cab gene expression in bleached leaves of carotenoid-deficient maize (2000)
    Springer
    Photosynthesis research 64 (2000), S. 119-126 
    Details
    ISSN: 1573-5079
    Keywords: amitrole ; bleaching herbicides ; Cab gene expression ; carotenoid-deficient mutants ; chloroplast photodamage ; norflurazon ; ultrastructure ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The chloroplast photo-oxidation and the expression of the Cab gene Lhcb1, encoding the Lhcb1 light-harvesting chlorophyll a/b-protein of PS II, have been studied in leaf cells of maize treated with the two bleaching herbicides norflurazon and amitrole and of the two carotenoid-free mutants vp9 and vp2 grown under high photodamaging light. Both herbicides and mutations caused severe photo-oxidation of organelles. However, the plastids of norflurazon-treated and vp2 leaves were totally devoid of thylakoids and did not contain any chlorophyll, while the organelles of amitrole-treated and vp9 leaves still had a few altered and photosynthetically unfunctional membranes and very small quantities of chlorophylls. Despite the dramatic photodamage undergone by the plastids over several days, the cells of amitrole-treated and vp9 leaves maintained a certain expression of the Lhcb1 gene which, on the contrary, was completely blocked in the cells of norflurazon-treated and vp2 leaves. The experimental results, obtained by integrating biochemical and molecular analyses with ultrastructural observations, show that the maintainance of Cab gene expression does not strictly depend on intact and functional chloroplasts. The transcription of these genes, still maintained in cells with greatly photo-oxidized organelles, seems to be inversely related to the degree of thylakoid demolition, which can affect the last steps of chlorophyll biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006477215572
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  • 5
    Electronic Resource
    Electronic Resource
    An ultrastructural study of maize leaf etioplasts throughout their entire life-cycle (1986)
    Springer
    Protoplasma 130 (1986), S. 98-107 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays L. ; Etioplasts ; Etioplast differentiation ; Etioplast senescence ; Optical diffraction ; Prolamellar body arrangement ; Prothylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The entire life-cycle of maize leaf etioplasts has been followed. Prolamellar bodies with different types of tubular membrane arrangement can be found in the juvenile stages of the organelles, while in mature etioplasts nearly all the prolamellar bodies exhibit an “hexagonal ring” arrangement, which, by optical diffraction, appears to be the most regular and compact possible. The prothylakoid membranes also undergo changes during organelle differentiation, and their different organization and arrangement produce a clear dimorphism between the etioplasts of mesophyll and bundle sheath cells. In senescent etioplasts the prothylakoids are more affected, while the prolamellar bodies appear rather stable, also in situations where protochlorophyll(ide) content is very low. The formation of clusters of osmiophilic globules is coupled with the breakdown of the etioplast membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276591
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  • 6
    Electronic Resource
    Electronic Resource
    Intrathylakoidal crystal appearance during the vital cycle of spinach chloroplasts (1985)
    Springer
    Protoplasma 126 (1985), S. 153-157 
    Details
    ISSN: 1615-6102
    Keywords: Spinacia oleracea L. ; Chloroplast ontogenesis ; Chloroplast senescence ; Spinach chloroplasts ; Intrathylakoidal crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The entire vital cycle of chloroplasts was followed in spinach leaves, in order to determine the plastidial situations leading to the build-up of intrathylakoidal crystals. This kind of inclusion was noticed in the juvenile ontogenetic stages as well as in the senescent chloroplast stage, while intrathylakoidal crystals were not present in the mature organelles. The appearance of such crystals, which are known to consist of ribulose 1,5-diphosphate carboxylase, is interpreted as a consequence of an imbalance between enzyme level and membrane function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01287682
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