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    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this review we explore several models which might explain ozone (O3)-induced injury to plant foliage. Ozone enters the cell through the wall and plasma membrane where active oxygen species are generated. If the concentration of O3 is very high, unregulated cell death will occur. Alternatively, the active oxygen species, or succeeding reaction products, may serve as elicitors of regulated plant responses. These regulated responses include the induction of ethylene which could serve as a primary signal for—or a facilitator of—subsequent responses. The role of regulated suppression of photosynthetic genes and induction of chitinases and β-1,3-glucanase in programmed cell death is explored. Induction of antioxidants, enzymes of lignification and glutathione-S-transferase are discussed in the context of O3-induced cell repair or cell protection. A second model is postulated to explain induction of accelerated foliar senescence by low levels of O3. The notion that O3-induced elicitation of responses in the nucleus might lead to increased oxidative stress in the chloroplast is considered as a mechanism for accelerating the rate of degradation of ribulose-1,5-bisphosphate car-boxylase/oxygenase (Rubisco). The mechanisms by which O3 induces loss of Rubisco, and the relationship to accelerated foliar senescence are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 103 (1998), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The rate-limiting enzyme in the ethylene biosynthesis pathway is 1-aminocyclo-propane-1-carboxylate (ACC) synthase. We have investigated an ozone (O3)-induced ACC synthase gene in Arabidopsis thaliana. Four previously reported ACC synthase genes from A. thaliana (ACS1, ACS2, ACS4 and ACS5) were not induced in response to O3 stress. An O3-induced 1 098-bp cDNA encoding ACC synthase was isolated from foliage of A. thaliana; this sequence was identical to that of ACS6 which could be induced by multiple stimuli including touch. When plants were treated with 350 nl l−1 of O3 for 2 or 6 h. the evolution of ethylene became maximal after 1.5 h and gradually decreased thereafter. Similarly, the mRNA transcript of O3-induced ACC synthase was detected after 30 min of exposure, attained a maximum level after 1 h, and then declined. Visible damage in O3-treated plants was observed at the end of the 2-h exposure. This ACC synthase gene in A. thaliana provides a useful tool for studying O3-induced responses related to ethylene production at the molecular and genetic levels.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 62 (1984), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Brassinosteroid (BR) an analogue of brassinolide was tested in combination with thirteen 2,4-dichlorophenoxyacetic acid-L-amino acid conjugates for its possible synergistic effects on ethylene production by etiolated mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. When BR was used in combination with 2,4-D-L-amino acid conjugates the degree of enhanced ethylene production varied with the conjugate tested. In fact, the activity of the conjugate alone was directly related to its activity with BR.
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  • 6
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Brassinosteroid (BR) stimulation of auxin-induced ethylene production and the particular step at which BR acts to promote such synthesis were studied in mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. Increasing concentrations of methionine alone and in combination with 3 μM BR and 10 μM IAA had a minimal effect on ethylene production. With increasing concentrations of 1-aminocyclopro-pane-1-carboxylic acid (ACC), however, ethylene production increased. BR or IAA further enhanced ethylene production with maximum rates occurring when these compounds were added together with ACC. The addition of 10 μM CoCl2 in conjunction with BR and/or IAA resulted in 85–97% inhibition of ethylene production. When 20 μM cycloheximide was used in conjunction with BR and/or IAA there was a complete inhibition of ethylene production. Total inhibition also resulted when 1.0 μM aminoethoxy-vinylglycine (AVG) was used in combination with BR and/or IAA. AVG alone had no effect on ACC conversion to ethylene.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Brassinosteroid, an analogue of brassinolide, (BR) (2α, 3α, 22β, 23β-tetrahydroxy-24β-methyl-B-homo-7-oxa-5α-cholestan-6-one), was tested in conjunction with indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), indole-3-butyric acid (IBA), indole-3-propionic acid (IPA), indole-3-pyruvic acid (IPyA), indole-3-aldehyde (IAld), indole-3-carbinol (ICB) or tryptophan (TRP) for its effects on ethylene production by etiolated mung bean (Vigna radiata (L.) Rwilcz cv. Berken) hypocotyl segements. The enhancement of ethylene production due to BR was greatest in conjunction with 1 μM IBA, 2,4-D, IAA, or NAA (these increases were 2580, 2070, 890, and 300%, respectively). When increasing concentrations of IBA, 2,4-D, IAA, or NAA were used, there was a decrease in the percentage stimulation by BR. Both IPyA and IPA had different optimal concentrations than the other auxins tested. Their BR-enhanced maximum percentage stimulations (1430 and 1580%) were greatest with 5 μM IPya and 10 μM IPA, respectively. There was a marked reduction in the percentage stimulation by BR with either 100 μM IPyA or IPA. The inactive indoles (IAld, ICB, or TRP) did not synergize with BR at any of the concentrations tested. Four hours following treatment those segments in contact with 1 μM BR with or without the addition of 10 μM IAA began to show a stimulation in ethylene production above the control and this stimulation became greater over the following 20 h. It was necessary for BR to be in continual contact with the tissue to have a stimulatory effect on auxin-induced ethylene production. When segments excised from greater distances below the hypocotyl hook, were treated with either IAA alone or in combination with BR, there was a decrease in ethylene production with increasing distance. There was no effect of hypocotyl length on BR stimulation of auxin-induced ethylene production; however, there was a definite decrease in ethylene production when IAA was applied alone.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 65 (1985), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The inhibitory effects of aminooxyacetic acid (AOA) and cobalt chloride (CoCl2) on brassinosteroid (BR)-induced epinasty in tomato plants (Lycopersicon esculentum Mill. cv. Heinz 1350) are evaluated. CoCl2 dramatically decreases petiole bending and ethylene production as the concentration increases from 50 to 200 μM. The content of 1-aminocyclopropane-1-carboxylic acid (ACC) in the petiole, instead of accumulating, is reduced and does not change over the concentration range tested. Inhibition of BR-induced epinasty by AOA results from inhibition of ACC synthesis. There are dramatic reductions in petiole bending, ethylene and ACC production as the concentration of AOA is increased from 50 to 200 μM. Maximum inhibition occurs when the plants are pretreated with the inhibitors. The degree of inhibition increases as the length of pretreatment increases from 1 to 4 h. The response of BR-treated plants to AOA and CoCl2 is similar to the effect of auxin, indicating the integral relationship between BR and auxin.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 60 (1984), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three cytokinins and their ribosides were tested in conjunction with brassinosteroid (BR) for their effects on ethylene production in etiolated mung bean (Vigna radiata L. Rwilcz cv. Berken) hypocotyl segments. When varying concentrations of BR were tried in combination with a fixed amount of kinetin (10 μM), there was an increase in ethylene production with increasing concentrations of BR up to 3 μM, and a decline beyond. A stimulation in ethylene production was observed with increasing concentrations of each of the cytokinins used. However, when applied in conjunction with 3 μM BR, all cytokinin concentrations produced similar stimulatory patterns. When 3 μM BR or 10 μM 6-benzylaminopurine (BAP) was applied in conjunction with increasing concentrations of IAA, there was a stimulation in ethylene production with increasing concentrations of IAA. However, 3 μM BR and 10 μM BAP together with varying concentrations of IAA failed to alter the level of ethylene production.
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  • 10
    ISSN: 1573-5079
    Keywords: acclimation ; photosynthesis ; rbcL ; rbcS ; source strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous investigations have shown that increased source strength as a result of elevated CO2 can alter the timing of the phases of change that occur in photosynthetic rates during dicot leaf ontogeny [Miller et al. (1997) Plant Physiol 115: 1195–1200]. To evaluate the converse situation of decreased source strength, we examined leaf development in rbcS antisense mutants of tobacco. These mutants have depressed Rubisco levels and decreased rates of carbohydrate production. We found that antisense leaves are longer-lived than wild type leaves and that this appeared to be due to a prolongation of the senescence phase of development, as monitored by photosynthetic rates, chlorophyll content, and the abundance and activity of Rubisco. Declines in these parameters during leaf ontogeny in both the wild type and mutant plants were generally accompanied by coordinate reductions in the levels of rbcS mRNA and rbcL mRNA, as well as by reductions in chloroplast rRNA, chloroplast DNA and total protein. We suggest that the prolongation of senescence in the antisense leaves is due to an impact of source strength on leaf developmental programming that occurs, at least in part, at the level of transcript abundance of nuclear and chloroplast genes for chloroplast rRNAs and proteins. We hypothesize that plants are capable of sensing a range of source strength conditions to initiate and modulate leaf developmental programming.
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