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  • 1
    Electronic Resource
    Electronic Resource
    Protection against the photo-induced inactivation of the photosystem II complex by abscisic acid (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To examine the effect of abscisic acid (ABA) on the photo-induced inactivation of the photosystem II (PSII) complex, a suspension culture of Chlamydomonas reinhardtii was treated with ABA for 24 h in darkness and then, after removal of ABA, the cells were exposed to strong light at a photon flux density of 2000 μmol m−2 s−1 at various temperatures. The activity of PSII, as estimated in terms of chlorophyll fluorescence and the evolution of oxygen, decreased significantly during the exposure of cells to the strong light, and the extent of the photo-induced decrease in PSII activity was much greater at lower temperatures. Irrespective of temperature, the decrease in PSII activity in ABA-treated cells was significantly smaller than that in control cells. Moreover, the recovery of PSII activity from the photo-inactivated state in ABA-treated cells was significantly faster than that in control cells. The recovery of PSII activity in both ABA-treated and control cells was almost entirely prevented by the presence of chloramphenicol. These results indicate that ABA protects the PSII complex in C. reinhardtii against photo-induced inactivation by accelerating the recovery of this complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00579.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regeneration of plants from callus cultures of Origanum vulgare L. (1992)
    Springer
    Plant cell reports 11 (1992), S. 476-479 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Investigations were undertaken to achieve rapid multiplication and improvement of Origanum vulgare (a herbaceous, ornamental plant well known for its aromatic and medicinal value) through plant regeneration from callus. The explants (cotyledons, hypocotyl and root segments) excised from 15 d old aseptic seedlings were cultured on Gamborg's B5 medium supplemented with 2,4-D, NAA and BAP individually and in various combinations (at concentrations of 0,10−7,10−6 and 10−5 M). Best callus induction was noted on medium with 10−7 M 2,4-D alone. The cotyledonary expiants proved to be the best source for compact and nodulated callus. The subcultured cotyledonary calli showed shoot induction when transferred onto media supplemented with BAP alone orin combination with 10−7M or 10−6MNAA. However, 10−5M NAA completely suppressed the shoot inducing ability of BAP. In general, NAA promoted root induction from all explants used including cotyledonary callus. Best shoot induction was obtained on medium supplemented with 10−6M BAP+10−6MNAA. Both IBA and NAA at 10−6 M proved to be equally effective in induction of roots from the cut ends of 15–20 mm long shoots (excised from callus) in half-strength B5 liquid medium. Rooted shoots were successfully re-established in soil under controlled conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232694
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  • 3
    Electronic Resource
    Electronic Resource
    Transformation of Brassica juncea (L.) Czern with bacterial codA gene enhances its tolerance to salt stress (2000)
    Springer
    Molecular breeding 6 (2000), S. 489-499 
    Details
    ISSN: 1572-9788
    Keywords: Choline oxidase ; glycinebetaine ; transformation ; Brassica juncea ; salt stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The codA gene for biosynthesis of glycinebetaine from Arthrobacter globiformis was used for transforming Brassica juncea cv. Pusa Jaikisan (which lack any means to synthesize glycinebetaine) through Agrobacterium mediated transformation. The stable insertion of the codA gene in the shoots obtained on medium with kanamycin and hygromycin was confirmed by PCR analysis of the nptII gene. Southern hybridization with a codA probe further demonstrated its successful integration. Immunoblot analysis revealed the presence of choline oxidase demonstrating that the bacterial codA gene had been successfully transcribed and translated. The seeds of transgenic lines showed enhanced capacity to germinate under salt stress as compared to that of the wild type. Further, the seedlings of transgenic plants that expressed codA gene showed significantly higher growth than that of the wild type under salt stress conditions. These results demonstrated that the introduction of a biosynthetic pathway for glycinebetaine into Brassica juncea significantly enhanced their salt tolerance. Hence, homozygous genotypes of selected transformed lines can be exploited for improving the salt tolerance of the desirable cultivars of Brassica juncea through breeding programmes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026542109965
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibition of mitochondrial electron transport is the prime cause behind proline accumulation during mineral deficiency in Oryza sativa (1993)
    Springer
    Plant and soil 155-156 (1993), S. 465-468 
    Details
    ISSN: 1573-5036
    Keywords: iron ; mineral deficiency ; mitochondrial electron transport ; NADH ; Oryza sativa ; proline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The concentration of proline in shoots of rice (Oryza sativa) seedlings raised in distilled water was about 3.3 times higher than in the seedlings raised in modified B5 medium. The shoots of seedlings raised in B5 medium which was depleted of calcium, iron, magnesium or potassium had a higher concentration of proline than those grown in standard B5 medium. The shoots of seedlings raised in distilled water with iron had a lower level of proline than those in distilled water. These results suggest that iron deficiency leads to high proline accumulation. The electron transport activity of mitochondria from shoots of etiolated seedlings raised in distilled water or iron-depleted B5 medium was significantly lower than those from equivalent seedlings raised with an iron source. As suppression in mitochondrial electron transport leads to an increase in NADH/NAD+ ratio, we propose that the prime cause of the proline accumulation during iron deficiency is to readily maintain NADH/NAD+ ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025084
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  • 5
    Electronic Resource
    Electronic Resource
    Enhanced tolerance to light stress of transgenic Arabidopsis plants that express the codA gene for a bacterial choline oxidase (1999)
    Springer
    Plant molecular biology 40 (1999), S. 279-288 
    Details
    ISSN: 1573-5028
    Keywords: choline oxidase ; codA gene ; photo-induced inactivation ; transformed Arabidopsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Arabidopsis thaliana was transformed with the codA gene from Arthrobacter globiformis. This gene encodes choline oxidase, an enzyme that converts choline to glycinebetaine. The photosynthetic activity, monitored in terms of chlorophyll fluorescence, of transformed plants was more tolerant to light stress than that of wild-type plants. This enhanced tolerance to light stress was caused by acceleration of the recovery of the photosystem II (PS II) complex from the photo-inactivated state. The transformed plants synthesized glycinebetaine, but no changes were detected in the relative levels of membrane lipids or in the relative levels of fatty acids in the various membrane lipids. Transformation with the codA gene increased levels of H2O2, a by-product of the reaction catalyzed by choline oxidase, by only 50% to 100% under stress or non-stress conditions. The activity of ascorbate peroxidase and, to a lesser extent, that of catalase in transformed plants were significantly higher than in the wild-type plants. These observations suggest that H2O2 produced by choline oxidase in the transformed plants might have stimulated the expression of H2O2 scavenging enzymes, with resultant maintenance of the level of H2O2 within a certain limited range. It appears that glycinebetaine produced in vivo, but not changes in membrane lipids or in the level of H2O2, protected the PS II complex in transformed plants from damage due to light stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006121821883
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  • 6
    Electronic Resource
    Electronic Resource
    Proline in relation to free radical production in seedlings of Brassica juncea raised under sodium chloride stress (1993)
    Springer
    Plant and soil 155-156 (1993), S. 497-500 
    Details
    ISSN: 1573-5036
    Keywords: Brassica juncea ; free radicals ; malondialdehyde ; proline ; sodium chloride stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The production of malondialdehyde (MDA) was higher in cotyledons from NaCl-raised Brassica juncea seedlings than in control seedlings. Light accelerated the MDA-producing capacity of thylakoids isolated from both control and treated seedlings. When exposed to strong white light (920 μmol photons m-2 s-1) the thylakoids from NaCl seedlings produced nearly 5 times more MDA than control thylakoids. In the cotyledons of NaCl seedlings, the proline level was 24-fold higher than in controls. The presence of proline during exposure of thylakoids to white light decreased MDA levels. The reduction in MDA production was higher in the thylakoids of NaCl seedlings than of controls. It is proposed that proline accumulation has an adaptive significance as it lowers the generation of free radicals and thus reduces the lipid peroxidation linked membrane deterioration under stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025092
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