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  • 1
    Electronic Resource
    Electronic Resource
    ISOPRENE EMISSION FROM PLANTS (2001)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 52 (2001), S. 407-436 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Very large amounts of isoprene are emitted from vegetation, especially from mosses, ferns, and trees. This hydrocarbon flux to the atmosphere, roughly equal to the flux of methane, has a large effect on the oxidizing potential of the atmosphere. Isoprene emission results from de novo synthesis by the deoxyxylulose phosphate/methyl erythritol 4-phosphate pathway in plastids. Dimethylallyl pyrophosphate made by this pathway is converted to isoprene by isoprene synthase. Isoprene synthase activity in plants has a high pH optimum and requirement for Mg2+ that is consistent with its location inside chloroplasts. Isoprene emission costs the plant significant amounts of carbon, ATP, and reducing power. Researchers hypothesize that plants benefit from isoprene emission because it helps photosynthesis recover from short high-temperature episodes. The evolution of isoprene emission may have been important in allowing plants to survive the rapid temperature changes that can occur in air because of the very low heat capacity of isoprene relative to water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.52.1.407
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photosynthesis is particularly sensitive to heat stress and recent results provide important new insights into the mechanisms by which moderate heat stress reduces photosynthetic capacity. Perhaps most surprising is that there is little or no damage to photosystem II as a result of moderate heat stress even though moderate heat stress can reduce the photosynthetic rate to near zero. Moderate heat stress can stimulate dark reduction of plastoquinone and cyclic electron flow in the light. In addition, moderate heat stress may increase thylakoid leakiness. At the same time, rubisco deactivates at moderately high temperature. Relationships between effects of moderate heat on rubisco activation and thylakoid reactions are not yet clear. Reactive oxygen species such as H2O2 may also be important during moderate heat stress. Rubisco can make hydrogen peroxide as a result of oxygenase side reactions and H2O2 production by rubisco was recently shown to increase substantially with temperature. The ability to withstand moderately high temperature can be improved by altering thylakoid lipid composition or by supplying isoprene. In my opinion this indicates that thylakoid reactions are important during moderate heat stress. The deactivation of rubisco at moderately high temperature could be a parallel deleterious effect or a regulatory response to limit damage to thylakoid reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01324.x
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  • 3
    Electronic Resource
    Electronic Resource
    Development of the capacity for isoprene emission in kudzu (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Isoprene is a biogenic hydrocarbon that has significant effects on tropospheric chemistry. It is emitted by a number of plant species, including kudzu, a leguminous vine that grows profusely in the south-eastern United States. This study investigated development of the capacity for isoprene emission in kudzu. Previous studies examined isoprene emission during leaf development, but a molecular explanation for the observed developmental delay in emission was lacking. This study found that kudzu leaves grown at a high temperature could emit isoprene at least a week before they were fully expanded and 1 d after becoming photosynthetically competent. When grown at low temperature, however, leaves did not emit isoprene until 1 week after they became fully expanded and 2 weeks after the onset of photosynthetic competence. Levels of mRNA and protein for isoprene synthase, which catalyses the final step in isoprene biosynthesis, were investigated; it was found that transcription and translation of this gene began at the same developmental stage as onset of emission in both growth conditions. Therefore, plant growth conditions, not leaf developmental stage, have primary control over expression of isoprene synthase and onset of kudzu isoprene emission. This finding may be useful in modelling early season isoprene emission rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01342.x
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  • 4
    Electronic Resource
    Electronic Resource
    Water stress, carbon dioxide, and light effects on sucrosephosphate synthase activity in Phaseolus vulgaris (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 81 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The characteristics of sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity in leaves of Phaseolus vulgaris L. cv. Linden was studied in plants subjected to water stress and various CO2 and light treatments. When water was withheld for 3 days causing mild water stress (–0.9 MPa), the activity of SPS measured in crude extracts was reduced ca 50%. The effect of water stress was most evident when the enzyme was assayed with saturating amounts of its substrates fructose 6-phosphate and UDP glucose. Placing a water-stressed plant in an atmosphere containing 1% CO2 reversed the effect of water stress on SPS activity over 5 h even though the water stress was not relieved. Holding unstressed leaves in low CO2 partial pressure reduced the extractable activity of SPS. After 1 h of low CO2 treatment the effect of low CO2 could be reversed by 20 min of 5% CO2. However, after 24 h of low CO2 treatment, less SPS activity was recovered by the 20 min treatment. The cytosolic protein synthesis inhibitor cycloheximide prevented the slow recovery of SPS activity, but did not affect the rapid recovery of SPS. We conclude that the effect of water stress on SPS activity was a consequence of the inhibition of photosynthesis caused by stomatal closure. Responses of Phaseolus vulgaris SPS to light were similar to the response to low CO2 in that the effects were most pronounced under Vmax assay conditions. This is the first report of this type of light response of SPS in a dicotyledonous species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb01709.x
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  • 5
    Electronic Resource
    Electronic Resource
    Estimating the rate of photorespiration in leaves (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 73 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photorespiration is the light-dependent evolution of CO2, which accompanies photosynthesis in C3plants. The four best known methods of measuring the rate of photorespiration have theoretical or technical problems, which make the results unreliable. However, the rate of photorespiration can be calculated from the rate of net CO2assimilation and the partial pressures of CO2and O2. Estimates of rates of photorespiration in the past and future can be made. The rate of photorespiration as a proportion of the rate of photosynthesis will fall to one half the current rate when the CO2level in the atmosphere doubles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb09205.x
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  • 6
    Electronic Resource
    Electronic Resource
    Why plants emit isoprene (1995)
    [s.l.] : Nature Publishing Group
    Nature 374 (1995), S. 769-769 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Global emission of isoprene (2-methyl-l, 3-butadiene) from vegetation is estimated at 3x10 g yr"1, similar to methane1. Because isoprene reacts very rapidly with hydroxyl radicals, it plays an important role in atmospheric chemistry2"4. Why plants emit isoprene has been a mystery since ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/374769a0
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of water stress on photosynthetic electron transport, photophosphorylation, and metabolite levels of Xanthium strumarium mesophyll cells (1982)
    Springer
    Planta 156 (1982), S. 199-206 
    Details
    ISSN: 1432-2048
    Keywords: Carbon reduction cycle intermediates ; Cells (isolated) ; Electron transport ; Photophosphorylation ; Photosynthesis (water stress) ; Water stress ; Xanthium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several component processes of photosynthesis were measured in osmotically stressed mesophyll cells of Xanthium strumarium L. The ribulose-1,5-bisphosphate regeneration capacity was reduced by water stress. Photophoshorylation was sensitive to water stress but photosynthetic electron transport was unaffected by water potentials down to-40 bar (-4 MPa). The concentrations of several intermediates of the photosynthetic carbon-reduction cycle remained relatively constant and did not indicate that ATP supply was limiting photosynthesis in the water-stressed cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393725
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  • 8
    Electronic Resource
    Electronic Resource
    On the relationship between isoprene emission and photosynthetic metabolites under different environmental conditions (1993)
    Springer
    Planta 189 (1993), S. 420-424 
    Details
    ISSN: 1432-2048
    Keywords: ATP ; Carbon metabolism ; Isoprene ; Mucuna (isoprene emission) ; Phosphoglyceric acid ; Quercus (isoprene emission)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isoprene emission is related to photosynthesis but the nature of the relationship is not yet known. To explore this relationship we have examined the rate of isoprene emission, photosynthesis, and the contents of photosynthetic metabolites in leaves of velvet bean (Mucuna deeringeniana L.) and red oak (Quercus rubra L.) in response to a light-to-dark transition and to changes in air composition. Isoprene emission fell when darkness was imposed and the drop was associated with reduced amounts of ribulose-1,5-bisphosphate and ATP. The rate of isoprene emission and ATP content were reduced to the same extent by exposure to low O2 or high CO2 partial pressures. Only when O2 and CO2 were simultaneously removed from the air did the rate of isoprene emission drop without a corresponding change in ATP. The results demonstrate that when carbon is not limiting, isoprene emission is highly correlated with ATP content. When synthesis of phosphoglyceric acid is inhibited, however, carbon availability may control isoprene production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194440
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  • 9
    Electronic Resource
    Electronic Resource
    Altered photosynthesis, flowering, and fruiting in transgenic tomato plants that have an increased capacity for sucrose synthesis (1995)
    Springer
    Planta 196 (1995), S. 327-334 
    Details
    ISSN: 1432-2048
    Keywords: Carbon partitioning ; Carbon dioxide acclimation ; Lycopersicon ; Photosynthesis ; Sucrose and starch synthesis ; Sucrose-phosphate synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis, leaf assimilate partitioning, flowering, and fruiting were examined in two lines of Lycopersicon esculentum Mill. transformed with a gene coding for sucrose-phosphate synthase (SPS) (EC 2.3.1.14) from Zea mays L. expressed from a tobacco ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit promoter. Plants were grown at either 35 or 65 Pa CO2 and high light (1000 μmol photons·m−2·s−1). Limiting and maximum SPS activities were significantly greater (up to 12 times) in the leaves of SPS-transformed lines for all treatments. Partitioning of carbon into sucrose increased 50% for the SPS transformants. Intact leaves of the control lines exhibited CO2-insensitivity of photosynthesis at high CO2 levels, whereas the SPS transformants did not exhibit CO2-insensitivity. The O2-sensitivity of photosynthesis was also greater for the SPS-transformed lines compared to the untransformed control when measured at 65 Pa CO2. These data indicate that the SPS transformants had a reduced limitation on photosynthesis imposed by end-product synthesis. Growth at 65 Pa CO2 resulted in reduced photosynthetic capacity for control lines but not for SPS-transformed lines. When grown at 65 Pa CO2, SPS transformed lines had a 20% greater photosynthetic rate than controls when measured at 65 Pa CO2 and a 35% greater rate when measured at 105 Pa CO2. Photosynthetic rates were not different between lines when grown at 35 Pa CO2. The time to 50% blossoming was reduced and the total number of inflorescences was significantly greater for the SPS transformants when grown at either 35 or 65 Pa CO2. At 35 Pa CO2, the total fruit number of the SPS transformants was up to 1.5 times that of the controls, the fruit matured earlier, and there was up to a 32% increase in total fruit dry weight. Fruit yield was not significantly different between the lines when grown at 65 Pa CO2. Therefore, there was not a strict relationship between yield and leaf photosynthesis rate. Flowering and fruit development of the SPS-transformed lines grown at 35 Pa CO2 showed similar trends to the controls grown at 65 Pa CO2. Incidences of blossom-end rot were also reduced in the SPS-transformed lines. These data indicate that altering starch/sucrose partitioning by increasing the capacity for sucrose synthesis can affect acclimation to elevated CO2 partial pressure and flowering and fruiting in tomato.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201392
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  • 10
    Electronic Resource
    Electronic Resource
    The relationship between steady-state gas exchange of bean leaves and the levels of carbon-reduction-cycle intermediates (1984)
    Springer
    Planta 160 (1984), S. 305-313 
    Details
    ISSN: 1432-2048
    Keywords: Phaseolus (gas exchange) ; Photosynthesis (intermediates) ; Ribulose-1,5-bisphosphate carboxylase-oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the gas-exchange characteristics of attached leaves of Phaseolus vulgaris L. and the pool sizes of several carbon-reduction-cycle intermediates was examined. After determining the rate of CO2 assimilation at known intercellular CO2 pressure, O2 pressure and light, the leaf was rapidly killed (〈0.1 s) and the levels of ribulose-1,5-bisphosphate (RuBP), 3-phosphoglyceric acid (PGA), fructose-1,6-bisphosphate, fructose-6-phosphate, glucose-6-phosphate, glyceraldehyde-3-phosphate, and dihydroxyacetone phosphate were measured. In 210 mbar O2, photosynthesis appeared RuBP-saturated at low CO2 pressure and RuBP-limited at high CO2 pressure. In 21 mbar (2%) O2, the level of RuBP always appeared saturating. Very high levels of PGA and other phosphate-containing compounds were found with some conditions, especially under low oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393411
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