Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Biochemical regulation of isoprene emission (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Isoprene (C5H8) is emitted from many plants and has a substantial effect on atmospheric chemistry. There are several models to estimate the rate of isoprene emission used to calculate the impact of isoprene on atmospheric processes. The rate of isoprene synthesis will depend either on the activity of isoprene synthase or the availability of its substrate dimethylallyl pyrophosphate (DMAPP). To investigate long-term regulation of isoprene synthesis, the isoprene emission rate of 15 kudzu leaves was measured. The chloroplast DMAPP level of the five leaves with the highest emission rates and the five leaves with the lowest rates were determined by non-aqueous fractionation of the bulked leaf samples. Leaves with high basal emission rates had low levels of DMAPP whereas leaves with low basal emission rates had high DMAPP levels in their chloroplasts indicating that the activity of isoprene synthase exerts primary control over the basal emission rate. To investigate short-term regulation, isoprene precursors were fed to leaves. Feeding dideuterated deoxyxylulose (DOX-d2) to Eucalyptus leaves resulted in the emission of dideuterated isoprene. Results from DOX-d2 feeding experiments indicated that control of isoprene emission rate was shared between reactions upstream and downstream of the DOX entry into isoprene metabolism. In CO2-free air DOX always increased isoprene emission indicating that carbon availability was an important control factor. In N2, isoprene emission stopped and could not be recovered by adding DOX-d2. Taken together, these results indicate that the regulation of isoprene emission is shared among several steps and the relative importance of the different steps in controlling isoprene emission varies with conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0016-8025.2003.01059.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Ethylene production and ACC-accumulation in Agrobacterium tumefaciens-induced plant tumours and their impact on tumour and host stem structure and function (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ethylene emission from wild-type Agrobacterium tumefaciens (C58)-induced stem tumours of Ricinus communis was continuously measured with two different methods, process gas chromatography and photo-acoustic spectrometry. Ethylene production was as high as 700 pmol g FW–1 h–1, namely 140 times greater than emitted by non-tumourized control stems. It was highest in 5-week-old tumours, independent of light, depressed by anoxia and, during water deficit it was stimulated by rewatering. A remarkable concomitant CO-production was discovered. Accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC), the substrate of ACC-oxidase, preceded ethylene emission with a maximum 2 weeks after tumour induction. Simultaneously, the xylem in the tumour-adjacent host stem underwent drastic changes: it increased two to three times in thickness, vessel diameters decreased, the rays remained unlignified and became multiseriate. With increasing emission of ethylene aerenchyma developed in the non-transformed, tumour-surrounding tissue that formerly was stem cortex. Cotyledons reacted with epinastic symptoms indicating induction of senescence. The present results reveal an important role of ethylene, in addition to cytokinin and auxin, for the differentiation and physiology of A. tumefaciens-induced tumours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00488.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    CO-laser side-band spectrometer: Sub-Doppler heterodyne frequency measurements around 5 µm (1995)
    Springer
    Applied physics 61 (1995), S. 169-173 
    Details
    ISSN: 1432-0649
    Keywords: 07.65.Gj ; 33.20.Ea ; 42.72.Ai
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the realization of a tunable sub-Doppler heterodyne spectrometer with high absolute accuracy, employing side-band generation with a CO laser. The fixed-frequency CO-gas laser, working from 4.7 to 8.4µm, is made partially tunable by the use of microwave side-band generation in a CdTe Electro-Optical Modulator (EOM). This leads to tunable radiation of high spectral purity. We describe the design of the microwave EOM, adapted to the CO laser, its performance and its first application to highly accurate frequency measurements. The side-band radiation is used for sub-Doppler stabilization of the CO laser, while the carrier frequency is mixed with the frequencies of two CO2 reference lasers. As a first result, we present measurements of OCS transitions in the 4.9µm (61 THz) region, reaching an absolute accuracy of 30 kHz (Δν/ν = 5×1O−10). Further application of our spectrometer to calibration gases will establish a variety of InfraRed (IR) calibration standards with a new quality of accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01090939
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Photoacoustic trace-gas detection using a cw single-frequency parametric oscillator (1998)
    Springer
    Applied physics 66 (1998), S. 741-745 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 42.65; 82.80K
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 H6) at 3.34 μm using a widely tunable cw single-frequency optical parametric oscillator. The high frequency and power stability and the continuous tunability of the parametric oscillator make it ideally suited for this application. Detection sensitivities of 0.5 ppb for ethane are obtained, which is comparable to the best results previously obtained with intracavity detection using line-tunable CO overtone lasers. The flexibility and compact size of cw single-frequency parametric oscillators can lead to portable photoacoustic trace-gas detection systems for environmental monitoring and process control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050461
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    On-line monitoring of biogenic isoprene emissions using photoacoustic spectroscopy (2000)
    Springer
    Applied physics 70 (2000), S. 275-280 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 42.55; 42.62; 82.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Isoprene (C5H8) is one of the most important biogenic volatile organic compounds (VOCs) in the atmosphere. To calculate the impact of isoprene on atmospheric processes models have been developed that describe the isoprene release from plants. Measurements of this release require techniques for a fast, sensitive, on-line isoprene detection. Photoacoustic (PA) spectroscopy is applied here for the first time to monitor biogenic isoprene emissions. A CO overtone PA spectrometer is used for the detection, probing the C-H stretching vibrations in the 3 to 4 μm range. This allows us to detect isoprene down to a few ppb with a time resolution of one minute in a continuous gas flow. The number of laser lines can be adjusted to meet the requirements of the respective experiment in terms of time resolution and selectivity against other possibly interfering VOCs. This results in a highly versatile instrument for the isoprene detection in biological experiments. Furthermore, the infrared fingerprint offers the potential to detect different isoprene isotopomers simultaneously, thus allowing us to carry out on-line labelling experiments. The new apparatus was used to study the light dependence of isoprene emission from Eucalyptus globulus. The results demonstrate, that the detector system is a promising tool for the study of plant gas emissions. It allows the validation of existing emission models which are important for atmospheric processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050045
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...