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  • 1
    Electronic Resource
    Electronic Resource
    Protein Serine/Threonine Kinases of the MAPK Cascade (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 766 (1995), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1995.tb26684.x
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  • 2
    Electronic Resource
    Electronic Resource
    Physiology of the interaction of angiosperm parasites and their higher plant hosts (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Interactions between parasitic angiosperms and their hosts occur at the level of seed germination, haustorial development and resource transfer. Chemicals released from the host function as cues for host recognition, and trigger germination as well as haustorial initiation. Transpiration is a key process regulating solute transfer from host to parasite, and some parasitie plants have unusual stomatal characteristics. Although solute transfer is apoplastic, the haustorium appears to play a role in regulating solute composition. Host responses to infection are reviewed, and it is concluded that competition for water and solutes are unlikely to play a major role in determining reductions in host productivity: metabolic incompatability is suggested to be the major cause of this.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb01281.x
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  • 3
    Electronic Resource
    Electronic Resource
    The carbon canopy economy of the association between cowpea and the parasitic angiosperm Striga gesnerioides (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The association between the parasite Striga gesnerioides and cowpea (Vigna unguiculata) was investigated using measurements of growth and gas exchange together with calculations of the carbon budget of the association. Striga gesnerioides has a very low photosynthetic capacity coupled with high rates of respiration. Even at photosynthetic light saturation shoots exhibit no net carbon gain. Thus S. gesnerioides is highly dependent on its host for carbon as well as for water and inorganic solutes. It is estimated that 70% of the carbon transferred from host to parasite is used in parasite respiration. Infected cowpea had a lower photosynthetic capacity, at times less than half that of uninfected plants. Infection with S. gesnerioides reduced the growth of cowpea by 75%. Calculations indicate that the loss of carbon from the host by export to the parasite is more important than reduced photosynthetic capacity of the host in accounting for the observed growth reductions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb00975.x
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  • 4
    Electronic Resource
    Electronic Resource
    Growth and carbon allocation in Pennisetum typhoides infected with the parasitic angiosperm Striga hermonthica (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Growth and gas exchange measurements are used in conjunction with a carbon balance model to describe the millet (Pennisetum typhoides)–witchweed (Striga hermonthica) host—parasite association. Striga hermonthica reduces the growth of millet by 28% and radically alters the architecture of infected plants. Whilst grain yield and stem dry weight are reduced (by 80 and 53%, respectively), leaf and root growth are stimulated (by 41 and 86%, respectively). The difference in production between infected and uninfected millet plants can be accounted for by two processes: first, export of carbon to the parasite (accounting for 16% of the dry weight not gained); and second, parasite-induced reductions in host photosynthesis (accounting for 84% of the dry weight not gained). Striga hermonthica is dependent on carbon exported from the host, since the plant has low rates of photosynthesis coupled with high rates of respiration. The carbon balance model suggests that in mature S. hermonthica plants parasitic on millet, 85% of the carbon is host-derived. Carbon fluxes are also estimated using δ13C measurements, since S. hermonthica is a C3 plant parasitizing a C4 host. In conjunction with gas exchange measurements, these suggest that in root, stem and leaf of S. hermonthica, 87, 70 and 49% of carbon is hostderived, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb02140.x
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  • 5
    Electronic Resource
    Electronic Resource
    A carbon balance model of the sorghum-Striga hermonthica host-parasite association (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Growth and gas exchange measurements are used to formulate a carbon balance model to describe the sorghum-Striga hermonthica host-Parasite association. S. hermonthica reduces the growth and radically alters the architecture of infected sorghum plants. Grain and stem weight are reduced, whilst leaf and root biomass are maintained. Losses in host productivity result from two processes: export of carbon to the parasite and Parasite-induced reductions in host photosynthesis. The latter occurs before the emergence of the Parasite above ground and accounts for 80% of the Predicted loss in production over the lifecycle of the association. S. hermonthica is dependent on carbon exported from the host, since the plant has low rates of photosynthesis coupled with high rates of respiration. Host-derived carbon accounts for approximately one-third of the total parasite carbon requirement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01921.x
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  • 6
    Electronic Resource
    Electronic Resource
    Root production, turnover and respiration under two grassland types along an altitudinal gradient: influence of temperature and solar radiation (1998)
    Springer
    Oecologia 114 (1998), S. 20-30 
    Details
    ISSN: 1432-1939
    Keywords: Key words Root birth ; Root death ; Minirhizotrons ; Acclimation ; Carbon cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have measured the rates of root production and death and of root respiration in situ under two grasslands along an altitudinal gradient in the northern Pennines, UK, represented by a lowland site at 171 m in an agricultural setting, and three upland sites between 480 and 845 m. One grassland was dominated by Festuca ovina and was on a brown earth soil; the other was dominated by Juncus squarrosus and Nardus stricta and occurred on a peaty gley. The natural altitudinal gradient was extended by transplantation. Although root biomass and root production (estimated using minirhizotrons) both showed pronounced seasonal peaks, there was no simple altitudinal gradient in either variable, and neither root production nor root death rate was a simple function of altitude. Increased root accumulation in summer was a function of change in the length of the growing season, not of soil temperature. Root populations in winter were similar at all sites, showing that increased production at some sites was accompanied by increased turnover, a conclusion confirmed by cohort analyses. Respiration rate, measured in the field by extracting roots and measuring respiration at field temperature in an incubator, was unrelated to temperature. The temperature sensitivity of respiration (expressed as the slope of a plot of log respiration rate against temperature) showed no simple seasonal or altitudinal pattern. Both root growth (under Festuca) and respiration rate were, however, closely related to radiation fluxes, averaged over the previous 10 days for growth and 2 days for respiration. The temperature sensitivity of respiration was a function of soil temperature at the time of measurement. These results show that root growth and the consequent input of carbon to soil in these communities is controlled by radiation flux not temperature, and that plants growing in these upland environments may acclimate strongly to low temperatures. Most carbon cycle models assume that carbon fluxes to soil are powerfully influenced by temperature, but that assumption is based largely on short-term studies and must be reassessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050415
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  • 7
    Electronic Resource
    Electronic Resource
    Root production and turnover in an upland grassland subjected to artificial soil warming respond to radiation flux and nutrients, not temperature (1999)
    Springer
    Oecologia 120 (1999), S. 575-581 
    Details
    ISSN: 1432-1939
    Keywords: Key words Root birth ; Root death ; Minirhizotron ; Soil temperature ; PAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root demographic processes (birth and death) were measured using minirhizotrons in the soil warming experiments at the summit of Great Dun Fell, United Kingdom (845 m). The soil warming treatment raised soil temperature at 2 cm depth by nearly 3°C. The first experiment ran for 6 months (1994), the second for 18 (1995–1996). In both experiments, heating increased death rates for roots, but birth rates were not significantly increased in the first experiment. The lack of stimulation of death rate in 1996 is probably an artefact, caused by completion of measurements in late summer of 1996, before the seasonal demography was concluded: root death continued over the winter of 1995–1996. Measurements of instantaneous death rates confirmed this: they were accelerated by warming in the second experiment. In the one complete year (1995–1996) in which measurements were taken, net root numbers by the end of the year were not affected by soil warming. The best explanatory environmental variable for root birth rate in both experiments was photosynthetically active radiation (PAR) flux, averaged over the previous 5 (first experiment) or 10 days (second experiment). In the second experiment, the relationship between birth rate and PAR flux was steeper and stronger in heated than in unheated plots. Death rate was best explained by vegetation temperature. These results provide further evidence that root production acclimates to temperature and is driven by the availability of photosynthate. The stimulation of root growth due to soil warming was almost certainly the result of changes in nutrient availability following enhanced decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050892
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  • 8
    Electronic Resource
    Electronic Resource
    Root production and mortality under elevated atmospheric carbon dioxide (1995)
    Springer
    Plant and soil 187 (1995), S. 299-306 
    Details
    ISSN: 1573-5036
    Keywords: carbon cycle ; carbon dioxide ; minirhizotron ; mortality ; root demography ; turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An essential component of an understanding of carbon flux is the quantification of movement through the root carbon pool. Although estimates have been made using radiocarbon, the use of minirhizotrons provides a direct measurement of rates of root birth and death. We have measured root demographic parameters under a semi-natural grassland and for wheat. The grassland was studied along a natural altitudinal gradient in northern England, and similar turf from the site was grown in elevated CO2 in solardomes. Root biomass was enhanced under elevated CO2. Root birth and death rates were both increased to a similar extent in elevated CO2, so that the throughput of carbon was greater than in ambient CO2, but root half-lives were shorter under elevated CO2 only under a Juncus/Nardus sward on a peaty gley soil, and not under a Festuca turf on a brown earth soil. In a separate experiment, wheat also responded to elevated CO2 by increased root production, and there was a marked shift towards surface rooting: root development at a depth of 80–85 cm was both reduced and delayed. In conjunction with published results for trees, these data suggest that the impact of elevated CO2 will be system-dependent, affecting the spatio-temporal pattern of root growth in some ecosystems and the rate of turnover in others. Turrnover is also sensitive to temperature, soil fertility and other environmental variables, all of which are likely to change in tandem with atmospheric CO2 concentrations. Differences in turnover and time and location of rhizodeposition may have a large effect on rates of carbon cycling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017095
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