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  • 1
    Electronic Resource
    Electronic Resource
    Costs and benefits of mycorrhizas: Implications for functioning under natural conditions (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 350-355 
    Details
    ISSN: 1420-9071
    Keywords: Mycorrhizas ; cost-benefit analysis ; phosphate uptake ; field conditions ; vesicular-arbuscular mycorrhizas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary It is paradoxical that most plants under natural conditions are infected with vesicular-arbuscular mycorrhizal fungi, yet that it is often difficult to demonstrate that infected plants receive any benefit from the association. The costs and benefits of infection are analysed and a hypothesis formulated that infection only yields benefits at times during the life cycle when P demand by the plant exceeds the capacity of the root system. A simulation model is described that suggests that infection density should be more or less constant below a threshold value of root P uptake rate, but that above this value roots should be non-mycorrhizal. More extensive study of mycorrhizas under field conditions is needed to test such predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01972076
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal acclimation of leaf and root respiration: an investigation comparing inherently fast- and slow-growing plant species (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We investigated the extent to which leaf and root respiration (R) differ in their response to short- and long-term changes in temperature in several contrasting plant species (herbs, grasses, shrubs and trees) that differ in inherent relative growth rate (RGR, increase in mass per unit starting mass and time). Two experiments were conducted using hydroponically grown plants. In the long-term (LT) acclimation experiment, 16 species were grown at constant 18, 23 and 28 °C. In the short-term (ST) acclimation experiment, 9 of those species were grown at 25/20 °C (day/night) and then shifted to a 15/10 °C for 7 days. Short-term Q10 values (proportional change in R per 10 °C) and the degree of acclimation to longer-term changes in temperature were compared. The effect of growth temperature on root and leaf soluble sugar and nitrogen concentrations was examined. Light-saturated photosynthesis (Asat) was also measured in the LT acclimation experiment. Our results show that Q10 values and the degree of acclimation are highly variable amongst species and that roots exhibit lower Q10 values than leaves over the 15–25 °C measurement temperature range. Differences in RGR or concentrations of soluble sugars/nitrogen could not account for the inter-specific differences in the Q10 or degree of acclimation. There were no systematic differences in the ability of roots and leaves to acclimate when plants developed under contrasting temperatures (LT acclimation). However, acclimation was greater in both leaves and roots that developed at the growth temperature (LT acclimation) than in pre-existing leaves and roots shifted from one temperature to another (ST acclimation). The balance between leaf R and Asat was maintained in plants grown at different temperatures, regardless of their inherent relative growth rate. We conclude that there is tight coupling between the respiratory acclimation and the temperature under which leaves and roots developed and that acclimation plays an important role in determining the relationship between respiration and photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00611.x
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  • 3
    Electronic Resource
    Electronic Resource
    Morphometric analysis of root systems: application of the technique and influence of soil fertility on root system development in two herbaceous species (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 5 (1982), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A method for describing root systems based on geomorphological techniques developed for river systems is described. Root systems, in common with other natural branching structures (rivers, bronchioles, trees), appear to obey Morton's Law of Branching: there is a constant ratio, the bifurcation or branching ratio, Rb, between the number of branches of a given order, Nu, and that of the next order. Nu+1, In experiments where Poa annua, and Rumex cripus, were grown at two levels of fertility, the first-order roots (the youngest members in this system) were generally unresponsive to fertility, and differences in the root systems were largely the result of changes in the second-order roots, those formed at the junction of two first-order roots. These differences were reflected in the branching ratio, Rb Although it is possible to explain these results by a stochastic model of branch development, the Rb values for roots are higher than for other natural branching structures, and higher than the random model predicts. It is possible that a model based on optimum exploration of space may be more appropriate and provide a key to the factors governing root branching patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11573079
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  • 4
    Electronic Resource
    Electronic Resource
    Why plants bother: root proliferation results in increased nitrogen capture from an organic patch when two grasses compete (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated whether the capacities of Lolium perenne L. and Poa pratensis L. roots to proliferate locally and to alter local nitrogen (N) inflows in a decomposing organic matter patch were important in their capture of N when grown together. In the presence of a patch, plants of both species were significantly heavier and contained more N. Root length and weight densities increased in the patch, but specific root length was unaltered. Although both species proliferated roots in the patch, L. perenne produced greater root length densities than P. pratensis, and also captured more N from the patch. Indeed, total N uptake from the patch was related to root length density within the patch. N inflows (rate of N uptake per unit root length) in the patch were no faster than in the whole root system for both species. Under the conditions of this study, root proliferation in an organic patch was more important for N capture from the patch than alterations in N inflows. Local proliferation of roots may be a key factor in interspecific competition for non-uniformly distributed supplies of N in natural habitats, so resolving the previous uncertainty as to the ‘adaptive’ nature of root proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00454.x
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  • 5
    Electronic Resource
    Electronic Resource
    Growth temperature influences the underlying components of relative growth rate: an investigation using inherently fast- and slow-growing plant species (2002)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 25 (2002), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We examined the effect of growth temperature on the underlying components of growth in a range of inherently fast- and slow-growing plant species. Plants were grown hydroponically at constant 18, 23 and 28 °C. Growth analysis was conducted on 16 contrasting plant species, with whole plant gas exchange being performed on six of the 16 species. Inter-specific variations in specific leaf area (SLA) were important in determining variations in relative growth rate (RGR) amongst the species at 23 and 28 °C but were not related to variations in RGR at 18 °C. When grown at 18 °C, net assimilation rate (NAR) became more important than SLA for explaining variations in RGR. Variations in whole shoot photosynthesis and carbon concentration could not explain the importance of NAR in determining RGR at the lower temperatures. Rather, variations in the degree to which whole plant respiration per unit leaf area acclimated to the different growth temperatures were responsible. Plants grown at 28 °C used a greater proportion of their daily fixed carbon in respiration than did the 18 and 23 °C-grown plants. It is concluded that the relative importance of the underlying components of growth are influenced by growth temperature, and the degree of acclimation of respiration is of central importance to the greater role played by NAR in determining variations in RGR at declining growth temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00879.x
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular diversity of arbuscular mycorrhizal fungi colonising arable crops (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 36 (2001), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We used differences in small subunit ribosomal RNA genes to identify groups of arbuscular mycorrhizal fungi that are active in the colonisation of plant roots growing in arable fields around North Yorkshire, UK. Root samples were collected from four arable fields and four crop species, fungal sequences were amplified from individual plants by the polymerase chain reaction using primers NS31 and AM1. The products were cloned and 303 clones were classified by their restriction pattern with HinfI or RsaI; 72 were subsequently sequenced. Colonisation was dominated by Glomus species with a preponderance of only two sequence types, which are closely related. There is evidence for seasonal variation in colonisation in terms of both level of colonisation and sequence types present. Fungal diversity was much lower than that previously reported for a nearby woodland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2001.tb00841.x
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  • 7
    Electronic Resource
    Electronic Resource
    Ploughing up the wood-wide web? (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 431-431 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Key species groups that affect major ecological processes are vital components of community diversity. Many such key groups are found in the soil, including the mycorrhizal fungi that may connect plants into a functional “wood-wide web”. Arbuscular mycorrhizal associations are ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/28764
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Rhizosphere and root-infecting fungi and the design of ecological field experiments (1995)
    Springer
    Oecologia 102 (1995), S. 230-237 
    Details
    ISSN: 1432-1939
    Keywords: Rhizosphere fungi ; Root-infecting fungi ; Fungicide ; Vulpia ciliata ssp. ambigua ; Annual plant performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As part of a wider study into the role of soil fungi in the ecology of the winter annual grass, Vulpia ciliata ssp. ambigua (Le Gall) Stace & Auquier, we applied the fungicides benomyl and prochloraz to three natural populations of the grass growing in East anglia, United Kingdom. The rhizosphere and rootinfecting fungi associated with the three populations were analysed each month between February and May 1992 when plants set seed. There were marked differences between the fungal floras associated with each of the three populations of V. ciliata, despite the fact that associated plant species and soil nutrient status were broadly similar between sites. This was attributed to wide differences in soil pH between the three populations. Prochloraz did not affect fungal abundance, but benomyl decreased the isolation frequencies of Fusarium oxysporum from roots and the frequencies of Penicillium and Trichoderma spp. isolated from rhizosphere soil, and increased the frequency of isolation of Mucor hiemalis from the rhizosphere of V. ciliata. There were also significant increases in the isolation frequencies of F. oxysporum from roots and M. hiemalis, Trichoderma spp. and Phoma fimeti from the rhizosphere of V. ciliata as plants matured. The significance of these results for the design of ecological field experiments are discussed in light of a previous study which has shown that asymptomatic root-infecting fungi can affect plant fecundity and hence abundance in natural populations of V. ciliata. We propose that differences in microbial communities between sites, controlled in part by soil chemistry, are a major factor determining plant performance under field conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333255
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  • 10
    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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