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  • 1
    Electronic Resource
    Electronic Resource
    Interactions between plants: the role of mycorrhizae (1992)
    Springer
    Mycorrhiza 1 (1992), S. 47-53 
    Details
    ISSN: 1432-1890
    Keywords: Competition ; Grassland ; Nutrient transfer ; Nutrient cycling ; Seedling establishment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We present and discuss evidence, mostly from our own research, on some possible roles of mycorrhizae in interactions between plants. Experiments investigating whether seedlings become more rapidly infected with mycorrhiza if they are near large, already infected plants have shown that contact between the seedling's roots and established mycelium sometimes speeds up infection but on other occasions it does not. The reason for the discrepancies is not clear. Mycorrhiza can substantially alter the balance between competing plant species in a way that would not be predicted from their response when growing separately. An experiment involving large and small plants of the same species growing together showed little effect of mycorrhiza on the balance between plants of different sizes. The rate of transfer of 32P between plants of Lolium perenne or Plantago lanceolata was so slow, even when they were mycorrhizal, that phosphorus transfer between living plants seems unlikely to be of major ecological importance. However, nitrogen was found to be transferred much more freely than phosphorus between P. lanceolata plants. Situations are discussed in which there could be a source-sink relationship between plants causing net flow of carbon or mineral nutrients from one to the other. If nutrients pass from dying roots to living plants via mycorrhizal links, this could result in preferential nutrient cycling between species that share the same type of mycorrhiza. Some evidence is presented that this does happen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206135
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  • 2
    Electronic Resource
    Electronic Resource
    Soil insects alter fine root demography in peach (Prunus persica) (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: Minirhizotrons were used to assess the effects of soil insect suppression on the demography of peach fine roots (〈1 mm diameter) over two growing seasons. The experiment was conducted at the USDA–ARS Appalachian Fruit Research Station in Kearneysville, WV, USA using six 15-year-old peach trees. Clear butyrate minirhizotrons were installed beneath each tree in April 1996. Soil drench treatments were applied around individual minirhizotron tubes at monthly intervals and consisted of 1 L of water or 250 µL of a broad-spectrum insecticide in 1 L of water. Roots were videotaped at 2- to 4-week intervals during the 1996 and 1997 growing seasons. Insecticide application was associated with a significant increase in fine root longevity: the median lifespans of insecticide-treated roots were 46–125 d longer than those of control roots. In addition, the development of brown pigmentation was significantly delayed in insecticide-treated roots. Insecticide application did not appear to increase soil fertility, as accumulation of NO3–, NH4+, and PO42- on mixed bed ion-exchange resin was similar in treated and untreated soil. These results suggest that interactions with below-ground insects can significantly influence root longevity and may alter the rate at which roots undergo developmental changes in anatomy and physiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00793.x
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of temperature and soil drying on respiration of individual roots in citrus: integrating greenhouse observations into a predictive model for the field (2001)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In citrus, the majority of fine roots are distributed near the soil surface – a region where conditions are frequently dry and temperatures fluctuate considerably. To develop a better understanding of the relationship between changes in soil conditions and a plant’s below-ground respiratory costs, the effects of temperature and soil drying on citrus root respiration were quantified in controlled greenhouse experiments. Chambers designed for measuring the respiration of individual roots were used. Under moist soil conditions, root respiration in citrus increased exponentially with changes in soil temperature (Q10 = 1·8–2·0), provided that the changes in temperature were short-term. However, when temperatures were held constant, root respiration did not increase exponentially with increasing temperatures. Instead, the roots acclimated to controlled temperatures above 23 °C, thereby reducing their metabolism in warmer soils. Under drying soil conditions, root respiration decreased gradually beginning at 6% soil water content and reached a minimum at 〈2% soil water content in sandy soil. A model was constructed from greenhouse data to predict diurnal patterns of fine root respiration based on temperature and soil water content. The model was then validated in the field using data obtained by CO2 trapping on root systems of mature citrus trees. The trees were grown at a site where the soil temperature and water content were manipulated. Respiration predicted by the model was in general agreement with observed rates, which indicates the model may be used to estimate entire root system respiration for citrus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00723.x
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  • 4
    Electronic Resource
    Electronic Resource
    Soil CO2 concentration does not affect growth or root respiration in bean or citrus (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Contrasting effects of soil CO2 concentration on root respiration rates during short-term CO2 exposure, and on plant growth during long-term CO2 exposure, have been reported. Here we examine the effects of both short- and long-term exposure to soil CO2 on the root respiration of intact plants and on plant growth for bean (Phaseolus vulgaris L.) and citrus (Citrus volkameriana Tan. & Pasq.). For rapidly growing bean plants, the growth and maintenance components of root respiration were separated to determine whether they differ in sensitivity to soil CO2. Respiration rates of citrus roots were unaffected by the CO2 concentration used during the respiration measurements (200 and 2000 μmol mol−1), regardless of the soil CO2, concentration during the previous month (600 and 20 000 μmol mol−1). Bean plants were grown with their roots exposed to either a natural CO2 diffusion gradient, or to an artificially maintained CO2 concentration of 600 or 20 000 μmol mol−1. These treatments had no effect on shoot and root growth. Growth respiration and maintenance respiration of bean roots were also unaffected by CO2 pretreatment and the CO2 concentration used during the respiration measurements (200–2000 μmol mol−1). We conclude that soil CO2 concentrations in the range likely to be encountered in natural soils do not affect root respiration in citrus or bean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-52.x
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  • 5
    Electronic Resource
    Electronic Resource
    Root respiration in citrus acclimates to temperature and slows during drought (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Citrus seedlings were grown in soil columns in which the root system was hydraulically separated into two equal layers; this enabled us to maintain roots in the upper layer without water for 110 d. The columns were placed into waterbaths modified so that soil temperatures in the top layer could be maintained at 25°C or at 35°C, while temperature in the bottom layer was maintained at 25°C. We hypothesized that, if citrus plants were grown in dry soil for an extended period, root mortality would increase if the cost of maintaining the roots was increased by elevating the soil temperature. However, during the drought period we did not observe any root mortality, even at the higher soil temperature. Moreover, we did not find that root respiration was increased by prolonged exposure to drought and higher soil temperature. We did find that root respiration rates slowed in dry soil. Furthermore, when the soil columns were switched from one temperature treatment to another, root respiration rates in wet soil rapidly increased when moved to a higher temperature or rapidly decreased when moved to a lower temperature. But after only 4 d, respiration rates returned to their original level; root respiration in dry soil was not affected by either short-or long-term shifts in soil temperature. Root respiration in citrus appears to acclimate rapidly to changes in soil temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-36.x
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  • 6
    Electronic Resource
    Electronic Resource
    Rapid shifts in phosphate acquisition show direct competition between neighbouring plants (1987)
    [s.l.] : Nature Publishing Group
    Nature 327 (1987), S. 615-616 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We conducted two field experiments with Artemisia tridentata ssp. vaseyana (Rydb.) Beetle, a dominant shrub in western North America. One experiment was with a co-occurring grass, Agropyron spicatum (Pursh) Scribn. and Smith, and one with Agropyron desertorum (Fisch. ex Link) Schult., a grass from ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/327615a0
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  • 7
    Electronic Resource
    Electronic Resource
    A comparison of phosphorus and nitrogen transfer between plants of different phosphorus status (1990)
    Springer
    Oecologia 82 (1990), S. 342-347 
    Details
    ISSN: 1432-1939
    Keywords: Competition ; Defoliation ; Nutrient transfer ; Nutrient cycling ; Plantago lanceolata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study has two objections: (1) to compare transfers of phosphorus (32P) with nitrogen (15N) from undefoliated and defoliated mycorrhizal P-rich plants to an adjacent mycorrhizal plant and (2) to determine whether the improved nutrient status of a plant growing with a nutrient-rich plant is due primarily to movement of nutrients from roots of its nutrient-rich neighbor (= nutrient transfer) or to reduced nutrient uptake by its nutrient-rich neighbor (=shift in competition). Two plants of Plantago lanceolata were grown in a three-pot unit in which each of their root systems were split, with part in the central shared pot and part by themselves in an outside pot. There were three treatments: (1) no added P; (2) P added in the outer pot to only plant, termed the “donor” plant, since it might provide P to the companion plant, acting as a “receiver”; and (3) as in the previous treatment but the P-fertilized donor plant was also clipped. To encourage the formation of hyphal links between roots of the different plants, transfers were determined when root length densities were high (90 to 130 cm cm-3 soil) and when 56 to 85% of the root length was infected with vesicular-arbuscular mycorrhizae. Phosphorus fertilization enhanced P but not N movement within donor plants. Regardless of treatment, N transfer from donor to receiver plants was an order of magnitude greater than P transfer and in amounts that could potentially affect plant nutrition in very infertile soils. Phosphorus transfer was very small in any of the treatments. Although P fertilization and clipping improved P status of receiver plants, P transfer was not indicated as the main reason for the improved nutrition. A shift in competition between donor and receiver plants was likely the major factor in the shift in nutrition of the receiver plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317481
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  • 8
    Electronic Resource
    Electronic Resource
    Competitive ability is linked to rates of water extraction (1988)
    Springer
    Oecologia 75 (1988), S. 1-7 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron ; Artemisia ; Competition ; Competitive ability ; Water depletion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relative competitive abilities of Agropyron desertorum and Agropyron spicatum under rangeland conditions were compared using Artemisia tridentata ssp. wyomingensis transplants as indicator plants. We found A. desertorum to have substantially greater competitive ability than A. spicatum as manifested by the responses of Artemisia shrubs that were transplanted into nearly monospecific stands of these grass species. The Artemisia indicator plants had lower survival, growth, reproduction, and late-season water potential in the neighborhoods dominated by A. desertorum than in those dominated by A. spicatum. In similar, essentially monospecific grass stands, neutron probe soil moisture measurements showed that stands of A. desertorum extracted water more rapidly from the soil profile than did those of A. spicatum. These differences in extraction rates correlate clearly with the differences in indicator plant success in the respective grass stands. Nitrogen and phosphorus concentrations in Artemisia tissues suggested these nutrients were not limiting indicator plant growth and survival in the A. desertorum plots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378806
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  • 9
    Electronic Resource
    Electronic Resource
    Characteristics of successful competitors: an evaluation of potential growth rate in two cold desert tussock grasses (1987)
    Springer
    Oecologia 71 (1987), S. 167-173 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron ; Artemisia ; Relative growth rate ; Competition ; Tussock grass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Within the first few weeks after seedling emergence, Agropyron desertorum, a more competitive tussock grass, had a much higher mean relative growth rate (RGR) than Agropyron spicatum, a very similar, but less competitive species. However, beyond the early seedling stage, the two grasses had a remarkably similar whole-plant RGR in hydroponic culture and aboveground RGR in glasshouse soil, if root temperatures were above approximately 12°C. At soil temperatures between 5 and 12°C, A. desertorum exhibited a 66% greater aboveground RGR than A. spicatum (P〈0.05). Both species responded similarly to warming soil temperatures. In the field, however, tiller growth rates were generally similar. Neither species showed marked tiller elongation until a couple of weeks after snowmelt, by which time soil temperatures, at least to a depth of 10 cm, were above 12°C for a significant portion of the day. Aboveground biomass accumulation over a three-year period indicated that both grasses had similar potential growth rates whereas Artemisia tridentata ssp. vaseyana, a common neighbor planted in the same plots, had a much greater potential growth rate. The greater competitive ability of adult A. desertorum, as compared to A. spicatum, cannot be attributed to appreciable differences in potential growth rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377281
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  • 10
    Electronic Resource
    Electronic Resource
    Host genotype and the formation and function of VA mycorrhizae (1994)
    Springer
    Plant and soil 159 (1994), S. 179-185 
    Details
    ISSN: 1573-5036
    Keywords: carbon cost ; carbon expenditure ; citrus genotypes ; host-fungus compatibility ; mycorrhizal dependency ; root colonization rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract VA mycorrhizae, the most ancient type of mycorrhizal symbiosis, are present in the most phytogenetically advanced groups. Few plants have evolved mechanisms to completely prevent infection by VAM fungi. Yet, plant species that are less dependent on VA mycorrhizae for nutrient acquisition (e.g., grasses) generally have less root colonization in the field than more dependent species (e.g., Citrus). Among closely related Citrus genotypes, there is a greater tendency for less dependent species to limit the rate but not the extent of colonization, even in high-P soils. We hypothesize that colonization represents a significant carbon cost that may be regulated by the host genotype. Carbon expenditure on the fungus at high P may result in mycorrhizal-induced growth depression. The potential value of breeding plants for greater susceptibility to colonization will depend on the cost/benefit of VA mycorrhizae for the specific crop, soil and environmental conditions. Although the genetics and physiology of host control over VAM colonization are barely known, recently discovered mycorrhizal colonization mutants (myc-) of pea offer great promise for the study of host-fungus compatibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000107
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