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  • 1
    Electronic Resource
    Electronic Resource
    Virus-induced differences in the response of oat plants to elevated carbon dioxide (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: Disease is an integral element of agricultural and natural systems, but the roles pathogens play in determining ecosystem response to elevated CO2 have rarely been examined. To investigate whether disease can alter the response of plants to CO2, we examined the effects of doubled CO2 (∼700 μmol mol−1) on Avena sativa infected with barley yellow dwarf virus (BYDV), a common pathogen of cereals and grasses. Oats infected with BYDV showed a significantly greater biomass response to CO2 enrichment than did healthy plants. Root mass of diseased plants increased by 37–60% with CO2 enrichment, but was largely unaffected in healthy plants. CO2 enrichment increased midday leaf-level photosynthesis and instantaneous water use efficiency by 34 and 93% in healthy plants and by 48 and 174% in infected plants. Foliar carbohydrates increased with both CO2 enrichment and BYDV infection, but the two factors affected individual pools dissimilarly. CO2 enrichment may alter the epidemiology of BYDV by increasing the persistence of infected plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-63.x
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  • 2
    Electronic Resource
    Electronic Resource
    Responses of photosynthesis and carbohydrate-partitioning to limitations in nitrogen and water availability in field-grown sunflower (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 14 (1991), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Sunflower plants (Helianthus annuus L., cv. CGL 208) were field-grown in adjacent plots of varying resource availability. Control plants received irrigation (on a 4–5 d interval) and high levels of fertilizer nitrogen. Nutrient-stress (N-stress) plants received control levels of irrigation but no nutrient amendments and were determined to be nitrogen-limited. Water-stress (H2O-stress) plants received control levels of fertilizer nitrogen, but no irrigation after approximately 6 weeks of plant growth. Both stress treatments reduced maximum and diurnal net photosynthesis (A) but resulted in different physiological or biochemical adjustments that tended to maintain or increase A per unit of resource (nitrogen or water) in shortest supply while decreasing the ratio of A per unit of abundant resource. Nutrient-stress reduced total foliar nitrogen, foliar chlorophyll, and initial and total RuBPCase activities, thereby enhancing or preserving photosynthetic nitrogen-use efficiency (NUE), defined as the maximum A observed per unit of leaf nitrogen, relative to the control and H2O-stress treatments. In addition, N-stress reduced photosynthetic water-use efficiency (WUE), defined as the ratio of A to stomatal conductance to water vapour (g). The slope of A versus g increased with H2O-stress. In addition, sunflower plants responded to H2O-stress by accumulating foliar glucose and sucrose and by exhibiting diurnal leaf wilting, which presumably provided additional improvements in photosynthetic WUE through osmoregulation and reduction of midday radiation interception respectively. Photosynthetic NUE was decreased by H2O-stress in that control levels of total nitrogen, foliar chlorophyll, and RuBPCase activities were maintained even after mean diurnal levels of A had fallen to less than 50% of the control level. We conclude that field-grown sunflower manages a trade-off between photosynthetic WUE and NUE, increasing use efficiency of the scarce resource while decreasing use efficiency of the abundant resource.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1991.tb00966.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stomatal responses to increased CO2: implications from the plant to the global scale (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Increased atmospheric CO2 often but not always leads to large decreases in leaf conductance. Decreased leaf conductance has important implications for a number of components of CO2 responses, from the plant to the global scale. All of the factors that are sensitive to a change in soil moisture, either amount or timing, may be affected by increased CO2. The list of potentially sensitive processes includes soil evaporation, run-off, decomposition, and physiological adjustments of plants, as well as factors such as canopy development and the composition of the plant and microbial communities. Experimental evidence concerning ecosystem-scale consequences of the effects of CO2 on water use is only beginning to accumulate, but the initial indication is that, in water-limited areas, the effects of CO2-induced changes in leaf conductance are comparable in importance to those of CO,2-induced changes in photosynthesis.Above the leaf scale, a number of processes interact to modulate the response of canopy or regional evapotran-spiration to increased CO2. While some components of these processes tend to amplify the sensitivity of evapo-transpiration to altered leaf conductance, the most likely overall pattern is one in which the responses of canopy and regional evapotranspiration are substantially smaller than the responses of canopy conductance. The effects of increased CO2 on canopy evapotranspiration are likely to be smallest in aerodynamically smooth canopies with high leaf conductances. Under these circumstances, which are largely restricted to agriculture, decreases in evapotranspiration may be only one-fourth as large as decreases in canopy conductance.Decreased canopy conductances over large regions may lead to altered climate, including increased temperature and decreased precipitation. The simulation experiments to date predict small effects globally, but these could be important regionally, especially in combination with radiative (greenhouse) effects of increased CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00630.x
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  • 4
    Electronic Resource
    Electronic Resource
    Predicting responses of photosynthesis and root fraction to elevated [CO2]a: interactions among carbon, nitrogen, and growth (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: At elevated atmospheric CO2 concentrations ([CO2]a), photosynthetic capacity (Amax) and root fraction (ηR, the ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible causes of this, focusing on the relative magnitudes of the effects of elevated [CO2]a on specific leaf (nm) and plant (np) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (α). In our survey of 39 studies with 35 species, we found that elevated [CO2]a led to decreased nm and np in all the studies and to increased h and α in most of the studies. The magnitudes of these changes varied with species and with experimental conditions.Based on a model that integrated [CO2]a-induced changes in leaf nitrogen into a biochemically based model of leaf photosynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (Amax will increase) when growth at increased [CO2]a leads to increases in h that are larger than decreases in nm. Photosynthesis will be downregulated (Amax will decrease) when increases in h are smaller than decreases in nm. The model suggests that photosynthetic capacity increases at elevated [CO2]a only when additional leaf mesophyll more than compensates the effects of nitrogen dilution.We considered two kinds of regulatory paradigms that could lead to varying responses of ηR to elevated [CO2]a, and compared the predictions of each with the data. A simple static model based on the functional balance concept predicts that ηR should increase when neither np nor h is very responsive to elevated [CO2]a. The quantitative and qualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts ηR from the relative sensitivities of photosynthesis and relative growth rate to elevated [CO2]a corresponds much more closely to the observations. In general, root fraction increases if the response of photosynthesis to [CO2]a is greater than that of relative growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb02017.x
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