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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two populations of perennial ryegrass (Lolium perenne L.) S23, selected for contrasting rates of yield and mature leal dark respiration, were used in this study. Since previous work showed that yield decreased severely in population GL66 due to mechanical perturbation, possible effects on respiration rates were examined. Apart from a transient increase in population GL72, there was no effect on the respiration rate but mechanical perturbation did affect other processes. Handling caused transpiration ratesinthe light to increas for GL72, and in the dark to decrease for GL66. In the logger term, the nitrogen content decreased in handled plants grown at high density. These results emphasize that handling plants should be reduced to a minimum since it might have major effect on several processes. It is concluded that the original selection for the Lolium population was indeed on contrasting rates in yield and respiration. Furthermore it is argued that the existence of low- and high-yielding genotypes can be attributed to the dissimilar responses of different genotypes to mechanical influence.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Given the close relationship between a plant's growth rate and its pattern of biomass allocation and the effects of abscisic acid (ABA) on biomass allocation, we studied the influence of ABA on biomass allocation and growth rate of wildtype tomato (Lycopersicon esculentum Mill. cv. Moneymaker) plants and their strongly ABA-deficient mutant sitiens. The relative growth rate of sitiens was 22% lower than that of the wildtype, as the result of a decreased specific leaf area. The net assimilation rate and the leaf weight ratio were not affected. The mutant showed a much higher transpiration rate and lower hydraulic conductance of the roots. These two factors resulted in sitiens having a significantly lower leaf water potential and turgor. resulting in reduced leaf expansion and, consequently, a lower specific leaf area relative to the wildtype. Addition of ABA to the sitiens roots resulted in phenotypic reversion to the wildtype. We conclude that the influence of ABA-deficiency on biomass allocation and relative growth rate is the result of altered water relations in the plants, rather than of a direct effect on sink strength of different plant organs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Are there intrinsic differences in the rates of photosynthesis, shoot- and root-respiration between inherently fast- and slow-growing monocotyledons at high and low nitrogen supply? To analyze this question we grew 5 monocotyledons, widely differing in their inherent relative growth rate at high and low nitrogen supply in a growth room. Nitrate was exponentially added to the plants, enabling us to compare inherent differences in plant characteristics, without any effect of species differences in the ability to take up nutrients.At high nitrogen supply, the fast-growing species from productive habitats had a higher photosynthetic nitrogen use efficiency and rate of root respiration than the slow-growing ones from unproductive habitats. Only minor differences were observed in their rates of photosynthesis and shoot respiration per unit leaf area. At low nitrogen supply, the rates of photosynthesis and shoot- and root respiration decreased for all species, even though there were no longer any differences in these processes between inherently fast- and slow-growing species. The photosynthetic nitrogen use efficiency increased for all species, and no differences were found among species.Differences in the photosynthetic nitrogen use efficiency among species and nitrogen treatments are discussed in terms of the utilization of the photosynthetic apparatus, whereas differences in respiration rate are discussed in terms of the energy demand for growth, maintenance and ion uptake and their related specific respiratory energy costs. It is concluded that the relatively high abundance of slow-growing species compared to fast-growing ones in unproductive habitats is unlikely to be explained by differences in rates of photosynthesis and respiration or in photosynthetic nitrogen use efficiency.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 89 (1993), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two populations of Lolium perenne L. S23 (perennial ryegrass), selected for differences in mature leaf dark respiration, were used in a non-destructive indexing system for individual plants, to determine growth parameters. Population GL66, selected for high respiratory rates and low yield, responded strongly to the indexing treatment, when grown at low plant density. Dry weights of all plant parts decreased strongly, as did dry matter percentages of the leaf blades. At high density this population demonstrated the same trend, but additionally allocation to the shoot increased. In contrast, GL72, selected for low respiratory rates and a high yield, responded only at a high plant density. It is argued that there might be a relation between the dissimilar response of the two populations to mechanical influences and the presence of the genotypes of the low-yielding population in the parent variety. The results also emphasize that non-destructive growth analyses can only be used when their effects on the plants are known.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper describes the effects of nitrgen supply on the partitioning of biomass and nitrogen of Agrostis vinealis(L.) Schreber and Corynephorus canescens(L.) Beauv., two perennial grasses of dry, nutrient-poor inland dunes, and their consequences for growth and gas exchange. At a given plant nitrogen concentration (PNC) the two species allocate the same relative amount of dry matter and nitrogen to their leaves. However, A. vinealis allocates more dry matter and nitrogen to its roots and less to its above-ground support tissue than C. canescens. Both the leaf weight ratio and leaf nitrogen ratio increase with increasing PNC. Despite species-specific differences in growth form and leaf morphology, the leaf area ratio and specific leaf area of the two species are similar, both at high and low PNC. At intermediate nitrogen supply, and thus intemediate PNC, however, A. vinealis has a higher leaf area ratio and specific leaf area than C. canescens.The two species exhibit a similar positive relationship when either the rate of net photosynthesis or the rate of shoot respiration are compared to the leaf nitrogen concentration, all expressed per unit leaf weight. The rate of net photosynthesis per unit Jeafnitrogen (PNUE) of the two species increases with decreasing leaf nitrogen concentration per unit leaf weight. C. canescens has a higher PNUE at low, and a lower PNUE at high leaf nitrogen concentration per unit leaf weight than A. vinealis. At non-limiting nitrogen supply, A. vinealis has a higher nitrogen productivity and net assimilation rate and a similar PNC and leaf area ratio as compared to C. canescens, which explains the higher relative growth rate (RGRmax) of A. vinealis. At growth-limiting nitrogen supply C. canescens achieves a similar relative growth rate at a lower PNC than A. vinealis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 85 (1992), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have assessed the activities of the cytochrome and alternative pathways in total respiration and their role in each stage of germination of Zea mays L. radicles. Throughout imbibition, the salicylhydroxamic acid (SHAM) concentration needed to inhibit the cyanide-resistant pathway, without any side effects, decreased from 15 mM in quiescent embryos to 5 mM at 72 h after imbibition. Electrons predominantly flowed through the cytochrome pathway although the alternative pathway was already present at early imbibition. The capacity of the alternative path was about 70% of the control rate of respiration. Its engagement progressively increased from 18% after 10 min of imbibition to 70% at the radicle emergence and then decreased to 50% at 96 h after imbibition, concomitant with the onset of radicle growth. The alternative pathway was, however, not essential for germination. The observed activity of the alternative path correlated with the monosaccharide (glucose + fructose) content, suggesting that the alternative pathway could be acting according to the ‘energy overflow model’. On the other hand, up to 24 h after imbibition at 16°C, maize radicles tolerate a severe desiccation, becoming intolerant at 72 h. On reimbibition of tolerant radicles, respiration increased immediately and the alternative pathway was rapidly engaged. At 72 h, no respiration was measured, indicating a total loss of the respiratory systems. The possible correlation between carbohydrate content, loss of desiccation tolerance and activity of the two respiratory pathways is discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The rates of growth, net rate of nitrate uptake and root respiration of 24 wild species were compared under conditions of optimum nutrient supply. The relative growth rate (RGR)of the roots of these species varied between 110 and 370 mg g-1 day-1 and the net rate of nitrate uptake between 1 and 7 mmol (g root dry weight)-1 day-1. The rate of root respiration was positively correlated with the RGR of the roots. Root respiration was also calculated from the measured rate of growth and nitrate uptake, using previously determined values for the costs of maintenance, growth and ion uptake of two slow-growing species. The calculated rate of respiration was slightly lower than the measured one for slow-growing species, but twice as high as measured rates for rapid-growing species. This discrepancy was not due to a relatively smaller electron flow through the alternative pathway and, consequently, a more efficient ATP production in the fast-growing species. Neither could variation in specific costs for root growth or maintenance explain these differences. Therefore, we conclude that fast-growing species have lower specific respiratory costs for ion uptake than slow-growing ones. Due partly to these lower specific costs of nutrient uptake, the fraction of respiration that rapid-growing species spend on anion uptake is lower than that of slow-growing species, in spite of the much higher rate of ion uptake of the fast-growing ones.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1939
    Keywords: Biomass partitioning ; Leaf area ratio ; Net assimilation rate ; Relative growth rate ; Specific leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Why do inherently fast-growing species from productive habitats generally have a higher rate of biomass production in short-term low-nitrogen experiments than slow-growing species from unproductive habitats, whereas the opposite is found in long-term experiments? Is this mainly due to inherent differences in biomass allocation, leaf characteristics or the plants' physiology? To analyse these questions we grew five monocotyledonous species from productive and unproductive habitats in a climate chamber at both high and low nitrogen supply. Nitrate was supplied exponentially, enabling us to compare inherent differences in morphological and physiological traits between the species, without any interference due to differences in the species' ability to take up nutrients. At high nitrogen supply, we found major inherent differences in specific leaf area and nitrogen productivity, i.e. daily biomass increment per unit plant nitrogen, where-as there were only small differences in net assimilation rate, i.e. daily biomass increment per unit leaf area, and biomass partitioning. We propose that the higher specific leaf area and nitrogen productivity of inherently fast-growing species are the key factors explaining their high abundance in productive habitats compared with inherently slow-growing ones. At low nitrogen supply, the net assimilation rate was decreased to a similar extent for all species, compared with that at high nitrogen supply. The nitrogen productivity of the inherentlyfast-growing species decreased with decreasing nitrogen supply, whereas that of the inherently slow-growing species remained constant. There were no inherent differences in nitrogen productivity in this treatment. At this low nitrogen supply, the inherently fast-growing species invested relatively more biomass in their roots that the slow-growing ones did. The inherently fast-growing species still had a higher specific leaf area at low nitrogen supply, but the difference between species was less than that at high nitrogen supply. Based on the present results and our optimization model for carbon and nitrogen allocation (Van der Werf et al. 1993a), we propose that the relatively large investment in root biomass of fast-growing species is the key factor explaining their higher biomass production in short-term experiments. We also propose that in the long run the competitive ability of the slow-growing species will increase due to a lower turnover rate of biomass. It is concluded that the plant's physiology (net assimilation rate and nitrogen productivity), only plays a minor role in the species' competitive ability in low-nitrogen environments.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2048
    Keywords: Brachypodium ; Oxygen uptake ; Peroxidase and root respiration ; Respiration (residual, alternative and cytochrome pathways) ; Root respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study describes the O2 uptake characteristics of intact roots of Brachypodium pinnatum. In the presence of 25 mM salicylhydroxamic acid (SHAM), concentrations of KCN below 3.5 νM had no effect on the rate of root respiration, whereas in the absence of 25 mM SHAM a significant inhibition of approx. 18% was observed. This indicates that an O2-consuming reaction, not associated with the cytochrome pathway, the alternative pathway or the “residual component”, operates in the absence of any inhibitors in roots of B. pinnatum. We demonstrate here that this fourth O2-consuming reaction is mediated by a peroxidase. A peroxidase which catalyzed O2 reduction in the presence of NADH was readily washed from the roots of B. pinnatum. This peroxidase was stimulated by 5 mM SHAM, whereas ascorbic acid, catalase, catechol, gentisic acid, low concentrations potassium cyanide (3.5 μM), sodium azide, sodium sulfide, superoxide dismutase and high concentrations SHAM (25 mM) inhibited this reaction. Except for high concentrations of SHAM and concentrations of KCN higher than approx. 3.5 μM, these effectors could not be used to inhibit the peroxidase-mediated O2 uptake in intact roots of B. pinnatum. Concentrations of SHAM below 10 mM stimulated O2 uptake up to 15% of the control rate, depending on concentration, whereas 25 mM SHAM inhibited O2 uptake by 35%. The stimulation at low concentrations resulted from a SHAM-stimulated peroxidase activity, whereas 25 mM SHAM completely inhibited both the peroxidase-mediated O2 uptake and the activity of the alternative pathway. A method is presented for determining the relative contributions of each of the four O2-consuming reactions, i.e. the cytochrome pathway, the alternative pathway, the “residual component” and the peroxidase-mediated O2 uptake. The peroxidase-mediated O2 uptake contributed 21% to the total rate of oxygen uptake in roots of B. pinnatum, the cytochrome pathway contributed 41%, the alternative pathway 14% and the “residual component” 24%.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 148 (1993), S. vii 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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