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  • 1
    Electronic Resource
    Electronic Resource
    Disentangling CO2 fluxes: direct measurements of mesocosm-scale natural abundance 13CO2/12CO2 gas exchange, 13C discrimination, and labelling of CO2 exchange flux components in controlled environments (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A 13C/12C mass spectrometer was interfaced with a open gas exchange system including four growth chambers to investigate CO2 exchange components of perennial ryegrass (Lolium perenne L.) stands. Chambers were fed with air containing CO2 with known δ13C (δCΟ2−2.6 or −46.8‰). The system did not fractionate C isotopes and no extraneous CO2 leaked into chambers. The on-line 13C discrimination (Δ) of ryegrass stands in light was independent of δCΟ2 when δCΟ2 was constant. The δ of CO2 exchanged by the stands in light (δNd) and darkness (δRn) differed by 0.7‰, suggesting some Δ in dark respiration at the stand-level. However, Δ decreased by ∼ 10‰ when δCΟ2 was switched from −46.8 to −2.5‰, and increased by ∼ 10‰ following a shift from −2.6 to −46.7‰ due to isotopic disequilibria between photosynthetic and respiratory fluxes. Isotopic imbalances were used to assess (non-photorespiratory) respiration in light and the replacement of the respiratory substrate pool(s) by new photosynthate. Respiration was partially inhibited by light, but increased during the light period and decreased in darkness, in association with temperature changes. The labelling kinetics of respiratory CO2 indicated the existence of two major respiratory substrate pools: a fast pool which was exchanged within hours, and a slow pool accounting for ∼ 60% of total respiration and having a mean residence time of 3.6 d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Cell growth analysis during steady and non-steady growth in leaves of perennial ryegrass (Lolium perenne L.) subject to defoliation (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of defoliation on leaf elongation rate (LER) and on the spatial distribution of epidermal cell lengths in the leaf growth zone was studied in vegetative main tillers of perennial ryegrass (Lolium perenne L. cv Modus) grown in a controlled environment. A new material approach was used to analyse the responses of epidermal cell expansion and production during the initial, non-steady growth phase following defoliation. The analysis involved assigning an identity to individual expanding cells, assessing the displacement and estimating the expansion of cells with assigned identity during day 1 and day 2 after defoliation. LER decreased by 34% during the first 2 d after defoliation and did not recover to the pre-defoliation rate within the 14 day regrowth period. Decreased LER on day 1 and day 2 after defoliation was associated with (i) a decrease in the length of the leaf growth zone; (ii) a decrease in the length at which epidermal cells stopped expanding; (iii) a reduced expansion of cells at intermediate growth stages; and (iv) a reduction in cell production (i.e. division) and an associated decrease in the number of expanding cells in the growth zone. However, defoliation had no effect on the expansion of cells located in the proximal part of the growth zone. Reduced LER at 14 d after defoliation was associated with a reduced cell production rate (27% lower than the pre-defoliation rate) and decreased final cell size (− 28%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00535.x
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon and nitrogen deposition in expanding tissue elements of perennial ryegrass (Lolium perenne L.) leaves during non-steady growth after defoliation (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: The effect of defoliation on the deposition of carbon (C) and nitrogen (N) and the contribution of reserves and current assimilates to the use of C and N in expanding leaf tissue of severely defoliated perennial ryegrass (Lolium perenne L.) was assessed with a new material element approach. This included 13C/12C-and 15N/14N-steady-state labelling of all post-defoliation assimilated C and N, analysis of tissue expansion and displacement in the growth zone, and investigation of the spatial and temporal changes in substrate and label incorporation in the expanding elements prior to and after defoliation. The relationship between elemental expansion and C deposition was not altered by defoliation, but total C deposition in the growth zone was decreased due to decreased expansion of tissue at advanced developmental stages and a shortening of the growth zone. The N deposition per unit expansion was increased following defoliation, suggesting that N supply did not limit expansion. Transition from reserve- to current assimilation-derived growth was rapid (〈1 d for carbohydrates and approximately 2 d for N), more rapid than suggested by label incorporation in growth zone biomass. The N deposition was highest near the leaf base, where cell division rates are greatest, whereas carbohydrate deposition was highest near the location of most active cell expansion. The contribution of reserve-derived relative to current assimilation-derived carbohydrates (or N) to deposition was very similar for elements at different stages of expansion
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00689.x
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  • 4
    Electronic Resource
    Electronic Resource
    C-isotope composition of CO2 respired by shoots and roots: fractionation during dark respiration? (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The CO2 respired by leaves is 13C-enriched relative to leaf biomass and putative respiratory substrates (Ghashghaie et al., Phytochemistry Reviews 2, 145–161, 2003), but how this relates to the 13C content of root, or whole plant respiratory CO2 is unknown. The C isotope composition of respiratory CO2 (δR) from shoots and roots of sunflower (Helianthus annuus L.), alfalfa (Medicago sativa L.), and perennial ryegrass (Lolium perenne L.) growing in a range of conditions was analysed. In all instances plants were grown in controlled environments with CO2 of constant concentration and δ13C. Respiration of roots and shoots of individual plants was measured with an open CO2 exchange system interfaced with a mass spectrometer. Respiratory CO2 from shoots was always 13C-enriched relative to that of roots. Conversely, shoot biomass was always 13C-depleted relative to root biomass. The δ-difference between shoot and root respiratory CO2 was variable, and negatively correlated with the δ-difference between shoot and root biomass (r2 = 0.52, P = 0.023), suggesting isotope effects during biosynthesis. 13C discrimination in respiration (R) of shoots, roots and whole plants (eShoot, eRoot, ePlant) was assessed as e = (δSubstrate − δR)/(1 + δR/1000), where root and shoot substrate is defined as imported C, and plant substrate is total photosynthate. Estimates were obtained from C isotope balances of shoots, roots and whole plants of sunflower and alfalfa using growth and respiration data collected at intervals of 1 to 2 weeks. eplant and eShoot differed significantly from zero. eplant ranged between −0.4 and −0.9‰, whereas eShoot was much greater (−0.6 to −1.9‰). eRoot was not significantly different from zero. The present results help to resolve the apparent conflict between leaf- and ecosystem-level 13C discrimination in respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01268.x
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