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  • 2000-2004  (4)
  • 1990-1994  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Fructan contents and dry matter deposition in different tissues of the wheat grain during development (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The role of fructan metabolism in the assimilate relations of the grain of wheat (Triticum aestivum L.) was investigated by determination of the dry matter and fructan content of grain components at short intervals during grain filling. During the initial phase of rapid expansion, most of the assimilates entering the grain were partitioned to the outer pericarp. A large fraction of these assimilates were used for the synthesis of fructan. Dry matter deposition and fructan synthesis in the outer pericarp ceased at about 5d after anthesis. At the same time, the endosperm and the inner pericarp and testa started to accumulate dry matter at a fast rate. This was also associated with significant fructan synthesis in the latter tissues. The outer pericarp lost about 45% of its former maximum dry weight between 9 and 19 d after anthesis. This loss was due almost entirely to the near complete disappearance of water-soluble carbohydrates, most of which was fructan. The inner pericarp and testa accumulated dry matter until about mid-grain filling. The fructan contents of the inner pericarp and testa and the endosperm decreased slowly towards the end of grain filling. Most of the fructans in the inner pericarp and testa and the endosperm had a low molecular weight, whereas higher molecular weight fructans predominated in the outer pericarp. The embryo did not contain fructan. The presence of low molecular weight fructans in the endosperm cavity at mid-grain filling was confirmed. It is suggested that fructan synthesis is closely linked to growth-related water deposition in the different tissues of the wheat grain and serves to sequester the surplus of imported sucrose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1993.tb00859.x
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Defoliation effects on carbon and nitrogen substrate import and tissue-bound efflux in leaf growth zones of grasses (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Grassland plants suffer regular defoliation, causing loss of photosynthetic activity and internal resources. Consequently, re-foliation may be substrate-limited. The present study was undertaken to test the hypothesis that decreased C import in leaf growth zones is (partially) compensated by: (i) mobilization of substrate within growth zones; and (ii) increased efficiency of substrate use in leaf area expansion; but (iii) that these processes depend on the C status of growth zones at defoliation. Mixtures of a C3 (Lolium perenne L.) and a C4 grass (Paspalum dilatatum Poir.) were grown at 15 °C (C3 dominance) and 23 °C (C4 dominance). Individual plants thus grew in contrasting (light and temperature) environments before being defoliated. Defoliation caused a drastic and immediate decrease in C import, but effects on leaf area expansion were buffered by biomass mobilization in the growth zone and increases in specific leaf area of produced tissue. Thus, over the first 2 d post-defoliation, the amount of leaf area produced per unit imported C increased by 39 to 102% depending on treatment. The magnitude of these buffering responses was correlated with the concentration of water soluble carbohydrates in the growth zone at defoliation. Similar responses were observed for N, although defoliation effects were smaller and delayed relative to those on C import. This study demonstrates refoliation is sustained by short-term mobilization of reserves within the growth zone and reduced costs of produced leaf area, but that these mechanisms depend on growth zone C status at defoliation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2004.01147.x
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Spatial distribution of growth rates and of epidermal cell lengths in the elongation zone during leaf development in Lolium perenne L. (1990)
    Springer
    Planta 181 (1990), S. 423-431 
    Details
    ISSN: 1432-2048
    Keywords: Cell (growth, division) ; Kinematics (leaf growth) ; Leaf elongation rate ; Lolium (leaf growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Relative elemental growth rates (REGR) and lengths of epidermal cells along the elongation zone of Lolium perenne L. leaves were determined at four developmental stages ranging from shortly after emergence of the leaf tip to shortly before cessation of leaf growth. Plants were grown at constant light and temperature. At all developmental stages the length of epidermal cells in the elongation zone of both the blade and sheath increased from 12 μm at the leaf base to about 550 μm at the distal end of the elongation zone, whereas the length of epidermal cells within the joint region only increased from 12 to 40 μm. Throughout the developmental stages elongation was confined to the basal 20 to 30 mm of the leaf with maximum REGR occurring near the center of the elongation zone. Leaf elongation rate (LER) and the spatial distributions of REGR and epidermal cell lengths were steady to a first approximation between emergence of the leaf tip and transition from blade to sheath growth. Elongation of epidermal cells in the sheath started immediately after the onset of elongation of the most proximal blade epidermal cells. During transition from blade to sheath growth the length of the blade and sheath portion of the elongation zone decreased and increased, respectively, with the total length of the elongation zone and the spatial distribution of REGR staying near constant, with exception of the joint region which elongated little during displacement through the elongation zone. Leaf elongation rate decreased rapidly during the phase when only the sheath was growing. This was associated with decreasing REGR and only a small decrease in the length of the elongation zone. Data on the spatial distributions of growth rates and of epidermal cell lengths during blade elongation were used to derive the temporal pattern of epidermal cell elongation. These data demonstrate that the elongation rate of an epidermal cell increased for days and that cessation of epidermal cell elongation was an abrupt event with cell elongation rate declining from maximum to zero within less than 10 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195897
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