Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Strategies of Phloem Loading (1993)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 44 (1993), S. 253-281 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.44.060193.001345
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Ecophysiology of phloem loading in source leaves (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The nature of phloem loading of photosynthesis products – either symplastic or apoplastic – has been a matter of debate over the last two decades. This controversy was reconciled by proposing a multiprogrammed loading mechanism. Different modes of phloem loading were distinguished on the basis of the variety of plasmodesmatal connectivity between the minor vein elements. Physiological evidence for at least two phloem loading mechanisms as well as recent support for coincidence between plasmodesmatal connectivity and the loading mechanism is shortly reviewed. The present paper attempts to correlate the plasmodesmatal connectivity between sieve element/companion cell complex and the adjacent cells (the minor vein configuration) – and implicitly the associate phloem loading mechanisms – with different types of climate. The minor vein configuration is a family characteristic. This enables one to relate vein configuration with ecosystem using the family distribution over the globe. The uneven distribution of vein types between terrestrial ecosystems indicates that apoplastic phloem loading predominates in cold and dry climate zones. Projection of the minor vein configuration on the Takhtajan system of flowering plants suggests evolution from apoplastic to symplastic phloem loading. Accordingly, the distribution of minor vein configurations suggests that drought and temperature stress have led to the transformation of the ancient symplastic mode into the more advanced apoplastic mode of loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb00973.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The phloem, a miracle of ingenuity (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: This review deals with aspects of the cellular and molecular biology of the sieve element/companion cell complex, the functional unit of sieve tubes in angiosperms. It includes the following issues: (a) evolution of the sieve elements; (b) the specific structural outfit of sieve elements and its functional significance; (c) modes of cellular and molecular interaction between sieve element and companion cell; (d) plasmodesmal trafficking between sieve element and companion cell as the basis for macromolecular long-distance signalling in the phloem; (e) diversity of sieve element/companion cell complexes in the respective phloem zones (collection phloem, transport phloem, release phloem); (f) deployment of carriers, pumps and channels on the plasma membrane of sieve element/companion cell complexes in various phloem zones; and (g) implications of the molecular-cellular equipment of sieve element/companion cells complexes for mass flow of water and solutes in a whole-plant frame.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.00963.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    CO2 responsiveness of plants: a possible link to phloem loading (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: Of the many responses of plants to elevated CO2, accumulation of total non-structural carbohydrates (TNC in % dry weight) in leaves is one of the most consistent. Insufficient sink activity or transport capacity may explain this obvious disparity between CO2 assimilation and carbohydrate dissipation and structural investment. If transport capacity contributes to the problem, phloem loading may be the crucial step. It has been hypothesized that symplastic phloem loading is less efficient than apoplastic phloem loading, and hence plant species using the symplastic pathway and growing under high light and good water supply should accumulate more TNC at any given CO2 level, but particularly under elevated CO2. We tested this hypothesis by carrying out CO2 enrichment experiments with 28 plant species known to belong to groups of contrasting phloem-loading type. Under current ambient CO2 symplastic loaders were found to accumulate 36% TNC compared with only 19% in apoplastic loaders (P=0.0016). CO2 enrichment to 600 μmol mol−1 increased TNC in both groups by the same absolute amount, bringing the mean TNC level to 41% in symplastic loaders (compared to 25% in apoplastic loaders), which may be close to TNC saturation (coupled with chlornplast malfunction). Eight tree species, ranked as symplastic loaders by their minor vein companion cell configuration, showed TNC responses more similar to those of apoplastic herbaceous loaders. Similar results are obtained when TNC is expressed on a unit leaf area basis, since mean specific leaf areas of groups were not significantly different. We conclude that phloem loading has a surprisingly strong effect on leaf tissue composition, and thus may translate into alterations of food webs and ecosystem functioning, particularly under high CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00560.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Cell-cell communication in the leaves of Commelina cyanea and other plants (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The fluorescent probes 6–carboxyfluorescein and lucifer yellow CH which do not pass the plasmalemma have been used to examine cell-to-cell communication in the leaf of Commelina cyanea. Dye movement from cell-to-cell occurs in epidermal, spongy and palisade mesophyll, and vascular cells. Dye movement between these tissues was also found. Hence, the epidermis, spongy and palisade mesophyll cells, and vascular tissue are all linked in a continuous symplast. However, dye injected into the epidermal cells rarely moves into guard cells, indicating that these cells are relatively isolated from the surrounding cells. In the same way, guard cells in Vicia faba and the C4 grass Anthephora pubescens also appeared to be isolated from epidermal cells. Thus guard cell isolation from cell-to-cell communication appears to be a common phenomenon. Hence, the ion fluxes required for guard cell function must occur via the apoplast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604602
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A model for proton and potassium co-transport during the uptake of glutamine and sucrose by tomato internode disks (1979)
    Springer
    Planta 145 (1979), S. 77-82 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid uptake ; Lycopersicon ; Potassium co-transport ; Proton co-transport ; Sugar uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Internode disks of tomato (Lycopersicon esculentum cv. Moneymaker) were shaken in glutamine and sucrose solutions. At low external pH (〈±5.5), the uptake of these substances was accompanied with K+ efflux, at high pH (〉±5.5) with K+ influx. Low concentrations of external K+ (2 mmol l-1) stimulated the uptake of glutamine, which was strongly inhibited by the supply of high K+ concentrations (20 mmol l-1). The effect of K+ was particularly pronounced at high pH-values. Addition of CCCP in light reduced the uptake of glutamine to the same level as in the dark, and stopped the K+ fluxes which coincided with the uptake. A model is presented wherein the movements of K+ across the membrane are related to co-transport, depending on the membrane potential and the Nernst potential of K+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379930
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructural indications for coexistence of symplastic and apoplastic phloem loading in Commelina benghalensis leaves (1988)
    Springer
    Planta 176 (1988), S. 159-172 
    Details
    ISSN: 1432-2048
    Keywords: Apoplastic loading ; Commelina ; Minor vein ultrastructure ; Phloem loading ; Plasmodesmatal frequency ; Symplastic loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructural ontogeny of Commelina benghalensis minor-vein elements was followed. The mature minor vein has a restricted number of elements: a sheath of six to eight mestome cells encloses one xylem vessel, three to five vascular parenchyma cells, a companion cell, a thin-walled protophloem sieve-tube member and a thick-walled metaphloem sieve-tube member. The protophloem sieve-tube member (diameter 4–5 μm; wall thickness 0.12 μm) and the companion cell originated from a common mother cell. The metaphloem sieve-tube member (diameter 3 μm; wall thickness 0.2 μm) developed from the same precursor cell as the phloem parenchyma cells. Counting the plasmodesmatal frequencies demonstrated a symplastic continuum from mesophyll to the minor-vein phloem. The metaphloem sievetube member and the phloem parenchyma cells are the termini of this symplast. The protophloem sieve-tube member and companion cell constitute an insulated symplastic domain. The symplastic route, mesophyll to metaphloem sieve tube, appears to offer a path for symplastic loading; the protophloem sieve tube may be capable of accumulation from the apoplast. A similar two-way system of loading may exist in a number of plant families. Plasmodesmograms (a novel way to depict cell elements, plasmodesmatal frequencies and vein architecture) of some other species also displayed the anatomical requirements for two routes from mesophyll to sieve tube and indicate the potential coexistence of symplastic and apoplastic loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392441
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Phosphate uptake inLemna gibba G1: energetics and kinetics (1984)
    Springer
    Planta 161 (1984), S. 46-52 
    Details
    ISSN: 1432-2048
    Keywords: Lemna (phosphate uptake) ; Membrane potential ; Proton/phosphate cotransport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphate uptake was studied by determining [32P]phosphate influx and by measurements of the electrical membrane potential in duckweed (Lemna gibba L.). Phosphate-induced membrane depolarization (ΔE m ) was controlled by the intracellular phosphate content, thus maximal ΔE m by 1 mM H2PO 4 - was up to 133 mV after 15d of phosphate starvation. The ΔE m was strongly dependent on the extracellular pH, with a sharp optimum at pH 5.7. It is suggested that phosphate uptake is energized by the electrochemical proton gradient, proceeding by a 2H+/H2PO 4 - contransport mechanism. This is supported also by the fusicoccin stimulation of phosphate influx. Kinetics of phosphate influx and of ΔE m , which represent mere plasmalemma transport, are best described by two Michaelis-Menten terms without any linear components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00951459
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Uptake of [14C]sucrose in isolated minor-vein networks of Commelina benghalensis L (1985)
    Springer
    Planta 164 (1985), S. 362-369 
    Details
    ISSN: 1432-2048
    Keywords: Commelina ; Phloem loading ; Sucrose uptake ; Vein (isolation, sucrose uptake)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maceration with pectinase (4.5h) of Commelina benghalensis L. leaves stripped at either side yielded isolated vein networks consisting of four to five secondary veins and tertiary cross veins (=minor veins). Examination with Evans Blue and injection of Fluorescein F showed that 80% of the veins were viable. Proof of normal functioning of isolated minor veins was that [14C]sucrose fed to an apical vein network attached to the remaining intact part of the leaf was absorbed and finally arrived in the petiole. Sucrose uptake by veins obeyed Michaelis-Menten kinetics (K m 5·10-4 mol l-1; V max (light) 3.2 μmol h-1 g-1 fresh weight, V max (dark) 1.5 μmol h-1 g-1 fresh weight). A linear component, not inhibited by carbonylcyanide m-chlorophenylhydrazone and p-chloromercuribenzenesulfonic acid, was present. Maximal uptake took place at 5 mmol l-1 K+; concentrations of K+ higher than 10 mmol l-1 decreased the rate of uptake. The uptake rates by isolated veins and veins in situ (in disks) were in the same order of magnitude. Altogether, isolated veins promise to be a useful system for the study of loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402947
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Quantification of symplastic continuity as visualised by plasmodesmograms: diagnostic value for phloem-loading pathways (1992)
    Springer
    Planta 187 (1992), S. 359-366 
    Details
    ISSN: 1432-2048
    Keywords: C3, C4 plants ; Phloem loading (apoplastic, symplastic) ; Plasmodesmatal frequencies ; Plasmodesmogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The use of plasmodesmatal frequency to correlate cell-cell symplastic transport capacity remains a contentious problem, as variation in cell shape, accurate determination of interface contact area between cell types, distribution (i.e. whether random or aggregated) and shape (i.e. whether single or branched), and state of permeability may confuse the issue. Additionally, variation in the methods used to determine the frequencies compounds the problem further. Data presented in this paper show that plasmodesmograms offer a means to visualise the potential transport pathway from mesophyll cells to sieve tubes. Furthermore, the results allow an instant appreciation of symplastic continuity or discontinuity and, accordingly, the potential symplastic and-or apoplastic stages involved in the overall loading process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195659
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...