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  • 1
    Digitale Medien
    Digitale Medien
    Displacement of frequently occurring heacy metals in autumn leaves of beech (Fagus sylvatica) (1987)
    Springer
    Trees 1 (1987), S. 164-171 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Deciduous trees ; Fagus sylvatica ; Autumn leaves ; Iron ; Lead ; Manganese ; Zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary By utilizing energy-dispersive X-ray microanalysis the heavy metals manganese, iron, zinc and lead were determined in different tissues of beech (Fagus sylvatica L.) autumn leaves. It was observed that all four metals were accumulated in sieve element-companion cell complexes of the leaf veins in the period from the green (2 October) to the brown (23 October) leaf coloration. Concomitantly, the concentration of these metals decreased in certain tissues of the stems subtending the leaves. The major reservoirs of heavy metals in the stems were periderm, cortex, pith and xylem rays. Since sieve element-companion cell complexes of the stems showed increasing metal concentrations during the transition from the green to the brown leaf stage, and since this temporary increase also occurred in the petiole phloem, it is inferred that symplastic transport can be used in addition to apoplastic transport for the displacement of heavy metals. It is assumed that the accumulation of heavy metals in the veins of autumn leaves indicates the deposition of surplus ions which are excluded when leaves are cast off.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00193559
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  • 2
    Digitale Medien
    Digitale Medien
    Mineral partitioning in the phloem during autumn senescence of beech leaves (1988)
    Springer
    Trees 2 (1988), S. 73-83 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Autumn leaves ; Fagus sylvatica ; Mineral retrieval ; Phloem transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary During the period of leaf senescence in fall, the minerals Mg, Ca, K, P, Cl, S, and Si were compared for occurrence and density in tissue compartments of leaf blade, petiole, and subtending stem of beech (Fagus sylvatica L.). Measurements were made by energy-dispersive X-ray microanalysis. The plant material was collected on 2,9, 16 and 23 October, and showed green, greenyellow, yellow, and red-brown autumn leaf coloration. Mg, K, and P were retrieved from the leaf blade prior to shedding, and deposited mainly in cortex and pith tissues of the stem. S and Ca remained in the leaf, and Si and Cl appeared to accumulate in the leaf prior to shedding. During the four stages of leaf senescence, the phloem compartments of the petiole showed considerable changes in mineral content. In addition, leaf senescence in several cases was accompanied by ion shifting from symplastic to apoplastic compartments and vice versa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00196752
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  • 3
    Digitale Medien
    Digitale Medien
    The induction of sun and shade leaves of the European beech (Fagus sylvatica L.): anatomical studies (1989)
    Springer
    Trees 3 (1989), S. 1-10 
    Details
    ISSN: 1432-2285
    Schlagwort(e): Differentiation ; Leaf primordia ; Fagus sylvatica ; Sun shade leaves
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Primordia from buds of sun and shade twigs of European beech (Fagus sylvatica L.) were collected six times a year for anatomical investigations. Differentiation into sun-leaf and shade-leaf primordia was first observed in early August. Sun-leaf primordia had five, and shade-leaf primordia four layers of mesophyll meristem cells. With potted graft unions of beeches possible structural changes of leaf primordia were investigated. Trees adapted to shade develop sun-leaf primordia when put into full daylight, provided the transfer happened before July. Trees adapted to full daylight developed leaf primordia which remained structurally sun-leaf primordia when the plant was kept under shade conditions. Shadeleaf branches of young beech trees cut in February in order to expose the shade buds to full daylight developed either shade leaves or intermediate shade/sun leaves. These experiments show that the subtending leaf may provide the developing axillary bud with photoassimilates, but its character, whether sun or shade leaf, has no influence on the character of the developing leaf primordia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00202394
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  • 4
    Digitale Medien
    Digitale Medien
    The influence of externally supplied sucrose on phloem transport in the maize leaf strip (1977)
    Springer
    Planta 137 (1977), S. 145-151 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Phloem transport ; Sucrose ; Zea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Sucrose (2,5–1000 mmol l−1), labeled with [14C]sucrose, was taken up by the xylem when supplied to one end of a 30-cm-long leaf strip of Zea mays L. cv. Prior. The sugar was loaded into the phloem and transported to the opposite end, which was immersed in diluted Hoagland's nutrient solution. When the Hoagland's solution at the opposite end was replaced by unlabeled sucrose solution of the same molarity as the labeled one, the two solutions met near the middle of the leaf strip, as indicated by radioautographs. In the dark, translocation of 14C-labeled assimilates was always directed away from the site of sucrose application, its distance depending on sugar concentration and translocation time. When sucrose was applied to both ends of the leaf strip, translocation of 14C-labeled assimilates was directed toward the lower sugar concentration. In the light, transport of 14-C-labeled assimilates can be directed (1) toward the morphological base of the leaf strip only (light effect), (2) toward the base and away from the site of sucrose application (light and sucrose effect), or (3) away from the site of sucrose application independent of the (basipetal or acropetal) direction (sucrose effect). The strength of a sink, represented by the darkened half of a leaf strip, can be reduced by applying sucrose (at least 25 mmol l−1) to the darkened end of the leaf strip. However, equimolar sucrose solutions applied to both ends do not affect the strength of the dark sink. Only above 75 mmol l−1 sucrose was the sink effect of the darnened part of the leaf strip reduced. Presumably, increasing the sucrose concentration replenishes the leaf tissue more rapidly, and photosynthates from the illuminated part of the leaf strip are imported to a lesser extent by the dark sink.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00387551
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  • 5
    Digitale Medien
    Digitale Medien
    Reactivation of phloem export in mature maize leaves after a dark period (1982)
    Springer
    Planta 155 (1982), S. 444-448 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Glucose ; Leaf (phloem activity) ; Phloem transport ; Starch ; Sucrose ; Zea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Mature leaves of corn plants (Zea mays L. cv. Prior) which were darkened for 48 h contain neither bundle-sheath starch nor glucose, and their sucrose content is below 5 μM. In such leaves phloem export has ceased. When re-illuminated, photosynthetic sucrose production starts without delay, but the sucrose: glucose ratio is 1.25:1. Obviously, most of the new-formed sugar is utilized locally. Labeling with 14CO2 has shown that phloen export starts 30 to 40 min after the onset of photosynthesis, when the sucrose: glucose ratio has increased to 13:1. The first newly formed starch can be detected when phloem export is reactivated. Glucose content remains constantly low af about 2 μM for at least 2 h, and it never exceeds 10 μM. Radioactivity in the exporting veins is about five times higher after 2 to 7 h of re-illumination than in the 14-h-day plant. Therefore, phloem export is either intensified during the period of reactivation or exported assimilates are partly unloaded along their way. Comparison of photosynthetic activity of equal-sized leaf strips has shown that both accumulation of photosynthates and radioactivity of exporting veins are about three times higher in the detached strip than in the strip which remained attached to the mother plant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00394474
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  • 6
    Digitale Medien
    Digitale Medien
    Mechanical pressure inhibits vessel development of xylogenic cambial derivatives of beech (Fagus sylvatica L .) (1997)
    Springer
    Trees 11 (1997), S. 349-355 
    Details
    ISSN: 0931-1890
    Schlagwort(e): Key words Constant external pressure ; Fagus sylvatica ; Fiber tracheid differentiation ; Two-dimensional PAGE ; Vessel element differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  Segments of standing beech stems (Fagus sylvatica) were put under mechanical pressure from the end of May, in order to investigate the influence of constant external pressure on the development of secondary vascular tissue. After 4 weeks, the new xylem increment was investigated anatomically in cross-sections. The first axial xylem derivatives of the new year’s increment had differentiated into normal vessel elements and fiber-tracheids. Application of the pressure girdle had no effect on fiber-tracheid development, but it inhibited vessel formation. Under pressure, changes in the two dimensional PAGE protein pattern were characterized by the appearance of two new protein species as well as by the absence of one species that occurs under regular growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00009678
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