Ratio of sugar concentrations in the phloem sap and the cytosol of mesophyll cells in different tree species as an indicator of the phloem loading mechanism

Fink, Daniel; Dobbelstein, Elena; Barbian, Andreas; Lohaus, Gertrud

doi:10.1007/s00425-018-2933-7

Cited by 26 publications

(14 citation statements)

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“…The phloem solute concentrations we estimate from our measurements of bulk leaf Suc concentration and data from the literature are narrowly sufficient to draw water in from the xylem and generate enough pressure to drive flow to the sinks, even with the conservative assumption of complete compartmentalization of the Suc to the cytoplasm. The few studies that have measured Suc compartmentalization suggest that it is not exclusively confined to the cytoplasm (Öner-Sieben and Lohaus, 2014;Fink et al, 2018). Therefore, our findings could be interpreted as providing support for a model characterized by mixed (Slewinski et al, 2013) or active loading for red oak, instead of purely passive loading, which would help drive up the Suc concentration in the phloem.…”

Section: Export Patternssupporting

confidence: 55%

Leaf Carbon Export and Nonstructural Carbohydrates in Relation to Diurnal Water Dynamics in Mature Oak Trees

et al. 2020

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Trees typically experience large diurnal depressions in water potential, which may impede carbon export from leaves during the day because the xylem is the source of water for the phloem. As water potential becomes more negative, higher phloem osmotic concentrations are needed to draw water in from the xylem. Generating this high concentration of sugar in the phloem is particularly an issue for the ;50% of trees that exhibit passive loading. These ideas motivate the hypothesis that carbon export in woody plants occurs predominantly at night, with sugars that accumulate during the day assisting in mesophyll turgor maintenance or being converted to starch. To test this, diurnal and seasonal patterns of leaf nonstructural carbohydrates, photosynthesis, solute, and water potential were measured, and carbon export was estimated in leaves of five mature (.20 m tall) red oak (Quercus rubra) trees, a species characterized as a passive loader. Export occurred throughout the day at equal or higher rates than at night despite a decrease in water potential to 21.8 MPa at midday. Suc and starch accumulated over the course of the day, with Suc contributing ;50% of the 0.4 MPa diurnal osmotic adjustment. As a result of this diurnal osmotic adjustment, estimates of midday turgor were always .0.7 MPa. These findings illustrate the robustness of phloem functioning despite diurnal fluctuations in leaf water potential and the role of nonstructural carbohydrates in leaf turgor maintenance.

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Section: Export Patternssupporting

confidence: 55%

Leaf Carbon Export and Nonstructural Carbohydrates in Relation to Diurnal Water Dynamics in Mature Oak Trees

et al. 2020

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“…Phloem exudates of bark tissues from A. alba and P. abies contained sucrose, glucose and fructose. In contrast, pure phloem sap normally does not contain glucose and fructose [2]. Ziegler and Mittler [46] collected phloem sap from P. abies with the help of aphid stylectomy and found that sucrose was the only sugar in the phloem.…”

Section: Origin Of Sugars In Honeydewmentioning

confidence: 99%

“…Ziegler and Mittler [46] collected phloem sap from P. abies with the help of aphid stylectomy and found that sucrose was the only sugar in the phloem. Hexoses in the phloem exudate stem mainly from artificially hydrolyzed sucrose by the activity of sucrose cleavage enzymes from the wounded surface of the bark [2]. This may also be assumed for A. alba, because the bark exudate also contained sucrose and glucose and fructose, but no other di-or trisaccharides.…”

Section: Origin Of Sugars In Honeydewmentioning

confidence: 99%

“…Many insects of the order Hemiptera, including most aphids and coccids, feed on the phloem sap of their respective host plants [1]. Phloem sap is generally dominated by sucrose, with concentrations ranging from 0.7 to 1.5 M [2,3,4]. Some plant species also translocate PLOS ONE | https://doi.org/10.1371/journal.pone.0228171 January 24, 2020 1 / 17 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111…”

Section: Introductionmentioning

confidence: 99%

“…sucrose, trehalose, maltose) and trisaccharides (e.g. melezitose, erlose, raffinose) were found in honeydew [15,17,19,20] but not in the phloem sap of several tree species, where only sucrose was present [2,21]. In willow trees, for example, sucrose was the only sugar found in the phloem sap, whereas the honeydew of a phloem feeding willow aphid (Tuberolachnus salignus) contained different mono-, di-, and trisaccharides [21].…”

Section: Introductionmentioning

confidence: 99%

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Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies

et al. 2020

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Several hemipteran species feed on the phloem sap of plants and produce large amounts of honeydew that is collected by bees to produce honeydew honey. Therefore, it is important to know whether it is predominantly the hemipteran species or the host plant to influence the honeydew composition. This is particularly relevant for those botanical and zoological species from which the majority of honeydew honey originates. To investigate this issue, honeydew from two Cinara species located on Abies alba as well as from two Cinara and two Physokermes species located on Picea abies were collected. Phloem exudates of the host plants were also analyzed. Honeydew of all species contained different proportions of hexoses, sucrose, melezitose, erlose, and further di-and trisaccharides, whereas the phloem exudates of the host trees contained no trisaccharides. Moreover, the proportions of sugars differed significantly between hemipteran species feeding on the same tree species. Sucrose hydrolysis and oligosaccharide formation was shown in whole-body homogenates of aphids. The type of the produced oligosaccharides in the aphid-extracts correlated with the oligosaccharide composition in the honeydew of the different aphid species. The total contents of amino acids and inorganic ions in the honeydew were much lower than the sugar content. Glutamine and glutamate were predominant amino acids in the honeydew of all six hemipteran species and also in the phloem exudates of both tree species. Potassium was the dominant inorganic ion in all honeydew samples and also in the phloem exudate. Statistical analyses reveal that the sugar composition of honeydew is determined more by the hemipteran species than by the host plant. Consequently, it can be assumed that the sugar composition of honeydew honey is also more influenced by the hemipteran species than by the host tree. OPEN ACCESSCitation: Shaaban B, Seeburger V, Schroeder A, Lohaus G (2020) Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies. PLoS ONE 15(1): e0228171. https://

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Strategies for Measuring Cytosolic Sugar Concentrations in Plant Cells

Li¹,

Liesche²

2022

Annual Plant Reviews Online

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The primary products of plant photosynthesis are soluble sugars such as glucose, fructose, and sucrose. These form the basis of every cell's carbon and energy metabolism. One major limitation for the investigation of soluble sugar metabolism is the difficulty associated with measuring their concentrations in different subcellular compartments. This applies especially to the cytosol, the site of many important enzymatic reactions, as it typically only fills a thin area between the vacuole and plasma membrane. In this article, we discuss the advantages and disadvantages of methods that have been used to probe cytosolic sugar concentrations, including microautoradiography, plasmolysis, non‐aqueous fractionation, Fourier transform infrared (FTIR) microspectroscopy, Raman microspectroscopy, mass spectrometry imaging, Förster resonance energy transfer (FRET) nanosensors, direct sampling, and theoretical modelling. Perspectives regarding different use cases and future developments are provided.

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Ratio of sugar concentrations in the phloem sap and the cytosol of mesophyll cells in different tree species as an indicator of the phloem loading mechanism

Cited by 26 publications

References 47 publications

Leaf Carbon Export and Nonstructural Carbohydrates in Relation to Diurnal Water Dynamics in Mature Oak Trees

Leaf Carbon Export and Nonstructural Carbohydrates in Relation to Diurnal Water Dynamics in Mature Oak Trees

Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies

Strategies for Measuring Cytosolic Sugar Concentrations in Plant Cells

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