Evidence for the Consequences of a Barrier to Solute Diffusion Between the Apoplast and Vascular Bundles in Sugarcane Stalk Tissue

1992 ◽  
Vol 19 (6) ◽  
pp. 611 ◽  
Author(s):  
GE Welbaum ◽  
FC Meinzer ◽  
RL Grayson ◽  
KT Thornham
Keyword(s):  
Free Space ◽  
Xylem Sap ◽  
Dry Weight ◽  
Solute Diffusion ◽  
Vascular Bundles ◽  
Storage Tissue ◽  
Sugarcane Stalk ◽  
Large Molecular Weight ◽  
Osmotic Water ◽  
Storage Parenchyma

In a previous study we found that the apoplast of mature sugarcane stalk tissue contains up to 700 mM sucrose. In the current study, we found that xylem sap, exuded under root pressure from decapitated stalks, was virtually free of sucrose. This suggested that the apoplast of sugarcane stalk tissue contains at least two separate compartments: one within the free space of the vascular bundles, which is nearly free of sucrose, and another in the free space of the surrounding storage tissue. Anatomical observations indicated that these putative compartments were separated by the sclerenchymatous bundle sheath cell walls that were suberised and lignified early in development, constituting a barrier to the movement of relatively large molecular weight solutes but not water. It was hypothesised that this semipermeability would enable sucrose and other solutes in the apoplast of the storage tissue to provide a gradient for osmotic water flow from the xylem, generating a hydrostatic pressure in the apoplast. Additional lines of evidence were obtained to support this hypothesis: (i) apoplastic dyes were restricted to the xylem and did not accumulate in the apoplast of storage tissue when water-stressed plants were rehydrated, (ii) water potential measured with in situ psychrometers decreased when sections of intact stalks were cut, (iii) mature internode tissue of well-watered plants often cracks after maximum fresh and dry weight accumulation, and (iv) internode sections typically shrink in diameter immediately upon excision. The existence of a semipermeable barrier separating the vascular bundles from the storage parenchyma apoplast would require that phloem unloading involve a symplastic step in order to traverse the barrier. The presence of plasmodesmatal connections between companion, sclerenchyrna, and storage parenchyma cells supported this conclusion.

The anatomy of the pathway of sucrose unloading within the sugarcane stalk

2005 ◽  
Vol 32 (4) ◽  
pp. 367 ◽  
Author(s):  
Kerry B. Walsh ◽  
Russell C. Sky ◽  
Sharon M. Brown
Keyword(s):  
Cell Layer ◽  
Sink Strength ◽  
Vascular Bundles ◽  
Sucrose Transport ◽  
Long Distance ◽  
Long Distance Transport ◽  
Sugarcane Stalk ◽  
Storage Parenchyma ◽  
Phloem Fibre ◽  
Distance Transport

The physical path of sucrose unloading in the sugarcane stalk is described. About 50% of the vascular bundles in the internodes were located within 3 mm of the outside of the stalk. These bundles were inactive in long distance sucrose transport, as assessed by dye tracers of phloem flow. A sheath of fibres isolates the phloem apoplast from that of the storage parenchyma. In bundles associated with long distance transport (i.e. in the central region), the fibre sheath is narrowest to either side of the phloem fibre cap, and consists of living cells with plasmodesmata within pits in the secondary wall. Plasmodesmata were also arranged into pit fields between cells of the storage parenchyma. Since the vascular apoplast is isolated from the apoplast of the storage parenchyma, sucrose must move through the symplast of the fibre sheath. The calculated flux of sucrose through plasmodesmata of this cell layer was at the low end of reported values in the literature. Sucrose unloading within the storage parenchyma may also follow a symplastic route, with unloading into the apoplast of the storage parenchyma occurring as part of a turgor mechanism to increase sink strength.

scholarly journals SELECTION CRITERIA IN THE SEEDLING STAGE FOR PREDICTING APPLE ROOTSTOCK VIGOR

1977 ◽  
Vol 57 (3) ◽  
pp. 667-674 ◽  
Author(s):  
S. R. MILLER
Keyword(s):  
Selection Criteria ◽  
Xylem Sap ◽  
Amino Nitrogen ◽  
Growth Control ◽  
Dry Weight ◽  
Apple Rootstocks ◽  
Wheat Growth ◽  
Satisfactory Method ◽  
Size Controlling ◽  
Total P

Growth measurements made on the apple cvs. McIntosh and Quinte grafted on 12 Ottawa rootstock selections were related to 10 measurements of predicting rootstock vigor. Potential vigor was assessed by three calculations of bark percentage in the roots, leaf weight of trees in the nursery or stoolbeds, the wheat growth bioassay, leaf respiration and level of amino nitrogen, and total P and K in the xylem sap of the ungrafted clones. Of the 10 indices, dry weight of the leaves of the ungrafted apple rootstocks growing in the nursery or in stoolbeds was the most satisfactory method of assessing potential early vegetative growth. The ungrafted rootstocks that resulted in most growth control had the largest leaves. Data obtained are discussed in relation to developing a method of selecting rootstocks with size-controlling potential.

Ion behavior in plant cell walls. II. Measurement of the Donnan free space, anion-exclusion space, anion-exchange capacity, and cation-exchange capacity in delignified Sphagnum russowii cell walls

1989 ◽  
Vol 67 (2) ◽  
pp. 460-465 ◽  
Author(s):  
Conrad Richter ◽  
Jack Dainty
Keyword(s):  
Cation Exchange ◽  
Anion Exchange ◽  
Free Space ◽  
Cell Walls ◽  
Cation Exchange Capacity ◽  
Dry Weight ◽  
Exchange Capacity ◽  
Anion Exchange Capacity ◽  
Anion Exclusion ◽  
Donnan Free Space

Isolated delignified cell walls from Sphagnum russowii Warnsdorf were incubated in various chloride salt solutions at neutral pH (pH 7 – 8), and ion sorption was measured directly by neutron activation analysis. The anion-exchange capacity was estimated to be 63 – 66 μequiv./g dry weight of wall material in the protonated form. The volume of the anion-exclusion space was 2.63 ± 0.21 (± SD, n = 3) and 1.65 ± 0.35 (± SD, n = 2) mL/g dry weight in NaCl and CaCl2, respectively. A novel approach to measure the Donnan free space is proposed: for walls equilibrated in a salt mixture containing 10 mequiv./L NaCl and 10 mequiv./L CaCl2, the Na+ ions can be considered "uncondensed" in the Manning sense. From the Donnan relationship for Na+ and Cl− ions in the internal and external phases, the Donnan free space was calculated to be 1.77 mL/g dry weight. Titrating walls from pH 2.1 to 9.1 in the presence of 10 mequiv./L NaCl and 10 mequiv./L CaCl2 revealed a maximum cation-exchange capacity above pH 6 of ca. 1900 μequiv./g dry weight. This corresponds to a fixed anionic charge concentration in the Donnan free space of 1.1 M. Key words: ion exchange, cell wall, Donnan free space.

scholarly journals Effects of Zn and Cd accumulation on structural and physiological characteristics of barley plants

2007 ◽  
Vol 19 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Balaji B. Maruthi Sridhar ◽  
Fengxiang X. Han ◽  
Susan V. Diehl ◽  
David L. Monts ◽  
Yi Su
Keyword(s):  
Structural Changes ◽  
Metal Accumulation ◽  
Morphological Changes ◽  
Dry Weight ◽  
Vascular Bundles ◽  
Fresh Weight ◽  
Intercellular Spaces ◽  
Cd Accumulation ◽  
Potted Plants ◽  
High Concentrations

The objectives of this study were to identify the structural changes caused by Zn and Cd accumulation in shoots and roots of barley (Hordeum vulgare) plants; and to correlate metal accumulation with anatomical, physiological and morphological changes. Potted plants were exposed to metal treatments of Zn and Cd for 19 and 16 d respectively. Leaves, stems and roots were harvested to identify structural changes and analyze metal accumulation. Barley effectively accumulated Zn (up to 11283 mg kg-1) and Cd (up to 584 mg kg-1) in the shoots. Microscopic structural changes, such as a decrease in intercellular spaces, breakdown of vascular bundles, and shrinkage of palisade and epidermal cells, occurred in leaves, stems and roots of plants treated with high concentrations of Zn. Zinc accumulation also resulted in a significant decrease in water content, fresh weight, dry weight and plant height. Cadmium only caused structural changes in roots at the higher concentrations. Barley plants were able to accumulate significant amounts of Zn and Cd without exhibiting symptoms of phytotoxicity when the metal concentrations were relatively low.

scholarly journals Metabolite Profile of Xylem Sap in Cotton Seedlings Is Changed by K Deficiency

2020 ◽  
Vol 11 ◽  
Author(s):  
Xin Zhang ◽  
Guo Wang ◽  
Huiyun Xue ◽  
Jinbao Zhang ◽  
Qinglian Wang ◽  
...  
Keyword(s):  
High Performance ◽  
Xylem Sap ◽  
Dry Weight ◽  
Metabolite Profile ◽  
Root Surface ◽  
Mineral Nutrient ◽  
Root Surface Area ◽  
Nutrient Contents ◽  
Kegg Pathways ◽  
K Deficiency

Xylem sap, belonging to the plant apoplast, not only provides plant tissues with inorganic and organic substances but also facilitates communication between the roots and the leaves and coordinates their development. This study investigated the effects of potassium (K) deficiency on the morphology and the physiology of cotton seedlings as well as pH, mineral nutrient contents, and metabolites of xylem sap. In particular, we compared changes in root–shoot communication under low K (LK) and normal K (NK, control) levels. Compared to control, LK stress significantly decreased seedling biomass (leaf, stem, and root dry weight; stem and root length; root surface area and root volume) and the levels of K, Na (sodium), Mg (magnesium), Fe (iron), and Zn (zinc) in xylem sap. A total of 82 metabolites in sap analyzed by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) showed significant differences between the two conditions; among these, 38 were up-regulated more than 2-fold, while the others were down-regulated less than 0.5-fold. In particular, several metabolites found in the cell membrane including three cholines (glycerophosphatecholine, 2-hexenylcholine, and caproylcholine) and desglucocoroloside and others such as malondialdehyde, α-amino acids and derivatives, sucrose, and sugar alcohol significantly increased under LK stress, indicating that cell membranes were damaged and protein metabolism was abnormal. It is worth noting that glycerophosphocholine was up-regulated 29-fold under LK stress, indicating that it can be used as an important signal of root–shoot communication. Furthermore, in pathway analyses, 26 metabolites were matched to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways; L-aspartic acid, which was associated with 10 KEGG pathways, was the most involved metabolite. Overall, K deficiency reduced the antioxidant capacity of cotton seedlings and led to a metabolic disorder including elevated levels of primary metabolites and inhibited production of secondary metabolites. This eventually resulted in decreased biomass of cotton seedlings under LK stress. This study lays a solid foundation for further research on targeted metabolites and signal substances in the xylem sap of cotton plants exposed to K deficiency.

Differences in Water Relations Parameters for the Chlorenchyma and the Parenchyma of Opuntia ficus-indica Under Wet Versus Dry Conditions

1991 ◽  
Vol 18 (2) ◽  
pp. 95 ◽  
Author(s):  
G Goldstein ◽  
JL Andrade ◽  
PS Nobel
Keyword(s):  
Osmotic Pressure ◽  
Water Relations ◽  
Water Storage ◽  
Dry Weight ◽  
High Water ◽  
Opuntia Ficus Indica ◽  
Large Numbers ◽  
Parenchyma Cells ◽  
Storage Parenchyma ◽  
Dry Conditions

Water relations of the photosynthetic tissue (chlorenchyma) and of the water-storage parenchyma were studied for well watered and droughted Opuntia ficus-indica, a crassulacean acid metabolism plant cultivated worldwide for its fruits and cladodes. For well watered plants, die1 changes in osmotic pressure were evident in the chlorenchyma. Droughting the plants for 4 months resulted in a massive loss of water from the cladodes, particularly from the water-storage parenchyma, which could lose up to 82% of the water present at full turgor without irreversible tissue damage. Pressure-volume curves indicated a decrease in the osmotic pressure at full turgor of about 0.1 MPa for the water-storage parenchyma cells during drought; such a decrease of osmotically active solutes was consistent with the appearance of large numbers of starch grains. The bulk modulus of elasticity was 0.36 MPa for the water-storage parenchyma cells and 2.5-fold higher for the chlorenchyma cells, which were smaller with thicker cell walls than the former cells. Mucilage, a polysaccharide occurring extracellularly, constituted about 14% of the cladode dry weight; it could hold more than 30% of the total water content of the water-storage parenchyma. Polymerisation of sugars, large elastic cells in the water-storage parenchyma and mucilage with its high water-holding capacity helped maintain a positive turgor in the photosynthetic tissue, even after 4 months of drought.

Cellular pathways of source leaf phloem loading and phloem unloading in developing stems of Sorghum bicolor in relation to stem sucrose storage

2015 ◽  
Vol 42 (10) ◽  
pp. 957 ◽  
Author(s):  
Ricky J. Milne ◽  
Christina E. Offler ◽  
John W. Patrick ◽  
Christopher P. L. Grof
Keyword(s):  
Sorghum Bicolor ◽  
Cell Walls ◽  
Phloem Loading ◽  
Vascular Bundles ◽  
Phloem Unloading ◽  
Parenchyma Cells ◽  
Storage Parenchyma ◽  
Sucrose Storage ◽  
Cellular Pathways ◽  
And Storage

Cellular pathways of phloem loading in source leaves and phloem unloading in stems of sweet Sorghum bicolor (L.) Moench were deduced from histochemical determinations of cell wall composition and from the relative radial mobilities of fluorescent tracer dyes exiting vascular pipelines. The cell walls of small vascular bundles in source leaves, the predicted site of phloem loading, contained minimal quantities of lignin and suberin. A phloem-loaded symplasmic tracer, carboxyfluorescein, was retained within the collection phloem, indicating symplasmic isolation. Together, these findings suggested that phloem loading in source leaves occurs apoplasmically. Lignin was restricted to the walls of protoxylem elements located in meristematic, elongating and recently elongated regions of the stem. The apoplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moved radially from the transpiration stream, consistent with phloem and storage parenchyma cells being interconnected by an apoplasmic pathway. The major phase of sucrose accumulation in mature stems coincided with heavy lignification and suberisation of sclerenchyma sheath cell walls restricting apoplasmic tracer movement from the phloem to storage parenchyma apoplasms. Phloem unloading at this stage of stem development followed a symplasmic route linking sieve elements and storage parenchyma cells, as confirmed by the phloem-delivered symplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moving radially from the stem phloem.

Temporal and spatial expression of hexose transporters in developing tomato (Lycopersicon esculentum) fruit

2005 ◽  
Vol 32 (9) ◽  
pp. 777 ◽  
Author(s):  
Stephen J. Dibley ◽  
Michael L. Gear ◽  
Xiao Yang ◽  
Elke G. Rosche ◽  
Christina E. Offler ◽  
...  
Keyword(s):  
Lycopersicon Esculentum ◽  
Fruit Ripening ◽  
Tomato Fruit ◽  
Vascular Bundles ◽  
Hexose Transporter ◽  
Transporter Protein ◽  
Protein Levels ◽  
Parenchyma Cells ◽  
Storage Parenchyma ◽  
Post Transcriptional Regulation

Correlative physiological evidence suggests that membrane transport into storage parenchyma cells is a key step in determining hexose levels accumulated in tomato (Lycopersicon esculentum Mill.) fruit (Ruan et al. 1997). Expression of three previously identified hexose transporter genes (LeHT1, 2 and 3) demonstrated that LeHT3, and to a lesser extent LeHT1, are the predominant transporters expressed in young fruit (10 d after anthesis; DAA). Expression of both transporters dropped sharply until 24 DAA, after which only LeHT3 expression remained at detectable levels through to fruit ripening. LeHT2 was not expressed substantially until the onset of fruit ripening. For fruit at both 10 and 30 DAA, LeHT3 transcripts were detected in storage parenchyma cells of the outer pericarp tissue, but not in vascular bundles or the first layer of parenchyma cells surrounding these bundles. In contrast to LeHT gene expression, hexose transporter protein levels were maximal between 20 and 30 DAA, which corresponded to the period of highest hexose accumulation. The delayed appearance of transporter protein is consistent with some form of post-transcriptional regulation. Based on these analyses, LeHT3 appears to be responsible for the rapid hexose accumulation in developing tomato fruit.

The effects of amino acids on the growth and sporulation of Verticillium dahliae

1987 ◽  
Vol 65 (7) ◽  
pp. 1299-1302 ◽  
Author(s):  
D. R. Duncan ◽  
E. B. Himelick
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Acer Saccharum ◽  
Sugar Maple ◽  
Xylem Sap ◽  
Amino Acid Content ◽  
Fungal Growth ◽  
Dry Weight

Conidial and dry weight production of Verticillium dahliae varied greatly depending on the amino acid used as the nitrogen source in Czapek's–Dox medium. Variable fungal growth was also noted when mixtures of amino acids were used and growth was dependent on the type and concentration of each amino acid in the mixture. Similar variation was obtained when sugar maple (Acer saccharum) sap was amended with individual amino acids. These results are examined in relation to the reported variation in the amino acid content of host xylem sap and in relation to verticillium wilt development.

scholarly journals The Physiology of Sugar-Cane III. Characteristics of Sugar Uptake in Slices of Mature and Immature Storage Tissue

1960 ◽  
Vol 13 (3) ◽  
pp. 203 ◽  
Author(s):  
RL Bieleski
Keyword(s):  
Sugar Cane ◽  
Free Space ◽  
Sugar Concentration ◽  
Sugar Uptake ◽  
Accumulation Process ◽  
Anaerobic Conditions ◽  
Storage Tissue ◽  
Constant Rate ◽  
Two Stages ◽  
Initial Uptake

Sugar uptake by slices of sugar-cane storage tissue took place in two stages. The initial uptake reached an equilibrium within 1 hr, the level being proportional to the external sugar concentration, independent of the sugar, and unaffected by anaerobic conditions. This sugar diffused out rapidly when the tissue was placed in water. It was thus contained in the apparent free space, 10-20 per cent. of the tissue volume. The secondary uptake continued up to 60 hr at a slow, constant rate, 1-5 mgjgjday, independent of sugar concentration above 2� 0 per cent., dependent on the sugar, and inhibited by anaerobic conditions. This sugar did not diffuse out when the tissue was placed in water. It was concluded that the secondary uptake was an active accumulation process.

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