Aspects arising from the use of inhibitors in phloem transport studies

1980 ◽  
Vol 58 (7) ◽  
pp. 816-820 ◽  
Author(s):  
Johannes Willenbrink
Keyword(s):  
Carbon Metabolism ◽  
Cell Membranes ◽  
Cytochalasin B ◽  
Potassium Cyanide ◽  
Phloem Transport ◽  
Vascular Bundles ◽  
Pelargonium Zonale ◽  
Transport Studies ◽  
Central Bundle ◽  
Sugar Phosphates

Experiments on the movement of 14C-assimilates through dissected vascular bundles of Pelargonium zonale are reviewed. Potassium cyanide (KCN) applied to the central bundle causes localized, reversible blockage of transport. Both antimycin and atractylate, but not ouabain inhibit the movement of metabolites through the phloem. The proton ionophore, CCCP completely suppresses translocation at 10−7 M, however, cell membranes are damaged. Valinomycin applied to cut bundles causes serious disturbances in carbon metabolism as shown by the increased label in sugar phosphates. Cytochalasin B does not affect translocation. Limitations on conclusions drawn from inhibitor studies are discussed.

scholarly journals Abscisic acid as a factor in regulation of photosynthetic carbon metabolism of pea seedlings

2014 ◽  
Vol 51 (2) ◽  
pp. 229-240 ◽  
Author(s):  
Maria Faltynowicz ◽  
Waldemar Lechowicz ◽  
Jerzy Poskuta
Keyword(s):  
Abscisic Acid ◽  
Carbon Metabolism ◽  
Rubp Carboxylase ◽  
Pep Carboxylase ◽  
Pea Seedlings ◽  
Photosynthetic Carbon ◽  
Photosynthetic Carbon Metabolism ◽  
Sugar Phosphates ◽  
Reduced Activity ◽  
Endogenous Aba

The influence of abscisic acid (ABA) on carbon metabolism and the activity of ribulosebisphosphate (RuBP) and phosphoenolpyruvate (PEP) carboxylases in 8-day-old pea seedlings was investigated. It was endeavoured to correlate the changes observed in metabolic processes with the endogenous ABA level. In plants treated with ABA incorporation of labeled carbon into sucrose, glucose, fructose and sugar phosphates was depressed, while <sup>14</sup>C incorporation into starch, ribulose and malic acid was enhanced. The activity of RuBP carboxylase was considerably lowered, whereas that of PEP carboxylase was slightly increased. It is considered that inhibition of photosynthesis due to the action of ABA is caused to a great extent by the obstruction of the C-3 pathway and reduced activity of RuBP carboxylase, whereas (β-carboxylation was not blocked.

scholarly journals Phloem Transport Velocity Varies over Time and among Vascular Bundles during Early Cucumber Seedling Development

2013 ◽  
Vol 163 (3) ◽  
pp. 1409-1418 ◽  
Author(s):  
Jessica A. Savage ◽  
Maciej A. Zwieniecki ◽  
N. Michele Holbrook
Keyword(s):  
Phloem Transport ◽  
Seedling Development ◽  
Vascular Bundles ◽  
Cucumber Seedling ◽  
Transport Velocity ◽  
Over Time

The extraction of photosynthate high in [11C]sucrose and its translocation in sunflower stems

1980 ◽  
Vol 58 (1) ◽  
pp. 100-107 ◽  
Author(s):  
D. B. Hayden ◽  
D. S. Fensom ◽  
R. G. Thompson
Keyword(s):  
Half Life ◽  
Indirect Evidence ◽  
Phloem Transport ◽  
Water Soluble ◽  
Vascular Bundles ◽  
Soluble Extract ◽  
Xylem Transport ◽  
Phloem Translocation ◽  
Water Soluble Extract ◽  
The Individual

A technique has been developed to biosynthesize a water-soluble extract of 11C-labelled photosynthate high in [11C]sucrose. The extract can be produced in less than 1 half-life (20 min) and is of high activity. When 11C-labelled extract was fed to the individual vascular bundles of other living plants, 11C was taken up and translocated, and on the basis of direct and indirect evidence it was largely in the form of [11C]sucrose.11C-labelled extract, if fed to a flap or gentle scraping on the surface of a sunflower stem (or corn, cow-parsnip, pine, or elm) was translocated both apically and basally from the feed point. Incisions into xylem vessels produced very rapid tracer movements which seemed to be associated with xylem vessel liquid cavitation and also transpiration pull. Shallower cuts produced translocation patterns similar to 11CO2 leaf feedings and are thought to be largely in the phloem. Phloem transport was blocked by ice chilling; xylem transport was only slightly affected by ice, if at all. Phloem translocation profiles often displayed steps at the front of mass flow, and later appeared to have peaks of activity moving along them. The movements were sometimes rapid (>6 cm min−1) and appeared to be complex, as if different channels were conducting at different speeds in parallel.

scholarly journals The tissue structure of the vegetative organs of strawberry (Fragaria moschata Duch®)

2000 ◽  
Vol 6 (1) ◽  
Author(s):  
J. Papp ◽  
I. Lenkefi ◽  
M. Gara ◽  
P. Gracza
Keyword(s):  
Tissue Structure ◽  
Vascular Bundles ◽  
Root Structure ◽  
Lower Epidermis ◽  
Palisade Parenchyma ◽  
Vegetative Organs ◽  
Ring Shape ◽  
Central Bundle ◽  
Upper Third

The tissue structure of the vegetative organs of strawberry (root, rhizome, stolon, leaf) is discussed in this paper. The authors stated that the root structure described by Muromcev (1969) and Naumann-Seip (1989) develops further from the primary structure. It grows secondarily and the transport tissue becomes continuous having ring shape. In the primary cortex of the rhizome periderm like tissue differentiates, but according to the examinations up to now, it does not take over the role of the exodermis. The exodermis is phloboran filled primary cortex tissue with 3-4 cell rows under the rhizodermis. The development of the transport tissue of the petiole is also a new recognition. In the lower third of the petiole the transport tissue consists of 3 collaterally compound vascular bundles. In the middle third there are 5 bundles because of the separation of the central bundle and in the upper third of the petiole 7 bundles can be observed because of the ramification of the outside bundles. Therefore attention must be taken also in the case of other plants at making sections. There might be confusions in the results of the examinations if the number of bundles increases in the petiole. The tissue structure might vary depending on the origin of the tissue segment. The palisade parenchyma of the leaf blade has two layers and it is wider than the spongy parenchyma. Among the 5-6-angular cells of the upper epidermis do not develop stomata while in the lower epidermis there are a fairly lot of them.

Transport of Metabolites between the Mesophyll and Epidermis of Commelina cyanea R. Br.

1984 ◽  
Vol 11 (2) ◽  
pp. 59
Author(s):  
N Thorpe ◽  
F.L Milthorpe
Keyword(s):  
Guard Cell ◽  
Cell Membranes ◽  
Net Photosynthesis ◽  
Initial Values ◽  
Sugar Phosphates ◽  
Net Fluxes

The concentrations of 10 major metabolites in the epidermis were one-third to one-half of those in the mesophyll when the stomata were open. I4CO2 was supplied to the leaf and the radioactivity contained in glucose, sucrose, sugar phosphates, malate, glycine, serine and alanine, and the ethanolinsoluble HC1-hydrolysable fraction was followed for 2 h in both the mesophyll and epidermis. The net fluxes from mesophyll to epidermis were in the range 0.7-4 nmol m-2 s-I when the leaf was actively photosynthesizing and fell to near zero or became negative with no net photosynthesis. Fluxes were largely independent of concentration differences, which did not vary greatly from initial values. Although the amounts reaching the epidermis greatly exceeded those fixed from C02 in situ, available evidence suggests that the epidermis may have the capacity to supply its own carbon needs; the carbon imported no doubt supplies extra substrates and energy and may influence the flux of K+ ions through the guard-cell membranes. Efflux curves indicated that one-half to three-quarters of the soluble substances in the epidermis diffused readily from it but only about 10% of those in the mesophyll diffused rapidly.

scholarly journals Ionic channels in plants: potassium transport

1995 ◽  
Vol 25 (1) ◽  
pp. 173-176
Author(s):  
Antonio Costa de Oliveira
Keyword(s):  
Growth And Development ◽  
Ionic Channels ◽  
Phloem Transport ◽  
Potassium Transport ◽  
Plant Growth And Development ◽  
Nutrient Storage ◽  
Transport Studies ◽  
Transport Regulation ◽  
Leaf Movements ◽  
External Signals

The discovery of potassium channels on the plasma membrane has helped to elucidate important mechanisms in animal and plant physiology. Plant growth and development associated mechanisms, such as germination, leaf movements, stomatal action, ion uptake in roots, phloem transport and nutrient storage are linked to potassium transport. Studies describing potassium transport regulation by abscisic acid (ABA), Ca++, light and other factors are presented here. Also the types of channels that regulate potassium uptake and efflux in the cell, and the interaction of these channels with external signals, are discussed.

scholarly journals The consequences of lipid remodelling of adipocyte cell membranes being functionally distinct from global lipid storage during obesity

2019 ◽  
Author(s):  
Ke-di Liu ◽  
Animesh Acharjee ◽  
Christine Hinz ◽  
Sonia Liggi ◽  
Antonio Murgia ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
White Adipose Tissue ◽  
Carbon Metabolism ◽  
Cell Membranes ◽  
Solid Phase ◽  
Mass Composition ◽  
Methylation Of Dna ◽  
Adipocyte Cell ◽  
One Carbon Metabolism ◽  
Body Mass Composition

AbstractObesity is a complex disorder where the genome interacts with diet and environmental factors to ultimately influence body mass, composition and shape. Numerous studies have investigated how bulk lipid metabolism of adipose tissue changes with obesity, and in particular how the composition of triglycerides (TGs) changes with increased adipocyte expansion. However, reflecting the analytical challenge posed by examining non-TG lipids in extracts dominated by TGs, the glycerophospholipid (PL) composition of cell membranes has been seldom investigated. PLs contribute to a variety of cellular processes including maintaining organelle functionality, providing an optimised environment for membrane-associated proteins and as pools for metabolites (e.g. choline for one-carbon metabolism and for methylation of DNA). We have conducted a comprehensive lipidomic study of white adipose tissue in mice who become obese either through genetic modification (ob/ob), diet (high fat diet) or a combination of the two using both solid phase extraction and ion mobility to increase coverage of the lipidome. Composition changes in seven classes of lipid (free fatty acids, diglycerides, TGs, phosphatidylcholines, lyso-phosphatidylcholines, phosphatidylethanolamines, and phosphatidylserines) correlated with perturbations in one-carbon metabolism and transcriptional changes in adipose tissue. We demonstrate that changes in TGs that dominate the overall lipid composition of white adipose tissue are distinct from diet-induced alterations of PLs, the predominant components of the cell membranes. PLs correlate better with transcriptional and one-carbon metabolism changes within the cell, suggesting the compositional changes that occur in cell membranes during adipocyte expansion have far-reaching functional consequences.

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