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- Carbon partitioning (3)
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- Phloem loading (1)
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Articles 31 - 60 of 76
Full-Text Articles in Biology
Role Of Free Space In Translocation In Sugar Beet, Donald Geiger, Susan Sovonick, Terri Shock, Robert Fellows
Role Of Free Space In Translocation In Sugar Beet, Donald Geiger, Susan Sovonick, Terri Shock, Robert Fellows
Donald R. Geiger
The involvement of the free space in phloem loading of sucrose was studied in sugar beet source leaves (Beta vulgaris, L.). Sucrose, supplied exogenously to the abraded upper surface of leaves at a concentration of 20 mM, was available for translocation at rates similar to those obtained with photosynthesis. The exogenous sucrose substituted as a source of translocate for assimilate derived from photosynthesis when the latter process was disrupted by plasmolysis of the leaf with 0.8 M mannitol. The mesophyll symplast was not completely disrupted by this treatment, however. Data from the sugar uptake experiments indicate that phloem loading can …
Effects Of Translocation And Assimilate Demand On Photosynthesis, Donald Geiger
Effects Of Translocation And Assimilate Demand On Photosynthesis, Donald Geiger
Donald R. Geiger
Net carbon dioxide uptake by a photosynthesizing primary leaf of bean plants, Phaseolus vulgaris cv. Black Valentine, was measured during treatments designed to alter export from the leaf. Removal of shoot apices lessened sink demand while removal of all source leaves except the one being observed increased sink demand. Export from the leaf under study was lessened by chilling the primary leaf petiole and node to 2 °C. No adjustments in the rate of net photosynthesis were observed during the 33-h period after any of the treatments. The results of this study are in general agreement with previous reports in …
Mechanism Of Cyanide Inhibition Of Phloem Translocation, Robert Giaquinta, Donald Geiger
Mechanism Of Cyanide Inhibition Of Phloem Translocation, Robert Giaquinta, Donald Geiger
Donald R. Geiger
Petiolar application of potassium cyanide inhibited 14C-assimilate translocation without affecting source leaf photosynthesis or phloem loading of sucrose inPhaseolus vulgaris. The inhibition of transport was correlated with disruption of the structural integrity of the sieve tubes (sieve pore blockage) rather than impairment of a metabolic process in the translocation path driving translocation.
Evidence For Active Phloem Loading In The Minor Veins Of Sugar Beet, Susan Sovonick, Donald Geiger, Robert Fellows
Evidence For Active Phloem Loading In The Minor Veins Of Sugar Beet, Susan Sovonick, Donald Geiger, Robert Fellows
Donald R. Geiger
Phloem loading in source leaves of sugar beet (Beta vulgaris, L.) was studied to determine the extent of dependence on energy metabolism and the involvement of a carrier system. Dinitrophenol at a concentration of 4 mM uncoupled respiration, lowered source leaf ATP to approximately 40% of the level in the control leaf and inhibited translocation of exogenously supplied 14C-sucrose to approximately 20% of the control. Dinitrophenol at a concentration of 8 mM inhibited rather than promoted CO2 production, indicating a mechanism of inhibition other than uncoupling of respiration. The 8 mM dinitrophenol also reduced ATP to approximately 40% of the …
Solute Distribution In Sugar Beet Leaves In Relation To Phloem Loading And Translocation, Donald Geiger, Robert Giaquinta, Susan Sovonick, Robert Fellows
Solute Distribution In Sugar Beet Leaves In Relation To Phloem Loading And Translocation, Donald Geiger, Robert Giaquinta, Susan Sovonick, Robert Fellows
Donald R. Geiger
The distribution of solutes in the various cells of sugar beet (Beta vulgaris L.) source leaves, petioles, and sink leaves was studied in tissue prepared by freeze-substitution. The differences in degree of cryoprotection indicated that sieve elements and companion cells of the source leaf, petiole, and sink leaf contain a high concentration of solute. The osmotic pressure of various types of cells was measured by observing incipient plasmolysis in freeze-substituted tissues equilibrated with a series of mannitol solutions prior to rapid freezing. Analysis of source leaf tissue revealed osmotic pressure values of 13 bars for the mesophyll and 30 bars …
Diurnal Regulation Of Photosynthetic Carbon Metabolism In C3 Plants, Donald Geiger, Jerome Servaites
Diurnal Regulation Of Photosynthetic Carbon Metabolism In C3 Plants, Donald Geiger, Jerome Servaites
Donald R. Geiger
No abstract provided.
Measurement Of Translocation, Donald Geiger
A Method For Calculating Sucrose Synthesis Rates Throughout A Light Period In Sugar Beet Leaves, Donald Geiger, Bernadette Fondy, Michelle Tucci
A Method For Calculating Sucrose Synthesis Rates Throughout A Light Period In Sugar Beet Leaves, Donald Geiger, Bernadette Fondy, Michelle Tucci
Donald R. Geiger
Sucrose synthesis rate in an exporting sugar beet (Beta vulgaris L.) leaf was calculated from simultaneous measurements of export and changes in leaf sucrose level. The amount of recently fixed carbon exported was determined from net carbon assimilated minus the tracer carbon accumulated in the leaf. The relative amount of 14C accumulated in the leaf supplied with 14CO2 throughout an entire light period was recorded continuously with a Geiger-Mueller detector. To produce a continuous time course for tracer carbon accumulated in the leaf during the light period, the latter curve was superimposed on values for tracer carbon accumulated in leaves …
Leaf Carbon Metabolism And Metabolite Levels During A Period Of Sinusoidal Light, Jerome Servaites, Donald Geiger, Michelle Tucci, Bernadette Fondy
Leaf Carbon Metabolism And Metabolite Levels During A Period Of Sinusoidal Light, Jerome Servaites, Donald Geiger, Michelle Tucci, Bernadette Fondy
Donald R. Geiger
Photosynthesis rate, internal CO2 concentration, starch, sucrose, and metabolite levels were measured in leaves of sugar beet (Beta vulgaris L.) during a 14-h period of sinusoidal light, which simulated a natural light period. Photosynthesis rate closely followed increasing and Dec.reasing light level. Chloroplast metabolite levels changed in a manner indicating differential activation of enzymes at different light levels. Starch levels Dec.lined during the first and last 2 hours of the photoperiod, but increased when photosynthesis rate was greater than 50% of maximal. Sucrose and sucrose phosphate synthase levels were constant during the photoperiod, which is consistent with a relatively steady …
Identification, Purification, And Molecular Cloning Of A Putative Plastidic Glucose Translocator, Andreas Weber, Jerome Servaites, Heike Kofler, Diana Hille, Ferdi Gröner, Donald Geiger, Ulrike Hebbeker, Ulf-Ingo Flüggea
Identification, Purification, And Molecular Cloning Of A Putative Plastidic Glucose Translocator, Andreas Weber, Jerome Servaites, Heike Kofler, Diana Hille, Ferdi Gröner, Donald Geiger, Ulrike Hebbeker, Ulf-Ingo Flüggea
Donald R. Geiger
During photosynthesis, part of the fixed carbon is directed into the synthesis of transitory starch, which serves as an intermediate carbon storage facility in chloroplasts. This transitory starch is mobilized during the night. Increasing evidence indicates that the main route of starch breakdown proceeds by way of hydrolytic enzymes and results in glucose formation. This pathway requires a glucose translocator to mediate the export of glucose from the chloroplasts. We have reexamined the kinetic properties of the plastidic glucose translocator and, using a differential labeling procedure, have identified the glucose translocator as a component of the inner envelope membrane. Peptide …
Phloem Loading In Source Leaves, Donald Geiger
Uptake And Distribution Of N-Phosphonomethylglycine In Sugar Beet Plants, Judy Gougler, Donald Geiger
Uptake And Distribution Of N-Phosphonomethylglycine In Sugar Beet Plants, Judy Gougler, Donald Geiger
Donald R. Geiger
Glyphosate (N-phosphonomethylglycine) was readily transported in sugar beet plants (Beta vulgaris L., Klein E type, monogerm). Concentrations in sink leaves reached 2.5 to 13.7 micromolar in 10 hours from a 15 millimolar solution supplied to one mature leaf. Distribution of glyphosate followed that of [3H]sucrose used as a marker for materials transported by phloem, indicating that this is the primary means for distribution of glyphosate. Possible mechanisms of entry into the sieve tubes were evaluated using isolated leaf discs. Concentration dependence of uptake and kinetics of exodiffusion from tissue indicate a passive, nonfacilitated mechanism. Uptake was not affected by pH, …
Germination Of Australian Channel Millet (Echinochloa Turnerana (Domin) J.M. Black) Seeds. I. Dormancy In Relation To Light And Water, Denis Conover, Donald Geiger
Germination Of Australian Channel Millet (Echinochloa Turnerana (Domin) J.M. Black) Seeds. I. Dormancy In Relation To Light And Water, Denis Conover, Donald Geiger
Donald R. Geiger
Channel millet, a native to inland Australia, is recognized as a promising forage and grain crop for arid regions. In its native habitat germination occurs after the flood plains are inundated. Newly harvested seeds were dormant, but germinated after several months of storage or after disruption of enclosing structures. Intact, after-ripened seeds did not germinate in the dark, but dehulled seeds achieved high percentage germination in the dark. Secondary dormancy was induced by imbibing intact seeds in the dark and was broken by subsequent dry storage or by disruption of enclosing structures. Intact, after-ripened seeds that were subjected to wetting-drying …
Effects Of Light Intensity And Oxygen On Photosynthesis And Translocation In Sugar Beet, Donald Geiger, Jerome Servaites
Effects Of Light Intensity And Oxygen On Photosynthesis And Translocation In Sugar Beet, Donald Geiger, Jerome Servaites
Donald R. Geiger
The mass transfer rate of 14C-sucrose translocation from sugar beet (Beta vulgaris, L.) leaves was measured over a range of net photosynthesis rates from 0 to 60 milligrams of CO2 Dec.imeters−2 hour−1 under varying conditions of light intensity, CO2 concentration, and O2 concentration. The resulting rate of translocation of labeled photosynthate into total sink tissue was a linear function (slope = 0.18) of the net photosynthesis rate of the source leaf regardless of light intensity (2000, 3700, or 7200 foot-candles), O2 concentration (21% or 1% O2), or CO2 concentration (900 microliters/liter of CO2 to compensation concentration). These data support the …
Glyphosate Effects On Carbon Assimilation, Ribulose Bisphosphate Carboxylase Activity, And Metabolite Levels In Sugar Beet Leaves, Jerome Servaites, Michelle Tucci, Donald Geiger
Glyphosate Effects On Carbon Assimilation, Ribulose Bisphosphate Carboxylase Activity, And Metabolite Levels In Sugar Beet Leaves, Jerome Servaites, Michelle Tucci, Donald Geiger
Donald R. Geiger
Application of a 17-millimolar solution of glyphosate (GLP) to sugarbeet (Beta vulgaris L.) leaves resulted in an immediate and rapid Dec.line in the level of ribulose bisphosphate (RuBP). Phosphoglyceric acid level began to Dec.rease about 2 hours following the Dec.line in RuBP level. Photosynthesis rate Dec.lined linearly with RuBP level, but only when the RuBP level had Dec.reased to about twice the RuBP carboxylase active site concentration. This occurred about 4 hours following GLP-application. At this time starch synthesis also Dec.lined abruptly. The activation state of RuBP carboxylase did not change for 8 hours following GLP application and then Dec.reased …
Sources Of Sucrose Translocated From Illuminated Sugar Beet Source Leaves, Donald Geiger, Theodore Fox
Sources Of Sucrose Translocated From Illuminated Sugar Beet Source Leaves, Donald Geiger, Theodore Fox
Donald R. Geiger
A search for source leaf sucrose pools that differed in their relation to export was carried out in photosynthesizing leaves of Beta vulgaris L. The time course of depletion of [14C]sucrose in a leaf in unlabeled CO2 following steady state labeling provided evidence for two distinct sucrose pools. After the start of the light period, leaf blade sucrose remained constant although it exchanged between the two pools. Newly synthesized sucrose destined for export passed through one pool more rapidly than through the other. All of the leaf blade sucrose appeared to exchange with export sucrose. Modeling and regression analysis of …
Potassium Nutrition And Translocation In Sugar Beet, Terrance Conti, Donald Geiger
Potassium Nutrition And Translocation In Sugar Beet, Terrance Conti, Donald Geiger
Donald R. Geiger
The effect of increased net foliar K+ accumulation on translocation of carbon was studied in sugar beet (Beta vulgaris, L. var. Klein E and US H20) plants. Net accumulation of recently absorbed K+ was studied by observing arrival of 42K+per unit area of leaf. Labeled K+ was added to give an initial concentration at 2 or 10 millimolar K+ in mineral nutrient solution. Because the newly arrived K+constitutes a small part of the total leaf K+ in plants raised in 10 millimolar K+, export of 42K+ by phloem was negligible over the 2- to 3-day period; consequently, accumulation is a …
Distribution Of Imported Glyphosate In Quackgrass (Elytrigia Repens) Rhizomes In Relation To Assimilate Accumulation, Wen-Jang Shieh, Donald Geiger, Stephen Buczynski
Distribution Of Imported Glyphosate In Quackgrass (Elytrigia Repens) Rhizomes In Relation To Assimilate Accumulation, Wen-Jang Shieh, Donald Geiger, Stephen Buczynski
Donald R. Geiger
The fact that quackgrass may occasionally escape control by the herbicide glyphosate is thought to result from the wide range in growth rate and sink activity among rhizome buds, especially in older portions of the rhizome. To study growth of rhizome structures, we supplied whole plants with ¹⁴CO₂ throughout a 10-h light period and determined the amount of labeled carbon accumulated by the end of the subsequent 14-h night. Growth of rhizome structures during this 24-h period was estimated by determining their growth rate coefficients: the amount of labeled carbon accumulated per unit of carbon present in the structure. Growth …
Osmotic Response Of Sugar Beet Source Leaves At Co2compensation Point, Theodore Fox, Donald Geiger
Osmotic Response Of Sugar Beet Source Leaves At Co2compensation Point, Theodore Fox, Donald Geiger
Donald R. Geiger
As sugar beet source leaves lowered the CO2 concentration to compensation point in a closed atmosphere, leaf thickness and relative water content Dec.reased. Leaf water potential Dec.lined rapidly from −0.5 to −1.4 megapascals. At 340 microliters CO2 per liter, water potential and sucrose, glucose, and fructose contents were steady in photosynthesizing source leaves. Within 90 minutes after leaves were exposed to a CO2 concentration at the compensation point, leaf sucrose content Dec.lined to 60% of the preteatment level, rapidly in the first 30 minutes and then more slowly. During the subsequent 200 minutes, sucrose content increased to 180% of pretreatment …
Phloem Unloading In Developing Leaves Of Sugar Beet: I. Evidence For Pathway Through The Symplast, J. Schmalstig, Judy Gougler, Donald Geiger
Phloem Unloading In Developing Leaves Of Sugar Beet: I. Evidence For Pathway Through The Symplast, J. Schmalstig, Judy Gougler, Donald Geiger
Donald R. Geiger
Physiological and transport data are presented in support of a symplastic pathway of phloem unloading in importing leaves of Beta vulgaris L. (`Klein E multigerm'). The sulfhydryl reagent p-chloromercuribenzene sulfonic acid (PCMBS) at concentration of 10 millimolar inhibited uptake of exogenous [14C]sucrose by sink leaf tissue over sucrose concentrations of 0.1 to 5.0 millimolar. Inhibited uptake was 24% of controls. The same PCMBS treatment did not affect import of14C-label into sink leaves during steady state labeling of a source leaf with14CO2. Lack of inhibition of import implies that sucrose did not pass through the free space during unloading. A passively …
Significance Of Carbon Allocation To Starch In Growth Of Beta Vulgaris, Brigette Fondy, Donald Geiger
Significance Of Carbon Allocation To Starch In Growth Of Beta Vulgaris, Brigette Fondy, Donald Geiger
Donald R. Geiger
No abstract provided.
Photosynthetic Carbon Metabolism And Translocation In Wild-Type And Starch-Deficient Mutant Nicotiana Sylvestris L, Donald Geiger, Wen-Jang Shieh, X. Yu
Photosynthetic Carbon Metabolism And Translocation In Wild-Type And Starch-Deficient Mutant Nicotiana Sylvestris L, Donald Geiger, Wen-Jang Shieh, X. Yu
Donald R. Geiger
A high rate of daytime export of assimilated carbon from leaves of a starch-deficient mutant tobacco (Nicotiana sylvestris L.) was found to be a key factor that enabled shoots to grow at rates comparable to those in wild-type plants under a 14-h light period. Much of the newly fixed carbon that would be used for starch synthesis in leaves of wild-type plants was used instead for sucrose synthesis in the mutant. As a result, export doubled and accumulation of sucrose and hexoses increased markedly during the day in leaves of the mutant plants. The increased rate of export to sink …
Effect Of Environmental Factors On Whole Plant Assimilate Partitioning And Associated Gene Expression, Donald Geiger, K. Koch, Wen-Jang Shieh
Effect Of Environmental Factors On Whole Plant Assimilate Partitioning And Associated Gene Expression, Donald Geiger, K. Koch, Wen-Jang Shieh
Donald R. Geiger
Partitioning of assimilated carbon among sink organs is a critical factor that controls the rate and pattern of plant growth. Time-course measurements of plant and organ growth rates are useful for determining how regulation of carbon partitioning controls plantgrowth. Measuring growth rates over a 24 h period reveals the current pattern of carbon partitioning that can be used to predict growth ratesof specific sinks. Comparison of growth rates among sinks under defined conditions can point out key factors that regulate partitioning ofrecently assimilated carbon among sinks. Internal control of carbonpartitioning by developmental programmes regulates the timing andsite of carbon distribution …
Germination Of Australian Channel Millet (Echinochloa Turnerana (Domin) J.M. Black) Seeds. Ii. Effects Of Anaerobic Conditions, Continuous Flooding, And Low Water Potential, Denis Conover, Donald Geiger
Germination Of Australian Channel Millet (Echinochloa Turnerana (Domin) J.M. Black) Seeds. Ii. Effects Of Anaerobic Conditions, Continuous Flooding, And Low Water Potential, Denis Conover, Donald Geiger
Donald R. Geiger
Channel millet seeds require a period of substantial wetting (as occurs during flooding) before mass germination is attained in its native environment, while the remainder of the life cycle often occurs under arid conditions. Imbibing seeds in solutions of mannitol or NaCl ranging from 0 to -1.5 MPa slowed germination and seedling growth but, after 14 days of imbibition in the light at 30°C germination was about 50% even at levels of moisture availability as low as -1.0 MPa. High germination percentages were also attained in the light inside flasks flushed continuously with humidified air, humidified N2, or N2 followed …
Analysing Partitioning Of Recently Fixed And Of Reserve Carbon In Reproductive Phaseolus Vulgaris L. Plants, Donald Geiger, Wen-Jang Shieh
Analysing Partitioning Of Recently Fixed And Of Reserve Carbon In Reproductive Phaseolus Vulgaris L. Plants, Donald Geiger, Wen-Jang Shieh
Donald R. Geiger
Partitioning of recently-fixed carbon among plant organs and subsequent distribution of reserve carbon were studied by supplying whole shoots of bean plants (Phaseolus vulgaris L.) with 14C-labelled CO2 of constant specific radioactivity throughout a photoperiod. The gain of tracer carbon in each part revealed net accumulation of recently-fixed carbon from direct fixation, import or both. Growth rate coefficients describing the present pattern of plant growth were calculated from ratios of tracer carbon to total carbon present in plant organs and were used to project future plant form. The period 10–20 d after the start of flowering was marked by a …
Sugar Transport In The Phloem: Demonstration Of Saturation Kinetics Of Phloem Loading And Transport Of Exogenous Sucrose, Donald Geiger, Susan Sovonick
Sugar Transport In The Phloem: Demonstration Of Saturation Kinetics Of Phloem Loading And Transport Of Exogenous Sucrose, Donald Geiger, Susan Sovonick
Donald R. Geiger
No abstract provided.
Mechanisms Of Glyphosate Toxicity In Velvetleaf (Abutilon Theophrasti Medikus), Mark Fuchs, Donald Geiger, Tracey Reynolds, June Bourque
Mechanisms Of Glyphosate Toxicity In Velvetleaf (Abutilon Theophrasti Medikus), Mark Fuchs, Donald Geiger, Tracey Reynolds, June Bourque
Donald R. Geiger
In velvetleaf source leaves, glyphosate caused gradual inhibition of photosynthesis that increased over several days and was nearly complete by five days. Gas exchange measurements revealed that a Dec.rease in stomatal conductance was a major factor in this reduction. Calvin cycle metabolite levels diminished along with photosynthesis rates but to a lesser extent than stomatal conductance, as indicated by the rise in water use efficiency and the lowering of internal leaf carbon dioxide. Though accumulation of shikimate confirmed that glyphosate was being taken up by the source leaves, this was insufficient to explain the lessened effect on photosynthesis. The protracted …
Translocation Of 14c Sucrose In Sugar Beet During Darkness, Donald Geiger, J. Batey
Translocation Of 14c Sucrose In Sugar Beet During Darkness, Donald Geiger, J. Batey
Donald R. Geiger
The time-course of arrival of 14C translocate in a sink leaf was studied in sugar beet (Beta vulgaris L. cultivar Klein Wanzleben) for up to 480 minutes of darkness. Following darkening of the source leaf, translocation rapidly Dec.lined, reaching a rate approximately 25% of the light period rate by 150 minutes. Comparison of data from plants that were girdled 1 cm below the crown with data from ungirdled plants indicates that after about 150 minutes darkness the beet root becomes a source of translocate to the sink leaf. After about 90 minutes darkness, starch-like reserve polysaccharide from the source leaf …
Effect Of Exogenously Supplied Foliar Potassium On Phloem Loading In Beta Vulgaris L., Donald Geiger, Diane Doman
Effect Of Exogenously Supplied Foliar Potassium On Phloem Loading In Beta Vulgaris L., Donald Geiger, Diane Doman
Donald R. Geiger
The effect of foliar application of K+ on processes associated with phloem loading was investigated in source leaves of sugar beet (Beta vulgaris L.). KCI was supplied exogenously at concentrations of up to 100 millimolar in the solution bathing the abraded upper epidermis of source leaves. K+ added at concentrations below 30 millimolar generally promoted the rate of export of material derived from 14CO2 but not from exogenously applied [14C]sucrose. Paralleling promotion of export, the level of material derived from photosynthesis, which was released into the bathing solution, also increased in response to addition of K+ to the free space. …
Diurnal Pattern Of Translocation And Carbohydrate Metabolism In Source Leaves Of Beta Vulgaris L., Bernadette Fondy, Donald Geiger
Diurnal Pattern Of Translocation And Carbohydrate Metabolism In Source Leaves Of Beta Vulgaris L., Bernadette Fondy, Donald Geiger
Donald R. Geiger
Transitions in carbohydrate metabolism and translocation rate were studied for evidence of control of export by the sugar beet (Beta vulgaris L. Klein E.) source leaf. Steady-state labeling was carried out for two consecutive 14-hour light periods and various quantities related to translocation were measured throughout two 24-hour periods. Starch accumulation following illumination was delayed. Near the end of the light period, starch stopped accumulating, whereas photosynthesis rate and sucrose level remained unchanged. At the beginning of the dark period there was a 75-minute delay before starch was mobilized. The rate of import to the developing sink leaves at night …