scholarly journals Nectar Production in Abutilon IV. Wate'r and Solute Relations

1971 ◽  
Vol 24 (3) ◽  
pp. 677 ◽  
Author(s):  
Nele Findlay ◽  
ML Reed ◽  
FV Mercer
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Sucrose Solution ◽  
Molar Concentration ◽  
Sugar Concentration ◽  
Nectar Production

Nectar secreted by isolated nectaries floated on sucrose solution was of a higher total molar concentration than the medium. However, under steady-state conditions, the 8ucrose concentration was lower than that of the medium, the nectar containing glucose and fructose in addition to sucrose_ When mannitol was added to the medium the osmotic pressure of the nectar exceeded that of the medium although the total molar sugar concentration of the nectar could be somewhat less

scholarly journals Nectar Production in Abutilon III. Sugar Secretion

1971 ◽  
Vol 24 (3) ◽  
pp. 665 ◽  
Author(s):  
Nele Findlay ◽  
ML Reed ◽  
FV Mercer
Keyword(s):  
Osmotic Pressure ◽  
External Medium ◽  
Sucrose Solution ◽  
Sucrose Concentration ◽  
Sugar Content ◽  
Total Sugar ◽  
Nectar Secretion ◽  
Nectar Production ◽  
Steady Rate ◽  
Two Phases

Analysis of Abutilon nectaries shows that the sugar content of the nectary rises sharply as nectar secretion begins. Nectar secretion on the plant occurs at a steady rate of 2-5 mg total sugar per flower. hour for 36-48 hr. A total of about 100 mg sugar per flower is secreted, and this is about seven times the maximum sugar content of the nectary at any time. Secretion of sugar in nectar by isolated nectaries floating on 0--0� 4M sucrose solution is in two phases. During phase I the rate is independent of concentration of sucrose in the external medium, but the rate is decreased by increasing the osmotic pressure of the medium with mannitol. In phase II the rate of secretion of sugar depends on the concentration of sucrose in the external medium and is independent of increase in osmotic pressure with mannitol. The rate is zero on water and reaches a maximum on about O� 4M sucrose. Secretion is reduced in both phases on media of sucrose concentration

scholarly journals Flower mites decrease nectar availability in the rain-forest bromeliad Neoregelia johannis

2010 ◽  
Vol 26 (4) ◽  
pp. 373-379 ◽  
Author(s):  
Tadeu J. Guerra ◽  
Gustavo Q. Romero ◽  
Woodruff W. Benson
Keyword(s):  
Rain Forest ◽  
Sugar Content ◽  
Sugar Concentration ◽  
Production Rates ◽  
Nectar Production ◽  
Nectar Volume ◽  
Bombus Morio ◽  
Nectar Rewards ◽  
Flower Mites ◽  
Nectar Availability

Abstract:Nectarivorous flower mites can reduce the volume of nectar available to pollinators. The effects of the flower mite Proctolaelaps sp. on nectar availability in flowers of a melittophilous bromeliad Neoregelia johannis (Bromeliaceae) was evaluated in a coastal rain forest in south-eastern Brazil. In a randomized block experiment utilizing 18 flower pairs, one per bromeliad ramet, pollinators (Bombus morio) and mites were excluded, and then nectar volume, sugar concentration and sugar mass were quantified over the anthesis period. Mites significantly reduced nectar volume early in the morning (6h00–8h00), but not later (10h00–12h00). Mites decreased total volume of nectar available up to 22%. Sugar concentration in nectar was higher earlier in the morning, and decreased between 10h00–12h00. The pronounced consumption of nectar by mites during the period of higher sugar concentration reduced the total amount of sugar available to pollinators by 31%. This is the first study showing that flower mites decrease nectar rewards in a melittophilous plant. Because nectar volume by itself incompletely describes nectar production rates and the effects of nectar removal by flower mites on the availability of sugar, our study highlights the inclusion of sugar content in future studies assessing the effects of thieves on nectar production rates.

scholarly journals THE ACCUMULATION OF ELECTROLYTES

1932 ◽  
Vol 15 (6) ◽  
pp. 667-689 ◽  
Author(s):  
W. J. V. Osterhout ◽  
W. M. Stanley
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Aqueous Phase ◽  
Thermodynamic Potential ◽  
Ph Value ◽  
Molecular Form ◽  
External Solution ◽  
Aqueous Layer ◽  
The Difference ◽  
Pass Through

Inasmuch as attempts to explain accumulation by the Donnan principle have failed in the case of Valonia, a hypothesis of the steady state has been formulated to explain what occurs. In order to see whether this hypothesis is in harmony with physico-chemical laws attempts have been made to imitate its chief features by means of a model. The model consists of a non-aqueous layer (representing the protoplasmic surface) placed between an alkaline aqueous phase (representing the external solution) and a more acid aqueous phase (representing the cell sap). The model reproduces most of the features of the hypothesis. Attention may be called to the following points. 1. The semipermeable surface is a continuous non-aqueous phase. 2. Potassium penetrates by combining with an acid HX in the non-aqueous layer to form KX which in turn reacts with an acid HA in the sap to form KA. Since KX is little dissociated in the non-aqueous layer potassium appears to pass through it chiefly in molecular form. 3. The internal composition depends on permeability, e.g., sodium penetrates less rapidly than potassium and in consequence potassium predominates over sodium in the "artificial sap." The order of penetration in the model is the same as in Valonia, i.e., K > Na > Ca > Mg, and Cl > SO4, but the quantitative resemblance is not close, e.g., the difference between potassium and sodium, and chloride and sulfate is much less in the model. 4. The formation of KA and NaA in the sap raises its osmotic pressure and water enters. 5. The concentration of potassium and sodium and the osmotic pressure become much greater inside than outside. For example, potassium may become 200 times as concentrated inside as outside. 6. No equilibrium occurs but a steady state is reached in which water and salt enter at the same rate so that the composition of the sap remains constant as its volume increases. 7. Since no equilibrium occurs there is a difference of thermodynamic potential between inside and outside. At the start the thermodynamic potential of KOH is much greater outside than inside. This difference gradually diminishes and in the steady state has about the same value as in Valonia. The difference in pH value between the internal and external solutions is also similar in both cases (about 2 pH units). 8. Accumulation does not depend on the presence of molecules or ions inside which are unable to pass out. One important feature of the hypothesis is not seen in the model: this is the exchange of HCO3 for Cl-. Experiments on this point are in progress.

scholarly journals Nectar production of pear (Pyrus communis L.) cultivars

2000 ◽  
Vol 6 (3) ◽  
Author(s):  
P. Benedek ◽  
G. Kocsisné Molnár ◽  
J. Nyéki
Keyword(s):  
World Literature ◽  
Fruit Trees ◽  
Significant Negative Correlation ◽  
Sugar Concentration ◽  
Cold Weather ◽  
Nectar Production ◽  
Pyrus Communis L ◽  
The World ◽  
Pear Trees ◽  
Very High

Detailed studies were made on the nectar production of 44, 16 and 18 pear cultivars, respectively, in a cultivar collection of pear during three consecutive years with highly different weather in the blooming. Results clearly show that pear does not necessarily produce small amount of nectar as stated in the world literature. In fact, pear can produce extremely high amount of nectar sometimes much higher than other temperate zone fruit trees species but its nectar production is highly subjected to weather, first of all to air temperature. Low nectar production seems to be more frequent than high one and cold weather can prevent its nectar production at all. On the other hand, results corroborate to the earlier statements on the low sugar concentration of pear nectar. There is a highly significant negative correlation between the amount of nectar produced by pear flowers and its sugar concentration (r = -0.52, n = 291, p< 0.001 for 1996, r = -0.34, n = 197, p< 0.001 for 1998). Sugar concentration in individual flowers may be up, to 40% in exceptional cases but generally it is well below 20%. Very high figures for sugar concentration in pear nectar at the literature seem to be incomprehensible. In contrast of some earlier statement in the literature no real difference could be established in the nectar production of pear cultivars, based on much more measurements than in earlier studies. Very low sugar concentration in pear nectar can explain the fact that the overwhelming majority of honeybees are pollen gatherers at pear trees even in the case of exceptionally high nectar production.  

Penetrability of a marine pseudomonad by inulin, sucrose, and glycerol and its relation to the mechanism of lysis

1970 ◽  
Vol 16 (2) ◽  
pp. 75-81 ◽  
Author(s):  
Francis L. A. Buckmire ◽  
Robert A. MacLeod
Keyword(s):  
Osmotic Pressure ◽  
Exchange Resin ◽  
Sucrose Solution ◽  
Cell Envelope ◽  
Sucrose Concentration ◽  
Ion Exchange Resin ◽  
Cell Preparation ◽  
Cell Envelopes ◽  
Almost All ◽  
Isolated Cell

Cells of a marine pseudomonad were prevented from lysing when suspended in a 0.15 M sucrose solution even after treatment of the sucrose with an ion exchange resin to remove contaminating trace elements. Isolated cell envelopes of the organism in concentrations of sucrose able to prevent lysis of the cells released non-dialyzable hexosamine-containing material into the suspending medium. This did not occur when the envelopes were suspended in concentrations of NaCl able to prevent cell lysis. Glycerol was found to occupy almost all the available fluid space in a packed cell preparation of the organism. Sucrose occupied less space than glycerol, and inulin the least. When the sucrose concentration was increased from 3 mM to 0.2 M, both the sucrose and inulin spaces increased. The results have been interpreted as indicating that sucrose prevents lysis by balancing the internal osmotic pressure of the cells, that the various layers of the cell envelope of the organism differ in their permeability to various solutes, and that the whole cell shrinks in solutions of high osmotic pressure.

scholarly journals The Colloid Osmotic Pressure Across the Glycocalyx: Role of Interstitial Fluid Sub-Compartments in Trans-Vascular Fluid Exchange in Skeletal Muscle

2021 ◽  
Vol 9 ◽  
Author(s):  
Fitzroy E. Curry ◽  
C. Charles Michel
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Osmotic Pressure ◽  
Capillary Pressure ◽  
Interstitial Fluid ◽  
Protein Composition ◽  
Colloid Osmotic Pressure ◽  
Endothelial Glycocalyx ◽  
Fluid Exchange ◽  
Small Pore

The primary purpose of these investigations is to integrate our growing knowledge about the endothelial glycocalyx as a permeability and osmotic barrier into models of trans-vascular fluid exchange in whole organs. We describe changes in the colloid osmotic pressure (COP) difference for plasma proteins across the glycocalyx after an increase or decrease in capillary pressure. The composition of the fluid under the glycocalyx changes in step with capillary pressure whereas the composition of the interstitial fluid takes many hours to adjust to a change in vascular pressure. We use models where the fluid under the glycocalyx mixes with sub-compartments of the interstitial fluid (ISF) whose volumes are defined from the ultrastructure of the inter-endothelial cleft and the histology of the tissue surrounding the capillaries. The initial protein composition in the sub-compartments is that during steady state filtration in the presence of a large pore pathway in parallel with the “small pore” glycocalyx pathway. Changes in the composition depend on the volume of the sub-compartment and the balance of convective and diffusive transport into and out of each sub-compartment. In skeletal muscle the simplest model assumes that the fluid under the glycocalyx mixes directly with a tissue sub-compartment with a volume less than 20% of the total skeletal muscle interstitial fluid volume. The model places limits on trans-vascular flows during transient filtration and reabsorption over periods of 30–60 min. The key assumption in this model is compromised when the resistance to diffusion between the base of the glycocalyx and the tissue sub-compartment accounts for more than 1% of the total resistance to diffusion across the endothelial barrier. It is well established that, in the steady state, there can be no reabsorption in tissue such as skeletal muscle. Our approach extends this idea to demonstrate that transient changes in vascular pressure favoring initial reabsorption from the interstitial fluid of skeletal muscle result in much less fluid exchange than is commonly assumed. Our approach should enable critical evaluations of the empirical models of trans-vascular fluid exchange being used in the clinic that do not account for the hydrostatic and COPs across the glycocalyx.

Effect of plasma osmolality on steady-state fluid shifts in perfused cat skeletal muscle

1993 ◽  
Vol 265 (6) ◽  
pp. R1318-R1323 ◽  
Author(s):  
M. T. Hamilton ◽  
D. S. Ward ◽  
P. D. Watson
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Plasma Volume ◽  
Extracellular Volume ◽  
Plasma Osmolality ◽  
Apparent Volume ◽  
Colloid Osmotic Pressure ◽  
Blue Dye ◽  
Tissue Water ◽  
Wide Range

Fluid redistribution in isolated perfused cat calf muscle caused by rapid increases in plasma osmolality was studied using NaCl or sucrose. Extracellular tracers (51Cr-labeled EDTA or [3H]mannitol) were added to the perfusate 90 min before solutes were added, and samples were taken from plasma immediately before osmolality was increased and 17, 40, and 65 min later. Interstitial fluid volume (IFV) was calculated as extracellular volume (ECV) minus plasma volume (Evans blue dye). Total tissue water changes (delta TTW) were measured by continuous recording of tissue weight. Change in intracellular volume (delta ICV) was obtained from delta TTW--delta IFV. TTW, IFV, ICV, and plasma osmolality were in steady state after 17 min. Changes in hydrostatic and colloid osmotic pressure were insignificant in comparison with small-molecule osmotic pressure changes. The apparent volume of TTW participating in the fluid shift averaged 65 +/- 1 ml/100 g (SE) over a wide range of osmolality increases. In contrast to the large changes in TTW, IFV was not altered by osmolality. Thus decreases in TTW were similar to cell dehydration. Hence, increases in plasma volume induced by hypertonic fluids may come entirely at the expense of cell volume, not interstitial volume.

Osmotic Adaption in the Marine Alga Griffithsia monilis (Rhodophyceae): The Role of Ions and Organic Compounds

1979 ◽  
Vol 6 (4) ◽  
pp. 523 ◽  
Author(s):  
M.A Bisson ◽  
G.O Kirst
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Marine Alga ◽  
Turgor Pressure ◽  
Red Alga ◽  
Steady State Concentration ◽  
Photosynthetic Product ◽  
The Individual ◽  
State Concentration

The red alga G. monilis maintains its turgor pressure constant at 4.05 � 0.14 x 10*5 Pa (179 measurements), or 166 mosmol/kg, over a range of external osmotic pressures from 900 to 1300 mosmol/kg. It is capable of regulating turgor pressure in the dark or when sorbitol is used to increase the external osmotic pressure. Complete regulation of turgor requires 24-36 h, although much of the regulation is accomplished in the first 2 h. The change in II*i is achieved by controlling the concentrations of K+, Na+, and Cl-. In the vacuole, KCl concentration is higher than NaCl, and KCI is usually more important than NaCl in regulating turgor, although the importance of the individual cations varies with specific conditions. The steady-state concentration of the principal photosynthetic product, digeneaside, increases with increasing external osmotic pressure. Its concentration is too low to affect the internal osmotic pressure if it is distributed evenly throughout the cell but, if it is restricted to the cytoplasm, it can play a major role in regulating the volume of the cytoplasm.

A Bioinspired Active Micropump

2015 ◽  
Author(s):  
Prashanta Dutta ◽  
Jin Liu
Keyword(s):  
Fluid Flow ◽  
Osmotic Pressure ◽  
Sucrose Solution ◽  
Chemical Species ◽  
Mass Conservation ◽  
Pressure Head ◽  
Proton Gradient ◽  
Low Flow ◽  
Preliminary Design ◽  
Transporter Proteins

A preliminary design concept is provided for a bioinspired active micropump. The proposed micropump uses light energy to activate the transporter proteins (bacteriorhodopsin protein and sucrose/sugar transporter proteins), which create an osmotic pressure gradient and drive the fluid flow. The purpose of the bacteriorhodopsin protein is to pump proton from the pumping section to the sucrose source for a proton gradient. This proton gradient is used by the sucrose transporter proteins to transport sugar molecules from the sucrose solution chamber to the pumping channel, which generates an osmotic pressure in the pumping section. A numerical model is used to evaluate the performance of the micropump where the concentrations of proton and sucrose molecules are calculated using the conservation of chemical species equations. The fluid flow and pressure field are calculated from momentum and mass conservation equations. Simulation results predict that the micropump is capable of generating a pressure head that is comparable to other non-mechanical pumps. The proposed bioinspired self-sustained micropump will be most effective at low flow rate.

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