scholarly journals Pathway and driving forces of selenite absorption in wheat leaf blades

2019 ◽  
Vol 65 (No. 12) ◽  
pp. 609-614
Author(s):  
Lianhe Zhang ◽  
Jinyong Yang ◽  
Zihao Fu ◽  
Yihan Fu ◽  
Sinan Liu ◽  
...  
Keyword(s):  
Inorganic Phosphate ◽  
Absorption Rate ◽  
Driving Forces ◽  
Wheat Crop ◽  
Concentration Gradients ◽  
Human Diet ◽  
Mesophyll Cells ◽  
Respiratory Inhibitors ◽  
Wheat Leaf ◽  
Se Deficiency

Selenium (Se) deficiency in the human diet is a widespread problem. Se biofortification of wheat crop by spraying foliage with selenite could effectively increase Se intake by enhancing the Se concentration in wheat grains. However, pathway and driving forces of selenite absorption in wheat leaf blades are not fully understood. In this study, the effects of selenite-applied concentration, selenite-exposed duration, stomatal inhibitors, respiratory inhibitors, and competitive anions on selenite absorption in wheat leaf blades were investigated. The results indicated that the selenite absorption rate increased linearly with increasing selenite concentrations, but it decreased greatly and reached a low level with treatment times of 4 h and longer. Stomatal inhibitors significantly inhibited selenite absorption. Respiratory inhibitors and inorganic phosphate (P<sub>i</sub>) strongly inhibited selenite absorption. Therefore, selenite passively enters wheat leaf blades via cuticle and stomata, and then enters mesophyll cells via P<sub>i</sub> transporters. Concentration gradients and selenite uptake by mesophyll cells provide continual driving forces for selenite absorption in leaf blades.

scholarly journals Key factors affect selenite absorption in wheat leaf blades: pH, temperature, light intensity and leaf position

2020 ◽  
Vol 66 (No. 9) ◽  
pp. 431-436
Author(s):  
Lianhe Zhang ◽  
Liu Sinan ◽  
Yu Feiyan ◽  
Fu Zihao ◽  
Yang Jinyong ◽  
...  
Keyword(s):  
Light Intensity ◽  
Absorption Rate ◽  
Low Ph ◽  
Leaf Position ◽  
Key Factors ◽  
Mesophyll Cells ◽  
Effective Measure ◽  
Ph Values ◽  
Wheat Leaf ◽  
Effects Of Ph

Foliage-spraying selenite solution is an effective measure to enhance selenium (Se) concentration in wheat grains. However, how pH, temperature, light intensity, and leaf position affects selenite absorption in wheat leaf blades is not fully understood. In this study, the effects of pH, temperature, light intensity, and leaf position on selenite absorption in wheat leaf blades were investigated. The results indicated that the selenite absorption rate dramatically decreased with increasing pH. Further study revealed that aquaporin inhibitors such as HgCl<sub>2</sub> and AgNO<sub>3</sub> strongly inhibited selenite absorption at pH 3.0. Light and higher temperatures significantly promoted selenite absorption. Newly expanded leaf blades had higher rates of selenite absorption than younger and older leaf blades. Thus, higher rates of selenite absorption in leaf blades should attribute to the entrance of selenite into mesophyll cells via aquaporins in the form of H<sub>2</sub>SeO<sub>3</sub> at low pH values. Foliage-spraying selenite solution on upper leaf blades at lower pH values benefited to increase the selenite absorption rate in wheat leaf blades.  

scholarly journals Role of facilitative glucose uptake in the glucose-inorganic phosphate-mediated retardation and inhibition of development in different strains of mouse embryos

Reproduction ◽  
2002 ◽  
pp. 691-700 ◽  
Author(s):  
L Scott ◽  
DG Whittingham
Keyword(s):  
Glucose Uptake ◽  
Glucose Transport ◽  
Inorganic Phosphate ◽  
Mouse Embryos ◽  
Concentration Gradients ◽  
Morula Stage ◽  
Different Strains ◽  
Hybrid Development

Mouse embryos from different strains develop differently in vitro depending on the composition of the culture medium, and in particular on the presence or absence of glucose and inorganic phosphate. Glucose is both stimulatory and inhibitory in certain conditions. Glucose uptake by cells can be passive, down concentration gradients, or active, through sodium driven pumps, or can occur through facilitative transport. This study investigated the effects of inhibition of facilitative glucose transport on the glucose-inorganic phosphate-mediated blocks in development in three different strains of mouse embryo, CF-1, CD-1 and an F2 hybrid. Development of CF-1 and CD-1 embryos is blocked in medium containing glucose and inorganic phosphate but not in medium containing glucose alone, and F2 embryos are not affected. Inhibition of facilitated glucose transport to the eight-cell-morula stage in CF-1 and CD-1 embryos resulted in development in medium containing both glucose and inorganic phosphate, indicating that the prevention of facilitative glucose uptake can overcome the developmental block. Removal of inhibition before the eight-cell-morula stage resulted in total arrest of CF-1 embryos and minimum development of CD-1 embryos. F2 embryos are not affected by inorganic phosphate and glucose and showed no response to the transporter inhibitor at any stage. These data support the contention that facilitated glucose transport is active in embryos, is phosphate-dependent and that its inhibition can overcome the glucose-inorganic phosphate-mediated developmental blocks in mouse embryos.

scholarly journals Electron Probe Microanalysis of Potassium and Chloride in Freeze-Substituted Leaf Sections of Zea Mays

1973 ◽  
Vol 26 (5) ◽  
pp. 1015 ◽  
Author(s):  
CK Pallaghy
Keyword(s):  
Potassium Concentration ◽  
Cell Types ◽  
Bundle Sheath ◽  
Concentration Gradients ◽  
Mesophyll Cells ◽  
Transmission Electron ◽  
Bundle Sheath Cells ◽  
Scanning Transmission ◽  
Diamond Knife ◽  
Sheath Cells

Small sections of leaves were floated on distilled water under either light or dark conditions, and were freeze-substituted in a 1 % solution of osmium tetroxide in acetone at -78�C followed by embedding in an epoxy resin. Approximately I-11m-thick sections were cut using a dry diamond knife and examined by scanning transmission electron microscopy. The relative concentrations of potassium and chloride in subcellular compartments were determined using an energy dispersive X-ray analyser. The concentration of sodium in the leaf (1�7 m-equivjkg of wet tissue) was too low to be detected by this method. The spatial resolution of this technique was sufficient to distinguish between concentrations in the chloroplasts, cytoplasm, vacuole, and nuclei. The concentration of chloride in stomata and some other epidermal cells was very much higher than in either mesophyll or bundle sheath cells. The potassium concentration in some vascular cells was at least two- to threefold higher than that in mesophyll or bundle sheath cells. The Cl : K ratio in mesophyll and bundle sheath cells resembled that in the solution (0 �10) used for growing the plants. The concentration of chloride in the "free" cytoplasm of mesophyll cells was always very low. Significant differences were found in the "ion" relations of mesophyll and bundle sheath cells. Whereas the ratio of potassium concentration between the vacuole and chloroplasts of mesophyll cells was high (1 �19) in the light and low (0�65) in the dark, the opposite was true for bundle sheath cells-O� 65 and 0�86 respectively. The ratio of potassium concentration between the vacuo les of mesophyll and those of bundle sheath cells was 1 �48 in the light, but only 0�76 in the dark. These concentration gradients are discussed in relation to a possible transfer of organic acid salts of potassium between these two cell types.

The use of a Thiry-Vella loop of jejunum to study the intestinal absorption of calcium and inorganic phosphate in the conscious pig

1978 ◽  
Vol 39 (3) ◽  
pp. 431-439 ◽  
Author(s):  
J. Fox ◽  
A. D. Care ◽  
R. Swaminathan
Keyword(s):  
Inorganic Phosphate ◽  
Absorption Rate ◽  
Water Movement ◽  
Jejunal Loop ◽  
Jejunal Mucosa ◽  
Two Component System ◽  
Rapid Absorption ◽  
Perfusion Solution ◽  
Two Component ◽  
Daily Changes

1. Pigs, each surgically prepared with a Thiry-Vella jejunal loop were used to study the absorption of calcium and inorganic phosphate from the intestine.2. The loops were perfused daily for 6–8 h with a nutrient solution and absorption from the perfusate was measured.3. The technique employed minimized atrophy of the jejunal mucosa and enabled the measurement of hourly or daily changes in absorption rate of components of the luminal fluid.4. No differences were observed when polyethylene glycol (PEG; molecular weight 4000), [14C]PEG or 51Cr-EDTA were used as markers of net water movement.5. Increasing the concentration of Ca in the perfusate resulted in the demonstration of a two-component relationship between net absorption rate of Ca and intraluminal Ca concentration. An initial rapid absorption rate from 0 to 4 mm was found, then a slower rate from approximately 5 mm upwards which did not saturate at the highest concentration tested (25 mm).6. Increasing the concentration of phosphate in the perfusion solution increased the net absorption of phosphate from that solution. Although a two-component system, similar to that for Ca, was not evident, net absorption of phosphate was not saturated at the highest concentration tested (50 mm).7. The absorption of Ca was unaffected by the presence of phosphate in the solution but Ca (2.5 mm) enhanced the absorption of phosphate.

scholarly journals The effect of ruminal phosphate concentration on the absorption of calcium, phosphorus and magnesium from the reticulo-rumen of the sheep

1989 ◽  
Vol 61 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L. J. Beardsworth ◽  
P. M. Beardsworth ◽  
A. D. Care
Keyword(s):  
Inorganic Phosphate ◽  
Absorption Rate ◽  
Rumen Fluid ◽  
Phosphate Concentration ◽  
Potential Difference ◽  
Mineral Analysis ◽  
Basic Composition ◽  
Initial Concentration ◽  
Calcium Phosphorus ◽  
Conscious Sheep

1. The absorption rates of calcium, inorganic phosphate (P1) and magnesium were determined from buffered solutions placed in the temporarily isolated and washed reticulo-rumen of conscious sheep. The basic composition of these solutions was similar to that found in supernatant fractions of ultracentrifuged rumen contents.2. The Pi concentrations studied in these solutions were 2, 8·7, 14, 17·3 and 38 mmol/l. The initial concentration of Ca was 2·0 mmol/l and that of Mg was 2.5 mmol/l in all experiments.3. Increasing the Pi concentration in the rumen solution from 2 to 38 mmol/l resulted in increases in the net absorption rates of both Ca and Pi, and a decrease in the potential difference across the wall of the rumen.4. Similarly, increasing the Pi concentration from 2 to 17·3 mmol/l resulted in an increase in the net absorption rate of Mg from the rumen.5. Mineral analysis of strained rumen fluid or a 30000 g centrifugate of strained rumen fluid revealed a reduced Pi concentration in sheep fed on frozen spring grass as opposed to the pellet + hay diet. The values obtained were within the range studied.

scholarly journals Energy coupling to the transport of inorganic phosphate in Escherichia coli K12

1979 ◽  
Vol 178 (1) ◽  
pp. 133-137 ◽  
Author(s):  
H Rosenberg ◽  
R G Gerdes ◽  
F M Harold
Keyword(s):  
Escherichia Coli ◽  
Energy Source ◽  
Inorganic Phosphate ◽  
Energy Coupling ◽  
Phosphate Transport ◽  
Proton Motive Force ◽  
High Concentration ◽  
Concentration Gradients ◽  
Transport Of Inorganic Phosphate ◽  
Pst System

The nature of the energy source for phosphate transport was studied in strains of Escherichia coli in which either one of the two major systems (PIT, PST) for phosphate transport was present. In the PIT system, phosphate transport is coupled to the proton-motive force. The energy source for the PST system appears to be phosphate-bond energy, as has been found in other systems involving binding proteins. High concentration gradients of phosphate (between 100 and 500) are established by both systems.

Thermodynamics of irreversible processes

2005 ◽  
Author(s):  
Boris S. Bokstein ◽  
Mikhail I. Mendelev ◽  
David J. Srolovitz
Keyword(s):  
Driving Forces ◽  
Open Systems ◽  
Electrical Current ◽  
Heat Fluxes ◽  
Irreversible Processes ◽  
Concentration Gradients ◽  
Thermodynamics Of Irreversible Processes ◽  
Energy Current ◽  
Thermodynamic Forces ◽  
Classical Thermodynamics

The thermodynamics of irreversible processes, formulated by Onsager and Prigogine, considers small deviations from equilibrium in open systems. Despite the fact that the name contains ‘‘thermodynamics,’’ this is a type of kinetic theory that describes the rates of irreversible processes. Since there are no currents of any type in thermodynamic equilibrium, the concept of a current is never used in classical thermodynamics. On the other hand, the thermodynamics of irreversible processes introduces currents as the rates at which processes proceed: the heat or energy current (measured in J/s), matter current (measured in mole/s or kg/s), charge or electrical current (measured in C/s or Amps). Since these currents have a direction and magnitude, they are vectors. The thermodynamics of irreversible processes also considers scalar currents (e.g. rates of chemical reactions) and tensor currents (e.g. momentum currents). In this text, we will focus on current densities or fluxes (that is the current per unit area) rather than currents themselves. The dimensions of the currents described above can be converted to the dimensions of fluxes by dividing through by area or m2. Associated with each flux is a driving force. These forces are known as thermodynamic forces. How can we determine these driving forces? What is the relation between fluxes and driving forces? The answers to these questions can be found in the thermodynamics of irreversible processes briefly described in this chapter. Onsager’s first postulate states that the flux of property i ( ji) is a linear function of all thermodynamic forces, Xk, acting in the system where Lik are called Onsager (or kinetic) coefficients. This postulate was formulated as a generalization of a wide body of experimental observations. In fact, long before Onsager’s work it was known that the heat fluxes are proportional to temperature gradients (Fourier’s law, 1824), charge fluxes are proportional to electric potential gradients (Ohm’s law, 1826), and matter fluxes are proportional to concentration gradients (Fick’s law, 1855). However, Onsager’s contribution was the inclusion of the word ‘‘all’’ in his first postulate.

The physiology of host–parasite relations. XIX. Further observations on nucleoprotein changes in wheat leaf nuclei during rust infection

1968 ◽  
Vol 46 (1) ◽  
pp. 11-16 ◽  
Author(s):  
P. K. Bhattacharya ◽  
Michael Shaw ◽  
J. M. Naylor
Keyword(s):  
Stem Rust ◽  
Rust Fungus ◽  
Puccinia Graminis ◽  
Mesophyll Cells ◽  
Rust Infection ◽  
Puccinia Graminis Tritici ◽  
Wheat Leaf ◽  
Host Parasite

Cytophotometric measurements of DNA (Feulgen) and protein-bound lysine and arginine (fluorodinitrobenzene-Sakaguchi) were made on nuclei in mesophyll cells of infected and uninfected leaves of Little Club wheat at intervals of 2 to 4 days up to 13 days after inoculation with uredospores of race 15B of the stem rust fungus (Puccinia graminis tritici Erikss. and Henn.). No change in host DNA was found within 6 days after inoculation, but there were marked decreases in protein-bound lysine and arginine as early as 2 days after inoculation. The DNA/lysine and DNA/arginine ratios were higher in rust-affected host nuclei, but infection did not alter the ratio of protein-bound lysine to arginine. In another series of measurements it was shown that rust infection caused striking increases in the volume and the RNA and protein contents of host nucleoli. These changes persisted even in advanced infections.All the results are consistent with our earlier observations and indicate that profound changes in nuclear metabolism are induced by infection with the rust fungus.

scholarly journals Improving the efficacy of selenium fertilizers for wheat biofortification

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Chandnee Ramkissoon ◽  
Fien Degryse ◽  
Rodrigo C. da Silva ◽  
Roslyn Baird ◽  
Scott D. Young ◽  
...  
Keyword(s):  
Human Diet ◽  
Wheat Grains ◽  
Soil Application ◽  
N Fertilizers ◽  
Se Deficiency ◽  
Pot Trial ◽  
Staple Crops ◽  
Set Up ◽  
Nitrogen Phosphorus

AbstractIncreasing the selenium (Se) concentration of staple crops by fertilization is a valuable pathway to increase Se in the human diet, thus preventing Se deficiency. A pot trial was set up to investigate whether the application of 3.33 µg kg−1 of Se (equivalent to 10 g ha−1) to wheat can be made more efficient by its co-application with macronutrient carriers, either to the soil or to the leaves. In the soil, Se was applied either on its own (selenate only) or as a granular, Se-enriched macronutrient fertilizer supplying nitrogen, phosphorus, potassium or sulfur. Selenium was also applied to leaves at head emergence with, or without, 2% w/v N fertilizers. With grain Se concentrations varying from 0.13–0.84 mg kg−1, soil application of selenate-only was 2–15 times more effective than granular Se-enriched macronutrient fertilizers in raising grain Se concentrations. Co-application of foliar Se with an N carrier doubled the Se concentration in wheat grains compared to the application of foliar Se on its own, the majority of which was in the highly bioavailable selenomethionine fraction. Results from this study demonstrate the possibility of improving the efficacy of Se fertilizers, which could enrich crops with Se without additional application costs in the field.

Water Pathways in Wheat Leaves. II. Water-Conducting Capacities and Vessel Diameters of Different Vein Types, and the Behaviour of the Integrated Vein Network

1985 ◽  
Vol 12 (2) ◽  
pp. 183 ◽  
Author(s):  
DP Altus ◽  
MJ Canny ◽  
DR Blackmann
Keyword(s):  
Theoretical Analysis ◽  
Leaf Blade ◽  
Integrated System ◽  
Equivalent Diameter ◽  
Mesophyll Cells ◽  
Wheat Leaf ◽  
Wheat Leaves ◽  
Physical Spaces ◽  
Cross Connect ◽  
Large Vessels

The water-conducting capacity of the lateral veins of the wheat leaf, measured by the velocity of movement of a dye marker, decreases with distance along the leaf towards the tip. The laterals contain a number of small (up to 10 �m) diameter vessels as well as two or three relatively large (up to 45 �m) diameter vessels. The largest vessel in each decreases in diameter with distance along the leaf towards the tip, resulting in the decreased velocity of conduction. The large vessels represent physical spaces through which laminar flow can occur; however, the flow rate is slower than that predicted by the Hagen-Poiseuille law for pipes of equivalent diameter. The intermediate veins contain only several 7-10 �m diameter vessels, and the diameter of the largest vessel in these veins does not change along the length of the leaf. The number of 7-10 �m diameter vessels per vein also remains unchanged. The water- conducting capacity of an intermediate vein is therefore constant along the length of the leaf. The transverse veins that cross-connect neighbouring longitudinal veins all have similar water-conducting capacity regardless of location in the leaf. These measurements support the view that the lateral veins serve to supply water from the base of the leaf to the tip, while the intermediate and transverse veins form a distribution network carrying the water across the leaf to the mesophyll cells. A theoretical analysis is made of the behaviour of the network as an integrated system. Assumed transpiration rates are imposed on the model to find what the pressure gradient along the leaf blade is, what pressures would be produced at the nodes of the network, and what fluxes would result through the vein elements of it. The model predicts movements of water in the intermediate veins very similar to those observed in a previous paper and suggests that the network responds to changes in supply or demand by producing minima of similar pressure in the distributing veins at different distances from the supplying longitudinal veins.

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