Nutrient cycling in grazed pastures. III. Studies on labelling of the grazed pasture system by solid [35S]gypsum and aqueous Mg35S04

1970 ◽  
Vol 21 (3) ◽  
pp. 455 ◽  
Author(s):  
AR Till ◽  
PF May
Keyword(s):  
Steady State ◽  
Nutrient Cycling ◽  
Specific Radioactivity ◽  
Sulphur Content ◽  
Sheep Grazing ◽  
Plant Materials ◽  
Grazed Pastures ◽  
Grazed Pasture ◽  
Sulphur Cycle

35S was applied to eight paddocks either onto strips that comprised 1/30 of the area of the paddock or uniformly over the paddock. It was applied as solid [35S]gypsum or aqueous Mg35SO4 at sulphur levels of either 130 mg/ha or 7.8 kg/ha. The specific radioactivity of wool grown by sheep grazing the paddocks showed that strip and uniform labelling gave similar results, that there was no retention of the applied sulphur in forms that were not eventually available to plants, and that after about 260 days the effective specific radioactivity of the cycling sulphur had approached a steady state. There were significant differences between the specific radioactivities of sulphur in phalaris and clover. The differences in the sulphur application levels produced plant materials having slightly different sulphur contents but the major changes in sulphur content were due to the natural sulphur cycle.

Nutrient cycling in grazed pastures. II. Further observations with [35S] gypsum

1970 ◽  
Vol 21 (2) ◽  
pp. 253 ◽  
Author(s):  
AR Till ◽  
PF May
Keyword(s):  
Nutrient Cycling ◽  
Sheep Grazing ◽  
Grazed Pastures ◽  
Grazed Pasture ◽  
Sulphur Cycle ◽  
Total Soil ◽  
Animal System ◽  
Gypsum Application

The incorporation of sulphur-35 (35S) into the wool of sheep grazing radioactive pasture was measured in two successive experiments on the same site following application of [35S]gypsum. Equilibrium between the applied sulphur and sulphur present prior to the application was established at different rates with different rainfall. After 3 years the sulphur from the original gypsum application was still being turned over in the soil-plant-animal system, there had been no change in the total soil sulphur, and a large portion of soil sulphur did not enter the sulphur cycle. A diagram of a proposed sulphur cycle in grazed pasture is given, and the assumptions made are discussed.

Nutrient cycling in grazed pastures.IV.The fate of sulphur-35 following its application to a small area in a grazed pasture

1971 ◽  
Vol 22 (3) ◽  
pp. 391 ◽  
Author(s):  
AR Till ◽  
PF May
Keyword(s):  
Nutrient Cycling ◽  
Small Area ◽  
Specific Radioactivity ◽  
Positive Evidence ◽  
Grazed Pasture ◽  
Simultaneous Measurements ◽  
Organic Sulphur ◽  
High Specific Radioactivity ◽  
Wide Range ◽  
Extractable Soil

Simultaneous measurements of sulphur content and specific radioactivity were made on soil fractions, two pasture species, and the fleece of grazing animals following the application of high specific radioactivity gypsum labelled with sulphur-35 (35S) to small randomly located sites in grazed pastures. The results show that the extractable soil sulphate was a precursor of plant sulphur and that the organic sulphur fractions in the soil were the source of replenishment of the extractable sulphate pool. Applied sulphur was shown to remain predominantly in the top 7.5 cm of the soil over a period of c. 600 days, and it was from this region that the plants drew their sulphur. The uptake of applied sulphur was initially different between plants of different species. These differences gradually decreased and finally disappeared as the applied sulphur became mixed into all soil sulphur fractions. A wide range of rates of mixing indicated that some fractions of the organic sulphur were recycling very slowly. Positive evidence of recycling of sulphur voided by the animals on the unlabelled areas of the pasture was found, and the rate of translocation of sulphur from the sites of its application to the remainder of the paddock was measured at two rates of stocking.

Impact of soil organic matter on soil properties—a review with emphasis on Australian soils

Soil Research ◽  
2015 ◽  
Vol 53 (6) ◽  
pp. 605 ◽  
Author(s):  
B. W. Murphy
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Nutrient Cycling ◽  
Soil Properties ◽  
Aggregate Stability ◽  
Relevant Information ◽  
Soil Productivity ◽  
Soil Biology ◽  
Productive Capacity ◽  
Plant Materials

A review has been undertaken into how soil organic matter (SOM) affects a range of soil properties that are important for the productive capacity of soils. The potential effect of varying the amount of SOM in soil on a range of individual soil properties was investigated using a literature search of published information largely from Australia, but also including relevant information from overseas. The soil properties considered included aggregate stability, bulk density, water-holding capacity, soil erodibility, soil colour, soil strength, compaction characteristics, friability, nutrient cycling, cation exchange capacity, soil acidity and buffering capacity, capacity to form ligands and complexes, salinity, and the interaction of SOM with soil biology. Increases in SOM have the capacity to have strong influence only the physical properties of the surface soils, perhaps only the top 10 cm, or the top 20 cm at most. This limits the capacity of SOM to influence soil productivity. Even so, the top 20 cm is a critical zone for the soil. It is where seeds are sown, germinate and emerge. It is where a large proportion of plant materials are added to the soil for decomposition and recycling of nutrients and where rainfall either enters the soil or runs off. Therefore, the potential to improve soil condition in the top 0–20 cm is still critical for plant productivity. The SOM through nutrient cycling such as mineralisation of organic nitrogen to nitrate can have an influence on the soil profile.

scholarly journals Regulation of phosphatidate synthesis by secretagogues in parotid acinar cells

1982 ◽  
Vol 204 (2) ◽  
pp. 587-592 ◽  
Author(s):  
S J Weiss ◽  
J S McKinney ◽  
J W Putney
Keyword(s):  
Steady State ◽  
Substance P ◽  
Specific Radioactivity ◽  
Acinar Cells ◽  
Half Time ◽  
Muscarinic Antagonist ◽  
Parotid Acinar Cells ◽  
Rat Parotid ◽  
In Cells

The metabolism of phosphatidate in rat parotid acinar cells was investigated, particularly with regard to the actions of agonists known to act by mobilizing Ca2+. When cells were incubated in medium containing 10 microM-[32P]Pi, phosphatidate was rapidly labelled, approaching an apparent steady-state with a half-time of approx. 20 min. Methacholine provoked a more than doubling of phosphatidate radioactivity, which was reversed by the muscarinic antagonist atropine. These results suggest that phosphatidate labels to near steady-state rapidly and that in cells prelabelled for 60 min the increase in radioactivity induced by agonists probably reflects net synthesis rather than an increase in specific radioactivity. Phosphatidate synthesis in response to methacholine was rapid and occurred, within the resolution of a few seconds, with no measurable latency. Adrenaline and substance P also stimulated phosphatidate synthesis but both agonists were less efficacious than methacholine. A Ca2+ ionophore, ionomycin, did not provoke phosphatidate synthesis. By using a protocol that eliminates the receptor-regulated Ca2+ pool, it was demonstrated that methacholine-induced phosphatidate formation does not come about as a consequence of Ca2+ influx nor of Ca2+ release. These results indicate that the phosphatidate synthesis response has characteristics compatible with its previously suggested role as a primary mediator of membrane Ca2+-gating.

Viability of axillary buds of white clover (Trifolium repens) in grazed pasture

1992 ◽  
Vol 119 (3) ◽  
pp. 345-354 ◽  
Author(s):  
P. C. D. Newton ◽  
M. J. M. Hay ◽  
V. J. Thomas ◽  
H. B. Dick
Keyword(s):  
New Zealand ◽  
White Clover ◽  
Trifolium Repens ◽  
Axillary Buds ◽  
Spring Period ◽  
Grazed Pastures ◽  
Grazed Pasture ◽  
Pattern Of Variation

SUMMARYStolon nodes of white clover were sampled monthly for 18 months from continuously grazed (set stocked) and rotationally grazed pastures in New Zealand. Both pastures were stocked at 22·5 ewes plus lambs/ha. Axillary buds were classified into viability categories using an incubation technique. On average, 54% of nodes had non-viable or dormant buds, 25% had axillary buds that were viable but non-active and 0·1% bore reproductive buds. Although 21% of buds emerged, only 8·5% of nodes bore live branches. Bud activity was strongly inhibited during the spring period of both years and this inhibition could not be removed by incubation.The greatest bud viability occurred at node 4 (from the apex) although 30–40% of the buds at this position were non-viable. This pattern of variation changed somewhat with season. Some viable buds were present at nodes more than 20 from the apex but these were of low vigour. Secondary stolons had different patterns of bud activity from those of primary stolons until they comprised more than 16 nodes.

scholarly journals The redistribution of carbon label by the reactions involved in glycolysis, gluconeogenesis and the tricarboxylic acid cycle in rat liver

1968 ◽  
Vol 110 (2) ◽  
pp. 313-335 ◽  
Author(s):  
D. F. Heath
Keyword(s):  
Carbon Dioxide ◽  
Steady State ◽  
Rat Liver ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
State Theory ◽  
Variable Rate ◽  
Acid Cycle ◽  
Constant Rate

A scheme is presented that shows how the reactions involved in gluconeogenesis, glycolysis and the tricarboxylic acid cycle are linked in rat liver. Equations are developed that show how label is redistributed in aspartate, glutamate and phosphopyruvate when it is introduced as specifically labelled pyruvate or glucose either at a constant rate (steady-state theory) or at a variable rate (non-steady-state theory). For steady-state theory the fractions of label introduced as specifically labelled pyruvate that are incorporated into glucose and carbon dioxide are also given, and for both theories the specific radioactivities of aspartate and glutamate relative to the specific radioactivity of the substrate. The theories allow for entry of label into the tricarboxylic acid cycle via both oxaloacetate and acetyl-CoA, for 14CO2 fixation and for loss of label from the tricarboxylic acid cycle in glutamate, but not for losses in citrate. They also allow for incomplete symmetrization of label in oxaloacetate due to incomplete equilibration with fumarate both in the extramitochondrial part of the cell and in the mitochondrion on entry of oxaloacetate into the tricarboxylic acid cycle. In the latter case failure both of oxaloacetate to equilibrate with malate and of malate to equilibrate with fumarate are considered.

scholarly journals Synthesis and turnover of plasma-membrane proteins and glycoproteins in a neuroblastoma cell line

1976 ◽  
Vol 154 (1) ◽  
pp. 57-64 ◽  
Author(s):  
R A Mathews ◽  
T C Johnson ◽  
J E Hudson
Keyword(s):  
Steady State ◽  
Membrane Proteins ◽  
Polyacrylamide Gel Electrophoresis ◽  
Surface Membrane ◽  
Neuroblastoma Cell ◽  
Sodium Dodecyl ◽  
Neuroblastoma Cells ◽  
Specific Radioactivity ◽  
Neuroblastoma Cell Line ◽  
Total Membrane

A kinetic analysis of the appearance of 14C-labelled proteins in the surface membranes isolated from exponentially growing neuroblastoma cells (N2a) showed that the total membrane proteins reached a steady-state specific radioactivity in 18-20 h. However, examination of individual protein bands resolved by sodium dodecyl sulphate-urea-polyacrylamide-gel electrophoresis illustrated that differences in the kinetics of specific surface-membrane proteins could be detected. Although most of the protein bands reached a steady-state specific radioactivity at a time similar to that for total membrane proteins, at least two bands (mol. wt. 180000 and 130000) attained the steady-state within 8-10 h. It was shown by the use of dual-labelling techniques that these two protein bands turned over in the surface membranes of neuroblastoma N2a cells at least 180 and 150% faster than the total membrane protein. These two proteins were glycosylated and located on the outer surface of the cells, since they were labelled with radioactive carbohydrates and readily removed by treatment of the intact neuroblastoma cell with proteinases.

Study of Micro-Inclusion of 20g Steel

2013 ◽  
Vol 634-638 ◽  
pp. 1864-1868
Author(s):  
Shuo Ming Wang ◽  
Cheng Liang Du ◽  
Ju Gao
Keyword(s):  
Particle Size ◽  
Steady State ◽  
System Analysis ◽  
Sulphur Content ◽  
Complex Inclusion ◽  
Secondary Oxidation ◽  
Volume Rate ◽  
Compound Casting ◽  
Al2o3 Inclusion

According to the production process of 20g steel(120t BOF→ LF→ CC), some system analysis are introduced to research on the content of T[O] and [N] and the type, source, composition and quantity of micro inclusions in refining process, pouring process and casting billet. The results of the study show: the content of T[O] is 93.2ppm in the normal billet which is 37.8ppm more than that at steady state in the export of tundish. The content of T[O] is 140.5ppm in the compound casting billet which is 70.133ppm more than that at non-steady state in the export of tundish. The secondary oxidation of mould is serious at casting progress. In billet, the quality of CaS-SiO2-Al2O3 complex inclusion is the most, the quality of MnS inclusion is the second, and the quality of Al2O3 inclusion is the least. The sulphur content in micro-inclusion of billet is higher. The sulphur content in CaS-SiO2-Al2O3 complex inclusion is 3~15%, the sulphur content in MnS inclusion is 25%. The particle size of less than 10μm in micro-inclusions is the largest. The particle size of 0~5μm is about 60%, the particle size of 5~10μm is about 35%, the particle size of 10~15μm is about 5%. The average total volume rate of micro-inclusion is 0.149% in normal billet. The average total volume rate of micro-inclusion is 0.184% in compound casting billet which is 1.23 times than normal billet. The number of micro-inclusion is 36.5/ mm2 in normal billet. The number of micro-inclusion is 58.5/ mm2 in compound casting billet which is 60.27% higher than normal billet. The non-steady state casting has serious influence on billet cleanliness.

Producing milk with uniform high selenium concentrations on commercial dairy farms

2011 ◽  
Vol 51 (2) ◽  
pp. 87 ◽  
Author(s):  
P. T. Doyle ◽  
C. R. Stockdale ◽  
M. L. Jenkin ◽  
G. P. Walker ◽  
F. R. Dunshea ◽  
...  
Keyword(s):  
Steady State ◽  
Milk Powder ◽  
Dairy Farms ◽  
Pilot Scale ◽  
Scale Production ◽  
Milk Protein Concentrate ◽  
Grazed Pasture ◽  
High Selenium ◽  
Predicted Values ◽  
Protein Milk

Six herds on five commercial dairy farms were involved in the production of high selenium (Se) milk. The farms had a range of herd sizes, herd structures, feeding systems and milk production per cow. On all farms, pelleted concentrate supplements containing Se yeast were fed twice daily in the dairy for 16 days. The objectives were to: (1) produce milk with Se concentrations exceeding 225 μg/kg on the five farms for pilot-scale production of a high protein milk powder; (2) validate a predictive relationship between Se intake and milk Se concentration developed in research; and (3) examine the time taken from the introduction of Se yeast to steady-state concentrations of Se in milk under a range of commercial farming conditions. We hypothesised that the relationship between Se intake and its concentration in milk found in research would apply on commercial farms. Daily Se intake, which was primarily from Se yeast in the pelleted concentrates, varied from 35 to 51 mg Se/cow. Grazed pasture and conserved forage contributed less than 1 mg Se/cow on all farms. The time taken from the introduction of pellets containing Se yeast to steady-state milk Se concentrations was 4–7 days. The steady-state Se concentrations in milk varied from 166 to 247 µg/kg, but these concentrations were only 55–72% of predicted values. All the milk produced from the five farms on the last 2 days of feeding of Se-enriched pellets was used to produce a milk protein concentrate with a Se concentration of 5.4 mg/kg. Factors that might have affected Se incorporation into milk and the implications of these results for commercial production of high Se milk or milk products are discussed.

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