Showing papers on "Phosphorus published in 1975"

Comparison of the effects of a localised supply of phosphate, nitrate, ammonium and potassium on the growth of the seminal root system, and the shoot, in barley

Abstract: SUMMARY Barley plants were grown for 21 days in sand culture, continuously irrigated with nutrient solution. The rooting depth was divided into three compartments, one above another, such that different zones of the root system could be supplied with very low or high concentrations of a single inorganic nutrient, all other nutrients being maintained at a high concentration. Exposure of parts of the main seminal roots (axes) to high concentrations of phosphate caused a localized promotion of the initiation and subsequent extension of both first and second order laterals, compared with zones receiving very low concentrations of phosphate. This resulted in considerable modification to root form, but with only a small depression in shoot growth, compared with control plants receiving an ample supply to all parts of the root system. The extension of seminal axes was little affected by the concentration of phosphate to which they were exposed. Similar responses to those described for phosphate occurred with variation in concentration of nitrate or ammonium, but with potassium a localized supply promoted the growth of laterals to approximately the same extent as controls throughout the entire root system. The experiments show that adequate external concentrations of nitrogen and phosphorus are required by any part of the root system for optimal growth of laterals, but not axes. Possible mechanisms which compensate shoot growth when nutrients are supplied to only part of the root system, and agronomic implications, are discussed.

Input-output models

Abstract: Elementary mass balance and export models are explored in relation to eutrophication as caused by phosphorus and nitrogen. New criteria for phosphorus loading are given in relation to the ratio ‘mean depth-water fill-in-time’ $$(\bar z/\tau _w )$$ . The results suggest that lakes having long water renewal times are much more sensitive to phosphorus loading than would appear from mean depth only. Further, from comparison of the relative residence time of nitrogen and phosphorus, it is deduced that—with increasing eutrophication—the nitrogen metabolism is speeded up beyond the point of simple proportionality which would explain the transition from phosphorus to nitrogen limitation in highly eutrophied lakes. It is further suggested that the principles derived from eutrophication in regard to the metabolism of phosphorus and nitrogen in lakes are applicable also to other environmental compartments and stress factors.

Lipids of yeasts.

Abstract: INTRODUCTION ............................................................. 198 CELLULAR LIPIDS ......................................................... 198 Extraction .................................................................. 198 Subcellular Distribution .................................................... 198 Cytoplasmic (plasma) membrane .......................................... 198 Intracytoplasmic elements ................................................. 199 Cell wall ................................................................. 199 LIPID COMPONENTS ....................................................... 199 Fatty Acids ................................................................. 199 Chemical nature .......................................................... 199 Mutant strains ............................................................ 201 Biosynthesis ............................................................. 201 Biological significance .................................................... 202 Taxonomy ................................................................ 202 Hydrocarbons and Sterols ................................................... 202 Hydrocarbons ............................................................ 202 Sterols (i) Chemical nature ................................................ 202 (ii) Mutant strains......................................................... 204 (iii) Biosynthesis ......................................................... 204 (iv) Biological significance ................................................ 206 Glycerophospholipids ....................................................... 207 Chemical nature .......................................................... 207 Biosynthesis ............................................................. 208 Cellular distribution ...................................................... 208 Biological significance .................................................... 208 Sphingolipids ............................................................... 209 Chemical nature .......................................................... 209 Biological significance .................................................... 209 Glycolipids ................................................................. 209 FACTORS INFLUENCING CELLULAR LIPID COMPOSITION ..... ......... 209 Growth Cycle ............................................................... 209 Sporulation ................................................................. 210 Carbon Source ............................................................. 210 Glucose .................................................................. 210 Hydrocarbons ............................................................ 211 Nutrients ................................................................... 213 Nitrogen ................................................................. 213 Phosphorus .............................................................. 213 Growth factors ........................................................... 213 (i) Inositol ................................................................ 213 (ii) Pantothenic acid ...................................................... 213 (iii) Vitamin B6 ........................................................... 213 (iv) Biotin ................................................................ 214 Miscellaneous Additives .................................................... 214 Sodium chloride .......................................................... 214 Choline and ethanolamine ................................................ 214 Benzo(a)pyrene and dibenzanthracene ..................................... 214 Propanediol .............................................................. 214 Oxygen ..................................................................... 214 Respiratory-deficient (Crabtree-positive) yeasts (i) Lipid composition ....... 214 (ii) Lipid supplementation of growth medium ....... ....................... 215 Respiratory-sufficient (Crabtree-negative) yeasts ...... .................... 216 Temperature ............................................................... 216 pH ..................................................................... 217 CONCLUDING COMMENTS ................................................. 217 LITERATURE CITED ....................................................... 219

The phosphorus budget of Cameron Lake, Ontario: The importance of flushing rate to the degree of eutrophy of lakes1

Abstract: The total phosphorus budget of Cameron Lake is described for two 12-month periods. Although the phosphorus loadings were high (1.70 and 2.21 g m−2 yr−1), the lake is not cutrophic because a high flushing rate counteracts the high loading. A plot of L(1–R)/ρ, where L is phosphorus loading, R is the retention coefficient of phosphorus in the lake, and ρ is the hydraulic flushing rate, vs. (z), the mean depth, is suggested as a means of relating lake trophic state to phosphorus loading. This formulation accurately predicted that nearby Four Mile Lake would be almost identical to Cameron Lake in terms of degree of cutrophy despite the fact that Four Mile Lake’s phosphorus load is 20 times less than that of Cameron Lake.

An empirical method of estimating the retention of phosphorus in lakes

Abstract: The relationship between phosphorus retention and several other lake and watershed parameters was examined for 15 lakes. A model relating the areal water load (qs) to phosphorus retention was proposed:Rp = 0.426 exp (−0.271qs) + 0.574 exp (−0.00949qs). This model was found to be theoretically sound, and the predicted and measured values were in close agreement (r = 0.94).

Nitrate, phosphorus, and sulfate in subsurface drainage water

Abstract: Measurements made over a 4-year study of flow and NO₃-N, PO₄-P, total P, and SO₄-S content of subsurface drainage water from tile-drained cropland indicate that annual nutrient losses are highly variable. Annual losses of phosphorus, SO₄-S, and NO₃-N ranged from 0 to 0.04, 0 to 32, and 0 to 93 kg/ha, respectively, being very dependent on the amount of water lost. Because of low concentrations of phosphorus, losses with subsurface drainage water were insignificant when compared with losses associated with surface runoff. Concentrations of SO₄-S and NO₃-N were seemingly inversely related. Tile drainage water with consistently high NO₃-N content relative to surface runoff (> 10 ppm even under the low-fertility management of this study, 224 kg/ha of N over 5 years) is believed responsible for the high NO₃-N content sometimes found in a river draining central Iowa. The nitrate content of water from the saturated and unsaturated zones of the soil profile indicates that waves or pulses of water, with different NO₃-N concentrations, moving through the soil profile cause the observed variation of NO₃-N content of subsurface drainage water with time and flow rate. Such variations illustrate the difficulty of identifying water-quality trends from limited data.

Eutrophication of Dutch coastal waters.

Abstract: The concentrations of phosphorus and nitrogen compounds in the river Rhine have increased by a factor of about 7 since 1932; in recent years the rate of increase for P has been higher than for N. The concentration of reactive silicate, which is low in summer, has remained essentially constant. Because in the Southern Bight of the North Sea the contribution of nutrients from the deep oceanic reservoir is minor, these increases in riverborne nutrients have had a marked influence on nutrient values and nutrient ratios of the whole area, but especially so on the narrow strip of water along the Dutch Coast, which has an average salinity of 30%ₒ. These changes have caused silicon to be the first depleted nutrient element, limiting diatom blooms. It is shown that the spring bloom of Phaeocystis poucheti is occasionally able to consume all phosphorus, leaving some nitrogen. However, on the average the phosphorus and nitrogen left over by diatoms after all reactive silicate has been depleted is not consumed by other phytoplankton species. In the strip of 30%ₒ salinity water along the coast daily primary production may be up to 3500 mg carbon/m 2 , but yearly primary production is not very high. The vegetative season lasts only about 6 months, due to the influence of turbidity, and is characterized by a succession of periods with high and low productivity. This instability in the phytoplankton regime sometimes causes very high phytoplankton crops and at other times advection and diffusion of unused nutrient loads from the rivers to other parts of the North Sea.

Physiological Responses of Semiarid Grasses. I The Influence of Phosphorus Supply on Growth and Phosphorus Absorption

Abstract: Experiments were carried out under controlled conditions to investigate the physiological bases for species differences in yield and nutrient responses to variations in phosphorus supply. Buffel grass (Cenchrus ciliaris), and to a less extent Mitchell grass (Astrebla elymoides), showed a much larger yield response to increasing phosphorus supply than mulga grass (Thyridolepis mitchelliana). Mitchell and mulga grasses had much lower relative growth rates than buffel grass. Mulga grass required a lower external phosphorus concentration for optimal growth than Mitchell and buffel grasses; this was attributed to its superior system for absorbing and transporting phosphate from low concentrations, but was not associated with any yield advantage, yield being related more to the photosynthetic than to the nutritional characteristics of the plants. Differences between species in their external phosphorus requirements for growth and their distribution in semiarid Queensland are discussed.

Whole-lake eutrophication experiments with phosphorus, nitrogen and carbon

Abstract: (1975). Whole-lake eutrophication experiments with phosphorus, nitrogen and carbon. SIL Proceedings, 1922-2010: Vol. 19, No. 4, pp. 3221-3231.

Enrichment experiments for determining nutrient limitation: Four methods compared1

Abstract: Four nutrient bioassay techniques were compared in studies of an oligotrophic, soft-water lake in New Hampshire. Enrichments of large polyethylene enclosures, continuous cultures of the natural phytoplankton community, and long term 14C bioassays agree in demonstrating that nitrogen and phosphorus limit phytoplankton growth in this lake. However, in short term (4–30 h) 14C bioassays, nitrogen and phosphorus enrichments did not stimulate phytoplankton production. Care should be exercised in extrapolating results from short term, bottle bioassays to measures for controlling eutrophication.

Requirement of Atlantic Salmon for Dietary Phosphorus

Abstract: Triplicate lots of young Atlantic salnon (Salmo salar) were fed a diet containing graded levels of supplemental inorganic phosphorus. The basal diet, containing mainly dehulled soybean meal and other plant materials, provided 40% crude protein, 0.7% phosphorus, 1.5% calcium, and 4,000 IU of supplemental cholecalciferol per kg of diet. Supplements of inorganic phosphorus significantly improved growth, feed utilization, and bone ash content. Inorganic phosphorus supplementation up to 0.6% of the diet increased growth rate and bone ash content; additions beyond this level had little further effect. This study suggests that when young salmon are fed diets containing 0.7% phosphorus from plant sources, the minimum requirement for supplemental inorganic phosphorus is approximately 0.6% of the diet.

Phosphorus flux through fishes: With 2 figures and 3 tables in text

Abstract: (1975). Phosphorus flux through fishes. SIL Proceedings, 1922-2010: Vol. 19, No. 3, pp. 2478-2484.

Zinc phosphate granules in tissue surrounding the midgut of the barnacle Balanus balanoides

Abstract: The chemical composition of inorganic granules found in parenchyma cells surrounding the midgut of adult Balanus balanoides (L.) was determined. X-ray microanalysis indicated the presence of magnesium, phosphorus, potassium, calcium, iron and zinc in the granules. A quantitative analysis of granule-rich pellets isolated from the midguts of adult barnacles showed that the granules were composed mainly of zinc phosphate, the remaining elements being minor constituents only.

Liquid phase epitaxy of GaP by a temperature difference method under controlled vapor pressure

Abstract: A series of experiments have been done in which the properties of GaP grown by liquid phase epitaxy (LPE) have been varied by providing an additional source of phosphorus via the vapor phase. The quality of the crystals, as judged from gross defect features observed in etched cross sections, is a function of the amount of phosphorus added to the vapor phase.