Showing papers on "Phosphorus published in 1983"

Sensitive method for the rapid determination of phytate in cereals and cereal products

Abstract: A rapid method is described for the colorimetric determination of 1.5–15 μg phytate phosphorus in concentrations as low as 3 μg ml−1 in extracts of cereal grains and cereal products. The phytic acid is precipitated with an acidic iron-III-solution of known iron content. The decrease of iron in the supernatant is a measure for the phyticacid content.

The acquisition of phosphorus byLupinus albus L.: III. The probable mechanism by which phosphorus movement in the soil/root interface is enhanced

Abstract: SummaryLarge quantities of citrate ions have been shown to be secreted by the roots ofLupinus albus. It is postulated that these react in the soil to form ferric hydroxy phosphate polymers which diffuse to the root surface where they are degraded by the action of reducing agents in the presence of an Fe II uptake mechanism balanced by hydrogen ion secretion. Some known chemical behaviour of Fe III and citrate which supports this postulate is reviewed. Evidence is also presented which suggests that much of the Fe absorbed circulates within the root system and is subsequently precipitated.

A mechanistic model for describing the sorption and desorption of phosphate by soil

Abstract: Summary A model of phosphate reaction is constructed and its output compared with observations for the sorption and desorption of phosphate by soil. The model has three components: first, the reaction between divalent phosphate ions and a variable-charge surface; second, the assumption that there is a range of values of surface properties and that these are normally distributed; third, the assumption that the initial adsorption induces a diffusion gradient towards the interior of the particle which begins a solid-state diffusion process. The model closely describes the effects on sorption of phosphate of: concentration of phosphate, pH, temperature, and time of contact. It also reproduces the effects on desorption of phosphate of: period of prior contact, period and temperature of desorption, and soil: solution ratio. The model is general and should apply to other specifically adsorbed anions and cations. It suggests that phosphate that has reacted with soil for a long period is not ‘fixed’ but has mostly penetrated into the soil particles. The phosphorus can be recovered slowly if a low enough surface activity is induced.

Spectrophotometric determination of phosphate in river waters with molybdate and malachite green

Abstract: On the basis of the coloration formed with molybdate and malachite green in aqueous solution, trace amounts of phosphate were determined. The molar absorptivity was 7.8 × 104 l mol–1 cm–1 at 650 nm. The absorbance of the reagent blank was about 0.02, and its relative standard deviation was less than 10%. The recommended concentration range of phosphorus was 0.1–5 µg and the limit of detection was 0.01 µg of phosphorus. The sample solution was acidified with sulphuric acid and heated in a water-bath above 90 °C for 40 min, and subsequently it was coloured with molybdate and malachite green. The colour was stabilised by adding poly(vinyl alcohol). The method was applied to the determination of parts per billion (109) amounts of phosphorus in river and tap waters; the relative standard deviation was less than 4% and the recovery was 95–101%.

Interactions of vesicular‐arbuscular mycorrhizal infection and heavy metals in plants

Abstract: SUMMARY Leeks were grown on a γ-irradiated soil selected for its low copper status, in a factorial experiment with additions of phosphorus and copper, and with or without inoculation with Glomus mosseae. There was no response in growth to added phosphorus, but responses to added copper and to inoculation. The results indicate that an infection with mycorrhizal fungi can increase the supply of copper to the host plant, in conditions where increased phosphorus nutrition does not increase dry weight. It is suggested that copper is absorbed and translocated by mycorrhizal hyphae in a manner analogous to that which occurs for phosphorus.

Changes in organic and inorganic phosphorus composition of two grassland soils and their particle size fractions during 60–90 years of cultivation

Abstract: Summary Changes are reported in the chemical and biological composition of soil phosphorus (P) in a Black Chernozemic silt loam (Blaine Lake Association) and a Dark Brown Chernozemic sandy loam (Bradwell Association) during 60–90 years of cultivation Cultivated and adjacent uncultivated soils were sampled, separated into particle size fractions by physical dispersion and the fractions subjected to a sequential chemical extraction to remove several forms of inorganic phosphorus (Pi) and organic phosphorus (Po) In the uncultivated Bradwell soil significant amounts (7%) of secondary (NaOH extractable) Pi forms were associated with high levels of labile (bicarbonate and resin extractable) Pi These secondary Pi forms, which were concentrated in the finer particle size fractions (<2μm), contributed to the P loss during cultivation of the coarse textured Bradwell soil, whereas all P loss in the Blaine Lake soils was due to Po losses alone Sulphuric acid extractable P (thought to be mainly apatites) accumulated in both soils under cultivation, particularly in the coarse silt (50–5 μm) fraction Labile P fractions were greatly reduced during cultivation, indicating a significant reduction in available P and P fertility of cultivated soils This reduction in P fertility was closely tied to soil organic matter losses

Stoichiometry of carbon, nitrogen, and phosphorus in marine particulate matter

Abstract: Particulate carbon, nitrogen, and phosphorus were determined in the Atlantic, Indian, and Antarctic oceans and the Mediterranean Sea. Although the regions differ in their hydrology, the slopes of the regression lines between POC and PON (mean value = 5.6 by atoms) vary P lines in the region. Below the euphotic layer the particle content falls off strongly, but there is no important change in the slopes of the regression lines, which are close to the Redfield ratios. The percentage of refractory carbonaceous material increases with depth. The regional variations are lower than in surface waters.

Phosphorus and nitrogen nutritional status of a northern australian mangrove forest

Abstract: Three sites along a 400-m transect within a tropical mangrove forest in northern Australia were monitored at monthly intervals for 12 mo to determine mangrove response to soil ammonium or phosphate enrichment. Growth response was monitored by measurement of interpetiolar stipule fall, a litter fall component which has been found to be highly correlated with new leaf appearance. Regression slopes for the cumulative stipule fall-time data for each site (2 replicate catchers per site) were used to estimate average stipule fall rates over the treatment year. These were compared with the rates obtained for the identical catcher pairs from a previous year when no treatment was applied. Similar between-year comparisons for 3 corresponding control sites, with no treatment either year, showed no significant changes in stipule fall rates (p > 0.17 in all cases). At the first treatment site, at low elevation within the intertidal zone, no significant response (p = 0.53) to P enrichment was found. For a higher elevation site, 170 m from the nearest tidal channel edge, a significant (p = 0.017) response to P enrichment was recorded, consistent with previous findings of chronically low soil extractable P at the higher elevation sites compared to the lower elevation (edge) sites (5 vs. 14 pg P g-'). A significant response (p = 0.018) to soil ammonium enrichment was found at the third (edge, low elevation) site. As the average soil ammonium level at this site was slightly but significantly higher than for all other sites, it appears that nitrogen limitation is common throughout with phosphorus limitation also evident at the higher elevation areas. Foliar analyses showed that mature Rhizophora leaf nitrogen and phosphorus levels were highly significantly correlated with average soil ammonium and extractable phosphorus respectively. Mature leaves are therefore likely to be useful indicators of mangrove forest nutritional status in remote area surveys. Newly formed leaves showed much higher N and P levels and the leaf parameters showed a complex set of correlations with other soil factors such as redox potential and salinity.

Coprecipitation of phosphate with calcite in a naturally eutrophic lake

Abstract: Phosphorus-rich deposits of Eocene volcanic rock have caused some lakes in the interior of British Columbia to become eutrophic without direct human influence. In Black Lake the soluble reactive phosphorus (SRP) usually exceeds 250 pg Pmliter-‘. When calcite precipitation occurred during blooms of Aphanizomenon, SRP was completely removed from the photic zone. In blooms with no calcite formation, SRP changed little. These observations were replicated by splitting the lake with a curtain. Calcite precipitation was also observed several times in four large enclosures (limnocorrals). The subsequent disappearance of phosphatc was correlated with an increase in pII and a reduction of Ca and alkalinity and not necessarily with primary production or algal biomass. Black Lake is a hypertrophic lake that is naturally enriched in phosphate derived from nearby volcanic rock. The drainage basin is uninhabited, so that Black Lake provides an opportunity to study eutrophication processes without high loadings of organic and toxic wastes. The soluble reactive phosphate (SRP) levels in the inlet stream and the adjoining Black and Yellow Lakes usually exceed 250 ,zg Pliter-‘. These high SRP levels allow direct observation of phosphorus biogeochemistry that previously has only been inferred from laboratory studies. The only major change in SRP concentration occurs early in August during a dense bloom of Aphanixomenon flos-aquae (surface Chl a: 150 pg. liter-l). -Calcium carbonate precipitation induced by the Aphanixomenon bloom appeared to be responsible for the removal of SRP by a coprecipitation reaction. We thank A. Tautz for assistance in 1979, especially for providing laboratory analysis. 0. Smith and S. Liptak provided occasional assistance. D. Nuttley did the chlorophyll cl analysis. W. H. Mathews provided advice on the Okanagan geology. A. Mudroch did the sediment analysis. K. Burnison, J. Barica, and K. Kelts reviewed the manuscript.

The influence of elevated nitrate concentration on rate of leaf decomposition in a stream

Abstract: SUMMARY. 1 Leaf decomposition was compared in two streams at the Coweeta Hydrologic Laboratory, North Carolina. U.S.A. One stream drains an undisturbed hardwood watershed, while the other drains a successional watershed subject to an insect outbreak. The successional watershed has elevated nitrate concentrations in the streamwater. 2 Both black locust (Robinia pseudo-acacia) and sweet birch (Betula lenta) leaf litter decomposed 2.8 times more rapidly in the stream with high nitrate concentrations. 3 The more rapid decay rates appeared to be partly due to accelerated microbial processing in response to nitrate enrichment, because microbial biomass (as ATP) was higher in the nitrate-enriched stream. 4 At each point in time, nitrogen and phosphorus content of the litter was lower in the high nitrate stream; however, there was no significant difference in nitrogen or phosphorus content at the same state of leaf decay in the two streams.

Secondary succession following slash and burn agriculture in north-eastern india

Abstract: SUMMARY (1) The accumulation of elements by vegetation and their rate of uptake and release through litterfall were determined in stands developed during 20 years after shifting agriculture. The concentrations of nitrogen, phosphorus and potassium were higher in the living aerial biomass than in the litter. Trees were found to have a high concentration of calcium, a bamboo of potassium, and herbaceous species of phosphorus. (2) The elements in the above-ground living biomass increased linearly with increase in the age of the fallow until, in the 20-year old fallow, the densities were (g m-2): 49, nitrogen; 6, phosphorus; 138, potassium; 44, calcium; and 23, magnesium. In fallows 10-20 years old, bamboo alone contained 40-45% of the nitrogen, 44-49% of the phosphorus, 54-60% of the potassium, 17-20% of the calcium and 35-40% of the magnesium in the total vegetation. (3) The annual rate of accumulation was maximal after 15-20 years for nitrogen (2-5 g m-2 year-'), 10-15 years for potassium (8. 1 g m-2 year-'), and during the first year for phosphorus (0.4 g m-2 year-1). Potassium showed the highest rate of accumulation in different fallows and was 2.5- to 4.5-fold higher than calcium and 3- to 14-fold higher than magnesium. (4) The enrichment quotient (the weight of an element in the vegetation divided by its rate of uptake) was higher for phosphorus and potassium than for nitrogen, calcium and magnesium, indicating the rapid rate of accumulation of phosphorus and potassium in the standing biomass. The density of elements in the soil was minimal in 5-10 year old fallows. The annual return of elements through litterfall increased with the age of the fallow during the 20 years of study.

Release of Phosphorus from Phytate by Natural Lactic Acid Fermentation

Abstract: Natural lactic acid fermentation of corn significantly reduced phytate levels and thus increased the amount of Fiske-Subbarow positive phosphorus (free). Sixteen bacterial strains isolated from a natural lactic fermentation of corn meal had active phytases.

Physiological changes in, and phosphate uptake by potato plants during development of, and recovery from phosphate deficiency

Abstract: The development of phosphate deficiency (P-stress) was observed in rooted sprouts of Solanum tuberosum L. cv. Desiree growing in solutions without phosphate. Shoot growth was inhibited by P-stress within 3 to 5 days of terminating the phosphate supply, while significant effects on root growth were not recorded until 7 to 9 days. Thus, the shoot:root dry weight ratio decreased from 4.3 to 2.6 over a 10-day period. Growth in the absence of an exogenous phosphate supply progressively diluted the phosphorus in the plant. The proportional decrease in concentration was similar in roots and shoots over a 7-day period, even though the former were growing more quickly. The potential for phosphate uptake per unit weight of root increased rapidly during the first 3 days of P-stress. When the plants were provided subsequently with a labelled, 1 mol m−3 phosphate solution, the absorption rate was 3 to 4-fold greater than that of control plants which had received a continuous phosphate supply. The increased rate of uptake by P-stressed plants was accounted for by an increase (3-fold) in the Vmax of system 1 for phosphate transport and by a marked increase in the affinity of the system for phosphate (decrease in Km). In the early stages of P-stress, before marked changes in growth were measured, the proportion of labelled phosphate translocated to the shoots increased slightly relative to the controls when a phosphate supply was restored. In the later stages of stress a greater proportion was retained in the root system of P-stressed plants than in that of controls. In plants with roots divided between solutions containing or lacking a phosphate supply, the increased absorption rate was determined by the general demand for phosphate in the plant and not by the P-status of the particular root where uptake was measured. By contrast, the poportion translocated was strongly dependent on the P-status of the root. The restoration of a phosphate supply to P-stressed plants was marked by a rapid increase in the P concentration in snoots and roots which returned to levels similar to unstressed controls within 24 h. The enhanced uptake rate persisted for at least 5 days, resulting in supra-normal concentrations of P in both shoots and roots, and in the formation of extensive necrotic areas between the veins of mature leaves. Autoradiographs showed accumulations of 32P in these lesions and at the points where guttation droplets formed on leaves.

Nutrient Loading Estimates for Lakes

Abstract: The nitrogen and phosphorus loads to a waterbody may be reliably estimated on the basis of the waterbody's watershed land use pattern and the nitrogen and phosphorus export coefficients for each dominant type of land use. Good agreement was found in a comparison between the nitrogen and phosphorus export coefficients developed in this study and the measured amounts of nitrogen and phosphorus transported to 38 U.S. waterbodies. Good agreement was also found between the load estimated by the Vollenweider model relating the mean annual in‐lake and inflow phosphorus concentrations of a waterbody, and the measured amounts of phosphorus that actually entered the 38 waterbodies.

Phosphatase production by mycorrhizal fungi

Abstract: Sheathing mycorrhizal fungi have been shown to possess phosphatase enzymes which can hydrolyse inositol hexaphosphate. In a range of mycorrhizal fungi, this activity was often greater than in two common decomposer basidiomycetes. Mycorrhizal birch and pine roots both produce phosphatases. In birch production is inversely related to the inorganic phosphorus concentration in the growth medium. Mycorrhizas reduce phosphatase activity compared with non-mycorrhizal plants.

The effect of nitrate and phosphate on the vesicular-arbuscular mycorrhizal infection of lettuce

Abstract: SUMMARY The application of increasing amounts of nitrate resulted in higher levels of vesicular-arbuscular mycorrhizal infection in lettuce roots inoculated with Glomus mosseae. This effect was found at three phosphate levels. The application of nutrient solutions containing different concentrations of nitrate and phosphate resulted in different nitrogen and phosphorus levels in the roots. At high concentrations of phosphorus in the roots, infection was inhibited, but at low concentrations the infection level appeared to be related to the nitrogen content of the host tissue. Mycorrhizal infections in low-nitrogen treatments were poorly developed with very few arbuscules and intercellular hyphae. Two methods of estimating infection (gridline intersect and yield of glucosamine) were compared.

Phosphorus and nitrogen in coral reef sediments

Abstract: The occurrence of P and N in the sediments has been investigated on Davies Reef in the central region of the Great Barrier Reef Complex. Concentrations of inorganic P and N in the water were typical of nutrient-depleted tropical surface water. Carbonate sediments were found to contain a uniform pool of P (300 ppm by wt), principally in the form of inorganic phosphate. The interstitial water of the surface layer of sediment contained micromolar concentrations of inorganic P and even higher concentrations of inorganic N, principally as ammonium. These nutrient concentrations should allow high rates of uptake of N and P by epilithic algae. Arsenate concentrations were considered too low to compete significantly with the uptake of available phosphate into algae. The presence of ammonium and soluble P was associated with anaerobic redox potentials in the sediments just below the surface. Soluble phosphorus was in equilibrium with a small, rapidly exchangeable fraction of the sedimentary pool of inorganic phosphate. Analyses of P in growing tips of Halimeda and corals (which supply more than half of reef sediments) suggested that the skeletons provide a biological mechanism for the replenishment of at least some of the sedimentary pool. Ratios of C:N:P for a selection of benthic algae were used as a preliminary indicator of their N and P status.

Continuous ammonium enrichment of a woodland stream: uptake kinetics, leaf decomposition, and nitrification

Abstract: 1 In order to test for nitrogen limitation and examine ammonium uptake by stream sediments, ammonium hydroxide was added continuously at concentrations averaging 100 μg1-1 for 70 days to a second- order reach of Walker Branch, an undisturbed woodland stream in Tennessee. 2 Ammonium uptake during the first 4h of addition corresponded to adsorption kinetics rather than to first-order uptake or to Michaelis- Menten kinetics. However, the calculated adsorption partition coefficient was two to four orders of magnitude greater than values reported for physical adsorption of ammonium, suggesting that the uptake was largely biotic. 3 Mass balance indicated that the uptake of ammonium from the water could be accounted for by increased nitrogen content in benthic organic detritus. Nitrification, inferred from longitudinal gradients in NO3, began soon after enrichment and increased dramatically near the end of the experiment. 4 Both ammonium and nitrate concentrations dropped quickly to near background levels when input ceased, indicating little desorption or nitrification of excess nitrogen stored in the reach. 5 There was no evidence of nitrogen limitation as measured by weight loss, oxygen consumption, phosphorus content, and macroinvertebrate density of red oak leaf packs, or by chlorophyll content and aufwuchs biomass on plexiglass slides. A continuous phosphorus enrichment 1 year earlier had demonstrated phosphorus limitation in Walker Branch.

Phosphorus, soluble carbohydrates and endomycorrhizal infection

Abstract: The effect of phosphorus supply on concentrations of soluble carbohydrate within roots and on the development of mycorrhizas on subterranean clover was examined in two glasshouse experiments. Where increasing phosphorus supply decreased the percentage of root length converted to mycorrhizas, it also decreased the concentrations of soluble carbohydrates within roots. Shading, defoliation and low root temperatures also decreased both the percentage of root length infected and concentrations of soluble carbohydrate within roots. The percentage of root length infected was closely correlated with concentrations of soluble carbohydrates within roots irrespective of the treatment used to vary these concentrations. Small additions of phosphorus to severely deficient plants increased the percentage root length infected possibly by stimulating the growth of the mycorrhizal fungus.

Chemical and Radiotracer Measurements of Phosphorus Uptake by Lake Plankton

Abstract: Either chemical or radioisotope methods can be used to measure the maximum uptake velocity for phosphorus in lake water but neither can measure uptake at ambient concentrations. Chemical estimates at ambient concentrations are insensitive and the isotope method provides the uptake rate constant only. By multiplying the uptake rate constant by the ambient phosphate concentration one obtains an estimate for phosphorus influx, but reliable estimates for ambient phosphate concentrations are still unattainable. At added phosphate levels even up to 10 μg P∙L−1, the isotope method overestimates net phosphate uptake because of release of phosphate from the plankton. Influx and efflux are practically equal under steady state conditions, and during periods of phosphate limitation a net uptake of phosphorus occurs only when there is an increase in the phosphorus supply. The uptake of phosphate is predominantly by small cells at low concentrations of added phosphate and by larger cells at the higher enrichments. This...