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PubMed1981

Availability of phosphorus contained in poultry litter for lambs.

Percentage net phosphorus availability (NPHA) and set phosphorus utilization (NPHU) of the phosphorus contained in a heat-sterilized poultry litter (PL) as compared to feed grade dicalcium phosphate (DCP) for lambs was assessed by the "slope" method. The method was based on the evaluation of the function of apparent phosphorus absorption (NPHA), or retention (NPHU), on phosphorus intake. Nitrogen retention was also evaluated. Plasma inorganic phosphorus concentration as a function of phosphorus intake was evaluated and compared to NPHA and NPHU. The percentage of NPHA was found to be 63.7 and 39, and that of NPHU was 63 and 38 for the phosphorus supplied by DCP and PL, respectively. Thus, the NPHA or NPHU for the phosphorus contained in PL is 60.9 and 60.3% of that of DCP, respectively. The slope ratio between the two phosphate supplements as observed for plasma inorganic phosphorus concentrations was similar to those found for NPHA and NPHU but the coefficient of variation was 5 times higher. Nitrogen digestibility was not affected by the level of phosphorus in the diets. Correlation between nitrogen retention and NPHA or NPHU was, however, significant (P less than 0.05). The slopes of dependence of N retention upon phosphorus intake were 2.81 and 1.6 (P less than 0.05) for DCP and PL treatments, respectively, and the ratio between the slopes was 0.57, close to the ratio of NPHU in PL to DCP-supplemented diets.

Animal Feed↗
PubMed2001

Induction of a major leaf acid phosphatase does not confer adaptation to low phosphorus availability in common bean.

Acid phosphatase is believed to be important for phosphorus scavenging and remobilization in plants, but its role in plant adaptation to low phosphorus availability has not been critically evaluated. To address this issue, we compared acid phosphatase activity (APA) in leaves of common bean (Phaseolus vulgaris) in a phosphorus-inefficient genotype (DOR364), a phosphorus-efficient genotype (G19833), and their F(5.10) recombinant inbred lines (RILs). Phosphorus deficiency substantially increased leaf APA, but APA was much higher and more responsive to phosphorus availability in DOR364 than in G19833. Leaf APA segregated in the RILs, with two discrete groups having either high (mean = 1.71 micromol/mg protein/min) or low (0.36 micromol/mg protein/min) activity. A chi-square test indicated that the observed difference might be controlled by a single gene. Non-denaturing protein electrophoresis revealed that there are four visible isoforms responsible for total APA in common bean, and that the difference in APA between contrasting genotypes could be attributed to the existence of a single major isoform. Qualitative mapping of the APA trait and quantitative trait loci analysis with molecular markers indicated that a major gene contributing to APA is located on linkage group B03 of the unified common bean map. This locus was not associated with loci conferring phosphorus acquisition efficiency or phosphorus use efficiency. RILs contrasting for APA had similar phosphorus pools in old and young leaves under phosphorus stress, arguing against a role for APA in phosphorus remobilization. Our results do not support a major role for leaf APA induction in regulating plant adaptation to phosphorus deficiency.

Acid Phosphatase↗
PubMed1989

Physiologic regulation of the serum concentration of 1,25-dihydroxyvitamin D by phosphorus in normal men.

We asked this question: in normal humans, is either a normal dietary intake or normal serum concentration of phosphorus a determinant of the serum concentration of 1,25(OH)2D? In seven normal men whose dietary phosphorus was decreased from 2,300 to 625 mg/d, each intake for 8-9 d, under strictly controlled, normal metabolic conditions, we measured serum concentrations of 1,25(OH)2D daily, and concentrations of phosphorus hourly throughout a 24-h period, before and after restriction. Decreasing dietary phosphorus induced: (a) a 58% increase in serum levels of 1,25(OH)2D; (b) a 35% decrease in serum levels of phosphorus measured in the afternoon; (c) a 12% decrease in the 24-h mean serum level of phosphorus; but, (d) no decrease in morning fasting levels of phosphorus. Serum concentrations of 1,25(OH)2D varied inversely and significantly with 24-h mean concentrations of phosphorus (r = -0.77, P less than 0.001). When these data are combined with those of our prior study in which dietary phosphorus was varied over an extreme range, the relationship between serum levels of 1,25(OH)2D and 24-h mean serum levels of phosphorus is even stronger (r = -0.90, P less than 0.001). In the aggregate, the results demonstrate that in normal men, dietary phosphorus throughout a normal range and beyond, can finely regulate the renal production and serum concentration of 1,25(OH)2D, and provide evidence that this regulation is mediated by fine modulation of the serum concentration of phosphorus.

Adult↗
PubMed1992

Why is the phosphorus content of human milk exceptionally low?

The phosphorus supply of children and adults is adequate, and usually in excess. Therefore, it is surprising that in breast-fed infants phosphorus intake is very low. This is very rare among mammals. In infants three pathophysiological mechanisms argue in favour of a low, but adequate phosphorus intake in the presence of a balanced ratio of calcium to phosphorus. A low intestinal phosphorus concentration is an essential condition of an acid pH of the faeces, inhibiting the growth of potentially pathogenic germs. Owing to the characteristic renal physiology of the newborn, a small metabolic phosphorus surplus results in a high serum phosphorus level, a well-known risk factor for several disorders, e.g. hypocalcaemic tetany. During infections, impairment of intestinal calcium but not of phosphorus absorption results in an increased phosphorus and renal net acid excretion. Considering the low renal capacity for acid excretion in newborns, a high intake of calcium and phosphorus is a risk factor for the development of metabolic acidosis. It is thought that all three pathophysiologic mechanisms were effective in the biochemical evolution of humans, selecting women with a low phosphorus milk and infants with a constant high intestinal absorption rate of phosphorus.

Acid-Base Equilibrium↗
PubMed2005

[Analysis on the removal efficiency of phosphorus in some substrates used in constructed wetland systems].

Constructed wetlands are widely used to purify wastewater in some developing countries. As filter substrates in such wetland, these substrates play important role on removal of pollutants from wastewater. Selecting suitable substrates is one of the effective ways to improve the performance of constructed wetland on treating wastewater. In this study the phosphorus adsorption capacities of sand, zeolite, vermiculite, two clay soils, two industrial by-products named steel slag and fly ash are examined for their potential use as substrate in constructed wetland. Both Freundlich and Langmuir adsorption isotherms are very fit for describing the adsorption characteristics of these substrates. Two industrial by-products including steel slag and fly ash have higher phosphorus adsorption capacity, which had 50490 and 17934 mg x kg(-1) respectively. Followed vermiculite, two clay soils named yellow cinnamon and xiashu loess with phosphorus adsorption capacity of 3473, 1893.7 and 1582 mg x kg(-1) respectively. The zeolite and sand had the least phosphorus adsorption capacity with 813.7 and 302 mg x kg(-1) respectively. The experiments on purifying phosphorus from synthesize domestic sewage using these substrates also demonstrate this conclusion. The ability of removal phosphorus of these substrates have closely relationship with their makeup and chemical properties such as pH, total calcium and reactive calcium, reactive Fe, Al including poorly coastal and amorphous Fe, Al oxide. The steel slag and fly ash with higher reactive Ca, such as calcium oxide, have better adsorption capacity of phosphorus than other substrates, and the substrates which contained more reactive Fe also have a better ability of adsorption phosphorus than others. To assess the environmental risk for using these substrates above, the phosphorus de-sorption characteristics of these substrates are also studied. The process of phosphorus desorption quickly reached equilibrium in no more than 4 hours in the experiments, the ratio of desorption and adsorption of phosphorus in substrates above is lower except sand. To take suitable measures to manage substrates above, the risk of pollution of phosphorus form these substrates will be controlled.

Adsorption↗
PubMed2006

[Effects of soil phosphorus level on morphological and photosynthetic characteristics of Ageratina adenophora and chromolaena odorata].

In this paper, a comparative study was made on the growth, morphology, biomass allocation, and photosynthesis of two invasive plant species Ageratina adenophora and Chromolaena odorata under five soil phosphorus levels, aimed to know how the test plant species acclimate to the changes of soil phosphorus level, evaluate which plant traits were associated with the invasiveness of the two species, and know whether the increased level of soil phosphorus could facilitate their invasion. The results showed that the two species had considerable phenotypic plasticity and ? phosphorus acclimation ability. At low phosphorus levels, their root mass ratio increased, which could enhance the nutrient capture ability, while at high phosphorus levels, their specific leaf area, maximum net photosynthetic rate, light saturation point, and chlorophyll and carotenoid contents per unit area were high, and the assimilative capacity and area increased, which could facilitate their carbon gain. A. adenophora had higher phosphorus acclimation ability than C. odorata. With the increase of phosphorous level, the relative growth rate, total biomass, branch number, leaf area index, and maximum net photosynthetic rate of the two species increased significantly, and most of the parameters were not decreased significantly under over-optimal phosphorus level. The two species could grow better under high phosphorus levels which were usually excessive and/or harmful for most native species, and enhanced soil phosphorus level might promote their invasion. At high phosphorus levels, the two invasive plant species might shade out native species through increasing their plant height, branch number, and leaf area index. The two species could maintain relatively high growth rate under high phosphorus levels in dry season when native plant species almost stopped growing. The ability that the invasive plant species could temporally use natural resources which native plant species could not use was also associated with their invasiveness.

Ageratina↗
PubMedDate not supplied

[A study of serum phosphorus and renal phosphate excretion in children of different age groups].

To further elucidate the data of high serum phosphorus concentration reported for foreign children, this study compared the values of serum phosphorus concentration in ethnic Chinese children with foreigners' results, and investigated the potential causes of high serum phosphorus concentration. This study included 33 healthy term male neonates from 2-3 days to 5-7 days old, 1,094 children of 6-18 years old (elementary school-senior high school) and 62 adults. A total of 1,189 persons were studied. Value of serum phosphorus concentration showed no significant difference between boys and girls, and no age dependency; there was notable change in serum phosphorus concentration in growing children of different ages. The mean values of serum phosphorus concentration of neonates aged 2-3 days and 5-7 days (7.20 mg/dl and 7.65 mg/dl, respectively) were the highest; boys aged 6-11 years 5.15-5.50 mg/dl and girls aged 6-11 years 5.14-5.28 mg/dl were the second; boys aged 12-18 years 4.31-4.94 mg/dl and girls aged 12-18 years 4.44-4.96 mg/dl were the lowest. These findings are similar to the conclusions of foreign reports that the older the subjects of the study, the less their serum phosphorus concentration. The maximal transport rates of tubular phosphate reabsorption were determined from a Walton-Bijvoet nomogram using the side-rule method they recommend. The renal phosphate threshold concentration of neonates aged 2-3 days 8.41 mg/100 ml GFR and 5-7 days 7.76 mg/dl GFR was also the highest; boys aged 6-11 years 5.84-6.32 mg/dl GFR and girls aged 6-11 years 5.82-6.10 mg/dl GFR and 5.44-6.10 mg/dl GFR was the second; adult males 3.51 mg/dl GFR and adult females 3.62 mg/dl GFR was the lowest. Increased intestinal absorption of phosphorus, low GFR and low clearance of phosphorus might be the contributing factors to cause high serum phosphorus concentration. Although high renal phosphate threshold capacity is important, increased absorption of phosphorus by G-I tract seems to be another factor in accordance with the need of phosphorus of the growing body cells.

Adolescent↗
PubMedDate not supplied

II. Quantitative aspects of phosphorus absorption in ruminants.

Phosphorus absorption in ruminants was analysed from a database described in a previous article. For common values of ingested phosphorus (2.5-5.0 g x kg(-1) of DM), 0.73 of dietary phosphorus is absorbed. The remaining variability is probably due to phosphorus quality. Phosphorus absorbed from silage, cereal, cereal by-products and hay differs greatly. The current true absorption coefficient used to calculate daily phosphorus supply is a constant value in the current systems and often it underestimates the true absorption resulting in an excess of phosphorus being supplied in the diets. Adjusting the true absorption coefficient values requires better characterisation of the phosphorus supplied by each feedstuff. Dietary influences (phytate phosphorus, crude fibre, etc.) were investigated but trials assessing the ration effect on phosphorus absorption are lacking. Since rumen microbes have specific phosphorus requirements, particularly for cell-wall degradation, the feedstuffphosphorus availability for the rumen ecosystem is discussed.

Animal Feed↗
PubMed1991

Calcium metabolism in Great Dane dogs fed diets with various calcium and phosphorus levels.

The influence of dietary calcium on calcium metabolism was investigated in growing dogs that reach an adult body weight similar to that of humans. Seven groups of dogs (n greater than or equal to 5) were raised on a diet with a composition meeting the National Research Council (NRC) requirements (1974), but differing in calcium content, with or without a constant ratio to phosphorus. Control dogs fed 1.1% calcium and 0.9% phosphorus (all on a dry matter basis) were fed ad libitum (n = 10) or in restricted amounts (n = 6); dogs fed high calcium (3.3%) diets received either 0.9% phosphorus (n = 6) or 3.0% phosphorus (n = 6); dogs fed low calcium (0.55%) diets received either 0.9% phosphorus (n = 5 + 6) or 0.5% phosphorus (n = 8). Food intake, circulating total calcium and inorganic phosphorus concentrations and calcium metabolism, with 45Ca kinetics, were studied at 8, 14, 20 and 26 wk of age. Except for the difference in food intake in two groups at 14 wk (i.e., 0.55% calcium-0.9% phosphorus higher and 3.3% calcium-0.9% phosphorus lower, respectively, than the controls) no differences were noticed during the rest of the study. The mean plasma calcium concentrations did not differ between groups during the studies, whereas that of inorganic phosphorus revealed temporal aberrations in two groups. An absorption coefficient alpha of 45-66% was found for the control group. High and low calcium diets gave rise to values of 23-43% and 70-97%, respectively, for alpha irrespective of the phosphorus content of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1995

Increasing phosphorus intake reduces urinary concentrations of magnesium and calcium in adult ovariectomized cats fed purified diets.

We assessed the phosphorus requirement of adult cats and the relationship between phosphorus intake and the fecal and urinary excretion of calcium, magnesium and phosphorus. Female cats (ovariectomized at the onset of sexual maturity) were fed purified diets containing 4.6, 9.2, 18.4 or 27.7 mmol phosphorus/MJ in a 4 x 4-wk crossover study. During the experiment, balance studies were performed and blood samples were taken. A dietary level of 4.6 mmol phosphorus/MJ was found to be sufficient to maintain phosphorus balance and normal plasma concentrations of phosphorus in the adult ovariectomized cats. Increasing levels of dietary phosphorus in the form of NaH2PO4.2H2O caused lower urinary pH values, lower urinary concentrations of calcium and magnesium, and higher urinary concentrations of phosphorus. When dietary levels of phosphorus were raised, the percentage of apparent absorption of magnesium was lower, whereas that of phosphorus was higher. Although it could be predicted that dietary phosphorus levels higher than the National Research Council recommendation of 9.2 mmol/MJ markedly reduced urinary struvite saturation, these higher levels are discouraged because they are associated with lower plasma phosphorus concentrations and creatinine clearance.

Absorption↗
PubMed1996

Direct effect of phosphorus on PTH secretion from whole rat parathyroid glands in vitro.

Phosphorus retention is an important factor in the development of hyperparathyroidism secondary to renal failure. In vivo manipulation of phosphorus is associated with changes in serum calcium and calcitriol levels which in turn can modify parathyroid hormone synthesis and secretion. The present in vitro study evaluates whether high extracellular phosphorus has a direct effect on parathyroid hormone secretion. Fresh rat parathyroid glands were incubated in a media with phosphorus concentrations of 1, 2, 3, and 4 mM and subsequently exposed to calcium levels ranging from 0.4 to 1.35 mM. In 1.25 mM calcium, the parathyroid hormone secretion rate was similar in 1 and 2 mM phosphorus; however, a phosphorus concentration of 3 and 4 mM produced a 3- and 4-fold increase in the parathyroid hormone secretion, respectively, as compared with 1 mM phosphorus. While in 1 or 2 mM phosphorus an increase in calcium from 0.6 to 1.35 mM reduced parathyroid hormone secretion to 37%, in 4 mM phosphorus the same increase in calcium only inhibited parathyroid hormone secretion to 75%. Furthermore, the addition of arachidonic acid 20 microM, a substrate for inhibitory intracellular signal pathway, to the 4 mM phosphorus-1.35 mM calcium incubation media reduced the parathyroid hormone secretion to 34.5% (p < 0.05). In conclusion, our results indicate that in vitro, high phosphorus directly increases parathyroid hormone secretion.

Analysis of Variance↗
PubMed1994

The effects of high phosphorus intake on calcium homeostasis.

Survey data confirm that the dietary pattern of many American women who are at high risk of developing osteoporosis is typically high in phosphorus and low in calcium. The imbalance between calcium and phosphorus intake may become more pronounced with continued changes in food preferences and the growing use of phosphorus-containing food additives. Recent studies in young women have shown that a high phosphorus diet moderately low in calcium results in a mild secondary hyperparathyroidism that persists over 4 weeks. Plasma levels of calcitriol did not change despite changes in PTH and serum ionized calcium. Studies on men have shown that dietary phosphorus at levels within the normal range of intakes can affect the renal production and serum concentration of calcitriol. High phosphorus intakes for ten days reduced their plasma calcitriol levels; a 70% reduction in phosphate intake significantly increased their plasma calcitriol. Thus, several lines of evidence indicate that prolonged high phosphorus intake may impair the usual homeostatic mechanisms that come into play when dietary calcium is limited. This, in turn, could impair achievement of maximal bone mass or accelerate bone loss. Although no clinical studies have linked high phosphorus intake with lower bone mass or higher rates of bone loss in humans, this relationship has been demonstrated in animal models. For example, young beagles fed high phosphorus, moderately low calcium diets showed a significant reduction in vertebral bone mass. Current dietary patterns of high phosphorus, low calcium consumption result in persistent changes in calcium regulating hormones that are not conducive to maximizing peak bone mass during growth or slowing the rate of aging bone loss. The net effect of the present dietary pattern on bone status, particularly in teenage and young adult women, needs to be determined. Optimal nutrition early in life, which may include higher calcium and lower phosphorus intakes, together with adequate exercise, may be the most cost-effective approach to the prevention of osteoporotic fractures.

Animals↗
PubMed1993

Characterization of dietary phosphorus-dependent duodenal calcium uptake in vitamin D-deficient chicks.

The effect of dietary phosphorus on intestinal calcium uptake was examined in duodenal cells isolated from vitamin D-deficient chicks. Cells from chicks on a high phosphorus diet accumulated calcium at a rate 38% higher than cells from animals on a normal phosphorus diet. Diet high in calcium did not affect calcium absorption in duodenal cells. The dietary phosphorus effect on calcium absorption was specific. Uptake of alpha-methyl glucose was not altered. Increase in calcium absorption by a high phosphorus diet was not due to a change in cellular energy metabolism nor to the content of phosphorus in cells. Kinetically, a high phosphorus diet increased the Vmax of calcium uptake; the affinity for calcium was unaffected. The effectiveness of dietary phosphorus to enhance the intestinal calcium uptake could also be demonstrated in brush border membrane vesicles. The increase in calcium uptake was not due to an alteration in membrane binding capacity nor to calcium efflux from vesicles. To test the hypothesis that a high phosphorus diet may affect membrane transport by altering phospholipid metabolism in duodenal cells, we examined the phospholipid content in isolated brush border membranes. The content of phosphatidylcholine, phosphatidylserine, phosphatidylinositol and phosphatidylethanolamine was not altered by the high phosphorus diet. These findings suggest that the vitamin D-independent and dietary phosphorus-dependent effect on intestinal calcium absorption was primarily due to a change in the calcium flux at the luminal side of the cells. However, the precise mechanism is still not clear.

Administration, Oral↗
PubMed2003

A new method for characterizing denitrifying phosphorus removal bacteria by using three different types of electron acceptors.

This study investigated the characteristics of denitrifying phosphorus removal bacteria by using three different types of electron acceptors as well as the positive role of nitrite in phosphorus removal process. Denitrifying phosphorous removal bacteria was enriched under anaerobic-anoxic (A/A) condition. To understand A/A sludge better, sludge from two other sources were also studied. These include sludges obtained from a lab-scale anaerobic-anoxic-aerobic (A/A/O) system and a local sewage treatment plant. Three types of possible electron acceptors (oxygen, nitrate and nitrite) were examined for their roles in phosphorus uptake. The results obtained indicated that oxygen, nitrate and nitrite were able to act as electron acceptors successfully. This observation suggested that in addition to the two well-accepted groups of phosphorus removal bacteria (one can only utilize oxygen to take up phosphorus, P(O), while the other can use both oxygen and nitrate, P(ON)), a new group of phosphorus removal bacteria, P(ON(n)), which could use oxygen, nitrate or nitrite to take up phosphorus was identified. The relative population of these three types of bacteria could be calculated from results obtainable from phosphorus uptake batch experiments with either oxygen or nitrate or nitrite as electron acceptor. The results obtained in this study showed that A/A sludge had similar phosphorus removal performance as the A/A/O sludge. However, it has better denitrifying phosphorus removal capability, which was demonstrated by the relative population of the three groups of bacteria. The results also suggested that nitrite was not an inhibitor to phosphorus removal process. Instead, it is an alternative electron acceptor to oxygen or nitrate.

Bacteria↗
PubMedDate not supplied

Effects of the interactions between selenium and phosphorus on the growth and selenium accumulation in rice (Oryza sativa).

The solution culture, paddy soil culture and the simulation experiments in the laboratory were conducted to clarify the interactions between selenium and phosphorus, and its effects on the growth and selenium accumulation in rice. Results revealed that a suitable supply of selenium could promote rice growth and excessive selenium could injure rice plant, causing lower biomass, especially in the roots. The supply of selenite could enhance the selenium contents of rice shoots and roots in solution culture and in soil culture. The selenium concentrations in roots were much higher than those in shoots supplied with the same rates of selenium and phosphorus. The interaction between selenium and phosphorus was evident. When the phosphorus supply increased to meet the needs of plant growth, phosphorus could promote absorption and accumulation of selenium in the shoots. If the phosphorus supply was excessive, phosphorus could inhibit the accumulation of selenium in the shoots at the lower selenite level (2 micromol l(-1)), but could not at the higher selenite level (10 micromol l(-1)). With the supply of phosphate increased, the selenium concentrations in the roots decreased significantly at both selenite levels. The presence of phosphate could decrease Se sorption on the soil surface and increase the selenium concentration in the soil solution. The concentrations of selenium in shoots and roots supplied with 0.08 g kg(-1) phosphorus were lower than those with no phosphorus supplied. With the increase of phosphorus added to 0.4 g kg(-1), the selenium concentration in shoots and roots increased. The effect of phosphorus on the concentration was statistically significant at all three selenium levels.

Absorption↗
PubMed1989

Calcium acetate, an effective phosphorus binder in patients with renal failure.

Calcium salts are increasingly used as phosphorus binders in patients with chronic renal failure. Calcium carbonate is the principal salt presently utilized, however, other calcium salts may be more effective and safer phosphorus binders. Theoretical calculations, in vitro experiments, and in vivo studies in normal subjects have shown calcium acetate to be a more effective phosphorus binder than other calcium salts. This salt has not previously been studied in patients with chronic renal failure. We used a one-meal gastrointestinal balance technique to measure phosphorus absorption, calcium absorption and phosphorus binding in six patients with chronic renal failure. Calcium acetate was compared with calcium carbonate and placebo. Equivalent doses (50 mEq Ca++) of calcium acetate bound more than twice as much phosphorus (106 +/- 23 mg) as calcium carbonate (43 +/- 39 mg) P less than 0.05. When phosphorus binding was factored for calcium absorption, calcium acetate bound 0.44 mEq HPO4 =/mEq absorbed Ca++ compared with 0.16 mEq HPO4 = bound/mEq Ca++ absorbed with calcium carbonate. More efficient phosphorus binding permits serum phosphorus concentration to be controlled with lower doses of calcium salts. The higher phosphorus binding/calcium absorption ratio coupled with a lower dose indicates that less calcium will be absorbed when calcium acetate is used for phosphorus control. Markedly positive calcium balance, hypercalcemia and ectopic calcification should be less likely to occur with this drug than other calcium salts.

Acetates↗
PubMed2001

Extracellular secretion of Aspergillus phytase from Arabidopsis roots enables plants to obtain phosphorus from phytate.

Phosphorus (P) deficiency in soil is a major constraint for agricultural production worldwide. Despite this, most soils contain significant amounts of total soil P that occurs in inorganic and organic fractions and accumulates with phosphorus fertilization. A major component of soil organic phosphorus occurs as phytate. We show that when grown in agar under sterile conditions, Arabidopsis thaliana plants are able to obtain phosphorus from a range of organic phosphorus substrates that would be expected to occur in soil, but have only limited ability to obtain phosphorus directly from phytate. In wild-type plants, phytase constituted less than 0.8% of the total acid phosphomonoesterase activity of root extracts and was not detectable as an extracellular enzyme. By comparison, the growth and phosphorus nutrition of Arabidopsis plants supplied with phytate was improved significantly when the phytase gene (phyA) from Aspergillus niger was introduced. The Aspergillus phytase was only effective when secreted as an extracellular enzyme by inclusion of the signal peptide sequence from the carrot extensin (ex) gene. A 20-fold increase in total root phytase activity in transgenic lines expressing ex::phyA resulted in improved phosphorus nutrition, such that the growth and phosphorus content of the plants was equivalent to control plants supplied with inorganic phosphate. These results show that extracellular phytase activity of plant roots is a significant factor in the utilization of phosphorus from phytate and indicate that opportunity exists for using gene technology to improve the ability of plants to utilize accumulated forms of soil organic phosphorus.

6-Phytase↗
PubMed2006

Field investigation of advanced filtration for phosphorus removal from constructed treatment wetland effluents.

Three sorptive media, blast furnace slag, cement clinker, and gravel were investigated for their capacity to remove phosphorus in a subsurface flow constructed treatment wetland post-treatment filter. Three filters were designed: two containing a mixture of either slag and gravel or clinker and gravel, and one with gravel only as the control filter. They were installed as a demonstration polishing treatment step to a constructed treatment wetland treating residential wastewater collected from 137 mobile home units at the Sunny Creek Estates Mobile Home Park. The filters were commissioned during the summer of the field season, with the data gathering taking place over a period of one year. The slag filter consistently had the lowest outflow dissolved phosphorus concentrations (0.27 +/- 0.08 mg l(-1), n=21), whereas the clinker filter had the highest outflow dissolved phosphorus concentrations (0.72 +/- 0.20 mg l(-1), n=23). The clinker filter performed well below expectations based on previous laboratory investigations, possibly due to lower pH conditions encountered in the field study. All of the filters maintained relatively constant outflow concentrations of phosphorus below 1 mg l(-1), despite varying input conditions and environmental factors such as temperature and phosphorus loading, and the occurrence of net export of phosphorus from the wetland. Net export of phosphorus from the filters occurred in the winter months, which was attributed to the decrease in input phosphorus concentrations below the maintained outflow concentrations (leading to phosphorus desorption), rather than cold temperatures or failure of the filter. Although the exact mechanisms of phosphorus removal are still under investigation, the results from this field study allowed for recommendations to be made for improving phosphorus removal at the Sunny Creek Estates constructed treatment wetland, in addition to providing valuable information for new and existing constructed treatment wetlands in cold climate areas.

Adsorption↗