Soluble organic phosphate

Iron-bound phosphate Calcium-bound phosphate Acid-soluble organic phosphate Sodium hydroxide-extractable phosphorus Fe(OOH) P CaCOj P ASOP NaOH3,-P 0.02 M Ca-NTA/dithionite, pH 7.8-8.0 0.05 M Na-EDTA, pH about 8.0 0.5 M HCI or 0.25 M HjSO (30 min) 2.0 M NaOH (OO C, 30 min)... 

Although overlooked by these and many other authors, another possibility is to use the organic phosphate present in the environment. This chapter sets out to assess how widespread this is in cyanobacteria, algae and bryophytes, and to review the methods involved. The focus is on soluble organic phosphate, because this has been the subject of most studies, though some cyanobacteria may be able to utilize insolu-... 

Plants can absorb some soluble organic phosphates, such as phytin and nucleic acid that may be formed from organic matter, but such substances are so readily attacked by microorganisms that it is doubtful if direct absorption of these phosphates occurs to any appreciable extent in soils. Most of the phosphorus undoubtedly enters the root as the primary orthophosphate ion, H2P04, but a lesser amount may be absorbed as the secondary orthophosphate ion, HP04 . A low pH favors the uptake of the primary form and a higher pH favors the absorption of the secondary ion. Unlike nitrate, which is reduced when utilized by plants, phosphate remains in the oxidized state in organic combinations. 

Acid-soluble organic phosphate ASOP 0.5 M HCI or 0.025 M H2SO4 (30 min)... 

Kates (1955) extended the research of earlier workers on the degradation of PC by plant extracts. The action of phospholipase D was readily measured by the release of choline, but the release of water-soluble organic phosphate and inorganic phosphate was also measured. Spinach leaf extracts were particularly effective in releasing inorganic phosphate. A 15,(XK)-g particulate fraction of leaf homogenate was used for the assay. The pH optimum for phosphate release was 5 it was pointed out that this may reflect the pH optimum for the release of PA, that is, the action of phospholipase D. 

Fig. 6.20A-F. Changes in various phosphate components in the roots (a), shoots (x) and non-axial parts —NAP ( ) of germinated oat seedlings. (A) Fresh weight, (B) Total phosphate, (C) Acid soluble phosphate. In the NAP this is comprised mainly of phytic acid, and in the shoot and root of inorganic phosphate and some acid soluble organic phosphate (but no phytic acid), (D) Nucleic acid phosphate, (E) Lipid phosphate, (F) Protein phosphate. Based on Hall and Hodges, 1966 [58]...

The smallest amount of soluble organic phosphate that can be detected with certainty is about 0.03 /ng-at/liter. 

Air-poUutant effects on neural and sensory functions in humans vary widely. Odorous pollutants cause only minor annoyance yet, if persistent, they can lead to irritation, emotional upset, anorexia, and mental depression. Carbon monoxide can cause death secondary to the depression of the respiratory centers of the central nervous system. Short of death, repeated and prolonged exposure to carbon monoxide can alter sensory protection, temporal perception, and higher mental functions. Lipid-soluble aerosols can enter the body and be absorbed in the lipids of the central nervous system. Once there, their effects may persist long after the initial contact has been removed. Examples of agents of long-term chronic effects are organic phosphate pesticides and aerosols carrying the metals lead, mercury, and cadmium. 

F. S. Zhang, J. Ma, and Y. P, Cao, Phosphorus deficiency enhances root exudation of low-molecular weight organic acids and utilization of sparingly soluble inorganic phosphates by radish (Raphanus. sativus L.) and rape Bra.ssica napus L.) plants. 

Especially in dicotyledonous plant species such as tomato, chickpea, and white lupin (82,111), with a high cation/anion uptake ratio, PEPC-mediated biosynthesis of carboxylates may also be linked to excessive net uptake of cations due to inhibition of uptake and assimilation of nitrate under P-deficient conditions (Fig. 5) (17,111,115). Excess uptake of cations is balanced by enhanced net re-lea,se of protons (82,111,116), provided by increased bio.synthesis of organic acids via PEPC as a constituent of the intracellular pH-stat mechanism (117). In these plants, P deficiency-mediated proton extrusion leads to rhizosphere acidification, which can contribute to the. solubilization of acid soluble Ca phosphates in calcareous soils (Fig. 5) (34,118,119). In some species (e.g., chickpea, white lupin, oil-seed rape, buckwheat), the enhanced net release of protons is associated with increased exudation of carboxylates, whereas in tomato, carboxylate exudation was negligible despite intense proton extrusion (82,120). 

Total phosphorus includes colloidal inorganic phosphate, casein (organic) phosphate, soluble inorganic phosphate, ester phosphate and phospholipids. 

About one-tenth of the P in milk (i.e., about 100 mg/liter) is in the form of water-soluble organic esters of orthophosphoric acid. A list of such esters that have been detected in milk is presented in Table 1.8. Most of them are sugar phosphates and constituents of phospholipids. Reported concentrations of some of the compounds vary considerably, and complete quantitation of the group has not been made. 

The variability of the P content of fulvic acids appears to be a function of both the hydrologic conditions and the nutrient status of the aquatic system in which the fulvic acids were formed. McKnight et al. (1985) hypothesized that the P in Thoreau s Bog fulvic acids was in the form of organic phosphate esters or inositol phosphates, which are major phosphorus products from the breakdown of plant material. The solubility of these P-containing moieties would be greater in bogwater than in most surface... 

Wet process phosphoric acid made from calcined rock is preferred feed stock because it is devoid of the soluble organics and sludges present in acid made from sedimentary phosphates. However, calcination is expensive so that some plants are willing to go through laborious clarification to avoid it. 

Many such studies of sedimentary phosphorus profiles, also incorporating pore water measurement of soluble reactive phosphate, have demonstrated that redox-controlled dissolution of iron (hydr)oxides under reducing conditions at depth releases orthophosphate to solution. This then diffuses upwards (and downwards) from the pore water maximum to be re-adsorbed or co-precipitated with oxidized Fe in near-surface oxic sections. The downwards decrease in solid phase organic phosphorus indicates increasing release of phosphorus from deposited organic matter with depth, some of which will become associated with hydrous iron and other metal oxides, added to the pool of mobile phosphorus in pore water or contribute to soluble unreactive phosphorus . The characteristic reactions involving inorganic phosphorus in the sediments of Toolik Lake, Alaska, are shown in... 

The microbial cycling of phosphorus does not alter its oxidation state. Most phosphorus transformations mediated by microorganisms can be viewed as inorganic to organic phosphate transfers or as transfers of phosphate from insoluble, immobilized forms to soluble or mobile compounds. Various microorganisms have evolved transport systems for the regulated acquisition of phosphate from the environment. 

The essentials of the major pathway to Ins P6 in yeast nuclei can be summarized as follows Ins — Ptdlns, catalyzed by Ptdlns synthase Ptdlns —>PtdIns(4,5) P2, catalyzed sequentially by two specific kinases PtdIns(4,5)P2—>Ins (1,4,5)P3, catalyzed by a Ptdlns-specific phospholipase C Ins(l,4,5)P3—>—> Ins(l,3,4,5,6)P5, catalyzed by an Ins(l,4,5)P3 3-/6-kinase Ins(l,3,4,5,6)P5 —> Ins P6, catalyzed by an Ins(l,3,4,5,6)P5 2-kinase. This is now viewed as the canonical PLC-dependent pathway. Recent genetics studies have shown that this pathway is also critical to Ins P6 synthesis in Drosophila and rat cells (Fujii and York, 2004 Seeds et al., 2004). In contrast, the sole genetic evidence in any organism for a PLC-independent pathway like that described above in Dictyostelium and Spirodela, one that proceeds solely via soluble Ins phosphates, consists of one elegant study using Dictyostelium (Drayer et al., 1994). In this study the presence and levels of the whole series of Ins phosphates typical of a wild-type Dictyostelium, including Ins(l,4,5)P3 and Ins P6, where shown to be essentially identical in a PLC-null line. Thus some pathway to Ins(l,4,5)P3 and Ins P6 independent of PLC must exist in this organism. 

Samec and coworkers have differentiated between the fractions on the basis of phosphorus content. Undoubtedly, organic phosphate is associated primarily with the B-fraction of potato starch, contributing polarity to that component. In the case of corn starch, the distinction is not as sharp, since the total phosphorus content is very much lower. Also, it is possible to separate the B-fraction of corn starch into subfractions of high and low phosphorus content, and these do not differ materially in. solubility behavior or alkali lability. Thus phosphorus is believed to constitute only a minor difference between the fractions. 

Anderson, G. and Malcolm, R.E., 1974. The nature of alkali-soluble soil organic phosphates. J. Soil Sci., 25 282—297. 

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