Forms of Organic Phosphorus

Phosphate also plays a central role in the transmission and control of chemical energy within the cells primarily via the hydrolysis of the terminal phosphate ester bond of the adenosine triphosphate (ATP) molecule (Fig. 3b). In addition, phosphate is a necessary constituent of phospholipids, which are important components in cell membranes and as mentioned before, of apatite, which forms structural body parts such as teeth and bones. It is not surprising, therefore, that the cycling of P is closely linked with biological processes. This connection is, in fact, inseparable as organisms cannot exist without P, and their existence controls, to a large extent, the natural distribution of P. 

Organic P also occurs in dissolved forms, particularly in euphoric surface waters, where it may exceed inorganic phosphate concentrations (Smith et al., 1986). The labile fraction of dissolved organic phosphorus may be the most rapidly cycled marine phosphate pool (Orrett and Karl, 1987 Jackson and Williams, 1985). This pool may also provide a buffer , providing utilizable phosphate to phytoplankton between episodic inputs from other sources (Jackson and Williams, 1985). 

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Hannapel, R.J., Fuller, W.H., Bosma, S. and Bullock, j.S. (1954a) Phosphorus movement in a calcareous soil. I. Predominance of organic forms of phosphorus in phosphorus movement. Soil Science 97, 350-357. 

The incorporation of phosphorus by green plants is the main means of entry of this element into the biosphere. If we consider a plant, the surroundings in which the roots live are very complex. Phosphorus is present in the form of sparingly, soluble calcium, iron and aluminium salts, as adsorbed anions on the soil particles and as organic compounds derived from the corpses of plants, animals and micro-organisms (iron, calcium or aluminium salts of phytin, and of nucleoproteins). In neutral or calcareous soils, the calcium salts of organic forms of phosphorus are more soluble... 

Phosphorus is an important component of feed, as it is crucial for bone and skeleton formation. About 70 % of phosphorus in vegetable feed ingredients is present in the form of phytate, an inositol-bound organic form of phosphorus that has a low bioavailability in monogastric animals. For this reason, the diet for monogastric animals like pigs and chickens is supplemented... 

M. A. Adams and J. S. Pate, Availability of organic and inorganic forms of phosphorus to lupins (Lupinus spp.). Plant Soil 745 107 (1992). 

Organic derivatives of phosphorus excel by the strong tendency of trivalent phosphorus to combine with oxygen or sulfur to form phosphine oxides and phosphates or their sulfur analogs. 

Bray, R.H. and Kurtz. (1945) Determination of total, organic and available form of phosphorus in soils. Soil Science 59, 39 5. 

Phosphorus is an essential nutrient for all cells. For organisms that absorb their mineral nutrients directly from the external medium, ionic inorganic phosphate (Pi, usually H2P04 or HP042 ) is the preferentially absorbed form of phosphorus. A macronutrient based on its contribution to biomass, Pi is one of the least available mineral nutrients in many environments. For example, the level of Pi in the solution phase of soils is often below those of many micronutrients (Fried Brosehart, 1967 Epstein, 1972). In soils, all major nutrient ions except Pi are normally present at concentrations from 1.0 to 0.1 mM whereas the Pi concentration is commonly 1.0 pM or less. In many natural ecosystems, phosphorus... 

Organic forms of carbon, nitrogen, sulfur, and phosphorus (typically less than 0.7 pm in diameter) contribute to bulk DOM. Humic substances,... 

III. ORGANIC FORMS OF LIMITING ELEMENT (LABILE DISSOLVED ORGANIC NITROGEN AND DISSOLVED ORGANIC PHOSPHORUS)... 

Sample dissolution and analyte conversion to a more easily detected species, e.g., the sequential injection determination of total nitrogen in wastewaters involving Kjeldahl oxidation and nitrate formation [141]. The spectrophotometric flow injection determination of organic phosphorus in natural waters [142], relying on the release of the different forms of phosphorus as orthophosphate, is another good example. 

There are several allotropic forms of phosphorus, but only white phosphorus and red phosphorus (see Figure 8.18) are of importance. White phosphorus consists of discrete tetrahedral P4 molecules (Figure 21.9). A solid (m.p. 44.2°C), white phosphorus is insoluble in water but quite soluble in carbon disulfide (CS2) and in organic solvents such as chloroform (CHCI3). White phosphorus is a highly toxic substance. It bursts into flames spontaneously when exposed to air hence it is used in incendiary bombs and grenades ... 

The various main forms of phosphorus show considerable difference in chemical reactivity the white is by far the most reactive form, and the black the least. White P is stored under water to protect it from the air, whereas the red and black are stable in air indeed, black P can be ignited only with difficulty. White P inflames in air and is soluble in organic solvents such as CS2 and benzene. Some reactions of both red and white P are shown in Fig. 13-2. 

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