Tissue phosphorus concentrations

Third, most of the available evidence suggests that, at a given soil P concentration, plants growing at elevated [CO2] are capable of maintaining their tissue phosphorus concentrations. This is in contrast to nitrogen and occurs because of the positive effects of larger root systems on the extent of root mycorrhizal colonization, root organic acid efflux per plant, and root acid phosphatase activity. All three processes play important roles in phosphorus acquisition. 

Fig. 10.3. The relationship between tissue phosphorus concentration and surface phosphatase activity for two mosses growing in Upper Teesdale, northern England. Data are from mosses sampled during an annual cycle and activity is expressed as p,mol para-nitrophenol (pNP) per g dry weight/h. Data taken from Turner etal. (2003a).

FIGURE 9.42 Mean plant tissue phosphorus concentration (percentage dry weight) of emergent wetland plants grown under conditions of sustained fertilization. (From McJannet et ah, 1995.)... 

The range of phosphorus concentration in live biomass and litter varies with wetland types (Figure 9.43). Phosphorus concentration ranged from 0.2 to 2.8 g kg for live biomass and from 0.1 to 1.7 g kg for litter. For live tissue, phosphorus concentration was in the order of bogs < rich fens < moderate-rich fens < swamps, whereas for litter, phosphorus concentrations were in the order of poor fens < rich fens < moderate-rich fens < marshes and swamps (Bedford et al., 1999). 

Periphyton is abundant in oligotrophic areas of the Everglades and is responsible for significant primary production and phosphorus storage. In these systems, periphyton productivity and tissue phosphorus concentration are strongly related to phosphorus concentration of the water column. 

Effects of Changes in Tissue Fluid Calcium and Phosphorus Concentration ON Bone Mineral and on Parathyroid Activity... 

Sodium phosphate P 32 is a radiopharmaceutical. Phosphorus is necessary to the metabolic and proliferative activity of cells. Radioactive phosphorus concentrates to a very high degree in rapidly proliferating tissue. Sodium phosphate P 32 decays by beta emission with a physical half-life of 14.3 days. The mean energy of the sodium phosphate P 32 beta particle is 695 keV. It is indicated in the treatment of polycythemia vera, chronic myelocytic leukemia, and chronic lymphocytic leukemia and skeletal metastases. 

The term d[P j,]/dt is calculated assuming that the concentration of phosphorus in all decomposing litter is 0.16 mmol 1110 . This is based on the 68% retranslocation of P from leaves and fine roots and the average branch, bole, and coarse root P concentrations (Sec. 3.2). Where the sensitivity of the model to P accumulation in the microbial carbon pool is tested, based on data summarized by Gijsman et al. (1996) we use a tissue P concentration for microbes of 6.4 mmol P moG C. In all simulations, it is assumed that soil phosphorus mineralization proceeds with a rate constant of 0.5 year , with phosphorus mineralization proceeding independently of carbon mineralization. This is on the basis of the evidence discussed in Sec. 2.1. Indeed, inflexible soil carbon pool C/P ratios which effectively link phosphorus mineralization rate to the carbon mineralization rate in models such as CENTURY (Parton et al, 1988) have been strongly criticized by some tropical soil chemists (Gijsman et al, 1996). 

Phosphate is present in plasma, extracellular fluid, cell membrane phospholipids, intracellular fluid, collagen, and bone. More than 80% of total body phosphate is found in bone and -15% in soft tissues. Phosphorus (P) in the body exists in both organic and inorganic forms. Organic forms include phospholipids and various organic esters. In extracellular fluid, the bulk of phosphorus exists as inorganic phosphate (Pj) in the form of NaH PO and NajHPO. The aggregate level of Pj modifies tissue concentrations of Ca + and plays a major role in renal acid excretion. Within bone, phosphate is complexed with calcium as hydroxyapatite and calcium phosphate. 

FIGURE 9.43 Relationship between phosphorus concentration of live tissue and litter (A, wetland plants of temperate northern wetlands [from Bedford et ah, 1999] B, Typha and Cladium from northern Everglades C, bogs and fens [from Kellog and Bridgham, 2003]). 

Plants contribute to soluble phosphorus not only after their death but also while they are still alive, as older tissues leach. Uptake of phosphorus by vegetation maintains low soluble phosphorus concentration in the soil profile. A large portion of phosphorus stored in belowground biomass is usually not accounted for in mass balance studies. Most of the emphasis is placed on aboveground... 

Note Y = mass N P ratio of the plant tissue X = soil total phosphorus concentration (mg kg ) ... 

Recently, the first applications of LA-ICP-MS for analysis of biological and clinical samples have been reported. In dental analysis, calcium, silver and mercury have been measured in low concentrations to identify nano-leakages of teeth restorations. A newly developed cryogenically cooled laser cell (cryocell) for ablation allows the determination of trace elements in frozen tissues, making time-consuming digestions unnecessary in many cases. In proteins separated by gel electrophoresis, selenium and phosphorus concentrations have been determined using standards for quantification separated under the same electrophoretic conditions. 

The application of biosolids also increases the nutritional value of blue grama. Tissue levels of nitrogen, phosphorus, potassium, and crude protein increased to recommended tissue concentrations with biosolids treatments. Trace metals in blue grama grass did not increase during the study, thereby eliminating concerns that toxic amounts of these elements could be transferred to grazing animals. 

A study with a dog exposed to an occluded dermal dose of TOCP labeled with radioactive phosphorus provides limited evidence that organophosphate esters in hydraulic fluids may be widely distributed after dermal absorption (Hodge and Sterner 1943). Similar widespread distribution of radioactivity among tissues was observed in male cats after dermal exposure to [uniformly labeled 14C-phenyl]TOCP (Nomeir and Abou-Donia 1986). Tissues and fluids with the highest concentrations of radioactivity in these studies included the bile, gall bladder, urinary bladder, liver, kidney, and fat, thus suggesting that TOCP and metabolites are somewhat preferentially distributed to these tissues. 

Twenty-four hours after application of 2.094 g TOCP labeled with radioactive phosphorus to a 15x20 cm area of clipped and depilated abdominal skin, radioactivity was detected in the following tissues in a dog, listed in order of decreasing concentration (counts per gram of tissue) skin and facia at site of application, liver, omental fat, blood, kidney, lung, muscle (triceps femoris), spinal cord, heart, spleen = brain = sciatic nerve, and bone (femur) (Hodge and Sterner 1943). 

It has also been demonstrated in animals that lead blocks the intestinal responses to vitamin D and its metabolites (Smith et al. 1981). Dietary concentrations of lead in combination with a low phosphorus or a low calcium diet administered to rats suppressed plasma levels of the vitamin D metabolite, 1,25-dihydroxycholecaliferol, while dietary intakes rich in calcium and phosphorus protected against this effect (Smith et al. 1981). Thus, animals fed a diet high in calcium or phosphorus appear to be less susceptible to the effects of lead, because of hindered tissue accumulation of lead. 

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