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Showing papers on "Phosphorus published in 1978"


Journal ArticleDOI
TL;DR: Using a ‘split root’ technique, it was found that phosphorus fertilization of half of the root system of sudangrass could significantly reduce the number of chlamydospores of the mycorrhizal fungus Glomus fasciculatus in the unfertilized half ofthe root system.
Abstract: SUMMARY Using a ‘split root’ technique, it was found that phosphorus fertilization of half of the root system of sudangrass could significantly reduce the number of chlamydospores of the mycorrhizal fungus Glomus fasciculatus in the unfertilized half of the root system. In a second experiment, vials of soil containing different concentrations of phosphorus were inserted into pots of sudangrass which were fertilized with different amounts of phosphorus and inoculated with G. fasciculatus. The numbers of chlamydospores, vesicles and arbuscles and the amount of hyphae produced by G. fasciculatus on roots within the vials were not influenced by the soil P in the vials but were inversely correlated with the concentration of P in roots outside the vial. All evidence indicates that it is the concentration of P within the plant and not the soil P which leads to a reduction in colonization, infection, and spore production of G. fasciculatus.

328 citations


Journal ArticleDOI
TL;DR: An isotopic shift of the (31)P nuclear magnetic resonance due to (18)O bonded to phosphorus of 0.0206 ppm has been observed in inorganic orthophosphate and adenine nucleotides, proving that bond cleavage occurs between the alpha P and the alpha-beta bridge oxygen.
Abstract: An isotopic shift of the 31P nuclear magnetic resonance due to 18O bonded to phosphorus of 0.0206 ppm has been observed in inorganic orthophosphate and adenine nucleotides. Thus, the separation between the resonances of 31P18O4 and 31P16O4 at 145.7 MHz is 12 Hz and, in a randomized sample containing ∼50% 18O, all five 16O-18O species are resolved and separated from each other by 3 Hz. Not only does this yield the 18O/16O ratio of the phosphate but, more important, the 18O-labeled phosphate in effect can serve as a double label in following phosphate reactions, for oxygen in all cases and for phosphorus, provided the oxygen does not exchange with solvent water. Thus, it becomes possible to follow labeled phosphorus or labeled oxygen continuously as reactions proceed. Rate studies involving (i) phosphorus and (ii) oxygen are illustrated by continuous monitoring of the exchange reactions between (i) the β phosphate of ADP and inorganic phosphate catalyzed by polynucleotide phosphorylase and (ii) inorganic orthophosphate and water catalyzed by yeast inorganic pyrophosphatase. In the ADP—Pi exchange, the Pi (18O4) yielded an α P(16O318O) and a β P(18O4), proving that bond cleavage occurs between the α P and the α-β bridge oxygen. Among the many additional potential uses of this labeling technique and its spectroscopic observation are: (i) different labeling of each phosphate group of ATP, (ii) to follow rate of transfer of 18O from a nonphosphate compound such as a carboxylic acid to a phosphate compound, and (iii) to follow the rate of scrambling (for example, of the β-γ bridge oxygen of ATP to nonbridge β P positions) and simultaneously the rate of exchange of the γ P nonbridge oxygens with solvent water in various ATPase reactions.

199 citations


Journal ArticleDOI
01 Sep 1978
TL;DR: In this paper, the authors conducted two experiments with filtered lake water and Lake Mendota mud in darkness and under aerobic conditions to determine if Chironomus riparius affected P release from lake sediment.
Abstract: To determine if Chironomus riparius affected P release from lake sediment, we conducted two experiments with filtered lake water and Lake Mendota mud in darkness and under aerobic conditions. Six d...

198 citations



Journal ArticleDOI
TL;DR: In this article, the stochastic properties of anoxic Long Island Sound sediments were examined through changes in the concentration of dissolved sulfate, ammonia, reactive phosphate, and other chemical species with depth in interstitial waters.
Abstract: The stoichiometry of nutrient regeneration in anoxic Long Island Sound sediments is examined through changes in the concentration of dissolved sulfate, ammonia, reactive phosphate, and other chemical species with depth in interstitial waters. In offshore sediments the mean AS04:ANH4:ACP ratio is -53:4.6:0.37; in shallow harbor sediment it is -53: 19:3.3 and ANI14:AZP ratios are half the offshore ratio. These indicated shoreward changes probably rcflcct more rapid deposition, and thus less preferential stripping of P and N from organic material before burial in shallow water harbor sediments, or selective stripping in the heavily bioturbated upper sediment layers offshore, or both. The effects of differential diffusion and adsorption of ammonia and phosphorus are considered. Phosphate concentration maxima in ammonia- and phosphate-rich shallow harbor sediments yield evidence for possible equilibrium with respect to vivianite, Fc3(P04)z*8Hz0, and struvitc, MgNI14P04+611z0. Martens and Berner (1977) reported on dissolved gases in the interstitial waters of nearshore Long Island Sound sediments. We here consider nutrient regeneration and phosphate removal in these same sediments, examine the stoichiometry of nutrient regeneration by using concentration vs. depth profiles of dissolved sulfate, ammonia, and reactive phosphate, and discuss possible authigenic phosphate mineral precipitation associated with high phosphate regcneration rates. We thank M. B. Goldhaber and J. Westrich for comments and discussion concerning this work. Remarks by J. Murray and S. Emerson led to significant improvements. A. Ruggiero provided analytical chemical assistance. M. Reed’s assistance with coring operations was indispensable.

177 citations


Journal ArticleDOI
TL;DR: The relationship between total phosphorus and phytoplankton biomass for a group of Ontario lakes is better defined if summer average cell volume is used instead of average chlorophyll a concentration.
Abstract: There is considerable variation in published phosphorus-chlorophyll relationships, some of which can be accounted for by variation in sampling and analytical techniques. As well, there can be significant inherent variability in a single phosphorus-chlorophyll relationship under even ideal sampling and analytical conditions. A survey of the literature shows that the cellular chlorophyll content of algae ranges over two orders of magnitude (0.1—9.7% of fresh weight). Average daily radiation intensity and nutrient availability (especially N) appear to be the major factors controlling chlorophyll content of algal cells. The relationship between total phosphorus and phytoplankton biomass for a group of Ontario lakes is better defined if summer average cell volume is used instead of average chlorophyll a concentration.

175 citations


Journal ArticleDOI
12 Jul 1978-Oikos
TL;DR: It is hypothesized that phosphorus released by microorganisms during their periodic population crashes accounts for most of the phosphorus return to the available phosphorus pool and that decomposition rate at Barrow is limited by the rate at which these microbial populations recover.
Abstract: The bulk of all phosphorus which circulates through the Barrow wet meadow tundra occurs in dead soil organic matter and has a residence time of 220 yr. In contrast, the soil solution phosphorus pool has a residence time of 10 h and must be replenished 200 times in the course of the growing season. Since atmospheric and weathering inputs of phosphorus to the Barrow tundra are negligible, decomposition of organic matter is the major avenue by which the soil solution phosphorus is replenished. Plant and animal biomass is largely belowground and is associated with the decomposition process or with extraction of phosphorus and other nutrients from soil. Forty percent of the annual transfer of phosphorus to the soil soluble P pool occurs within 10 d of snowmelt. Evidence is presented indicating that decomposition is the bottleneck in the Barrow phosphorus cycle. We hypothesize that phosphorus released by microorganisms during their periodic population crashes accounts for most of the phosphorus return to the available phosphorus pool and that decomposition rate at Barrow is limited by the rate at which these microbial populations recover. This rate of return to the available phosphorus pool in turn determines the rate of phosphorus uptake by vascular plants.

161 citations


Journal ArticleDOI
TL;DR: Correlation and regression analyses were used to assess several expressions for phosphorus loading, with and without corrections for water renewal and sedimentation, as predictors of total phosphorus concentration, chlorophyll, phytoplankton volume, and phy Topolankton production in the Experimental Lakes Area (ELA) lakes.
Abstract: Correlation and regression analyses were used to assess several expressions for phosphorus loading, with and without corrections for water renewal and sedimentation, as predictors of total phosphor...

159 citations



Journal ArticleDOI
TL;DR: In this paper, a photoluminescent (PL) analysis at liquid-helium temperature is reported to obtain boron and phosphorus concentration in silicon crystals by using a novel method.
Abstract: A novel method to obtain boron and phosphorus concentration in silicon crystals by photoluminescent (PL) analysis at liquid‐helium temperature is reported. The intensity ratio between intrinsic and extrinsic components in the PL spectra reflects the impurity concentration. The tentative calibration curves for boron and phosphorus for our method are obtained by comparison with the results of the resistivity measurement. The detection limit of this method is estimated to be as low as 1×1011 cm−3 for boron and 5×1011 cm−3 for phosphorus. The degree of compensation can be estimated also. The PL method makes it possible to determine nondestructively the concentration of small amount of impurities in a small region of a specimen.

143 citations



Journal ArticleDOI
TL;DR: A subclinical myopathy may set the stage for rhabdomyolysis if acute, severe hypophosphatemia is superimposed upon a pre-existing sub clinical myopathy, and changes in serum phosphorus and CPK activity resembled those observed in patients with subclinical alcoholic myopathy.
Abstract: Clinical observations suggest that overt rhabdomyolysis may occur if severe hypophosphatemia is superimposed upon a pre-existing subclinical myopathy. To examine this possibility, a subclinical muscle cell injury was induced in 23 dogs by feeding them a phosphorus- and calorie-deficient diet until they lost 30% of their original weight. To induce acute, severe hypophosphatemia in the animals after partial starvation, 17 of the dogs were given large quantities of the same phosphorus-deficient diet in conjunction with an oral carbohydrate supplement, which together provided 140 kcal/kg per day. After phosphorus and caloric deprivation, serum phosphorus and creatine phosphokinase (CPK) activity were normal. Total muscle phosphorus content fell from 28.0+/-1.3 to 26.1+/-2.5 mmol/dg fat-free dry solids. Sodium, chloride, and water contents rose. These changes resembled those observed in patients with subclinical alcoholic myopathy. When studied after 3 days of hyperalimentation, the animals not receiving phosphorus showed weakness, tremulousness, and in some cases, seizures. Serum phosphorus fell, the average lowest value was 0.8 mg/dl (P <0.001). CPK activity rose from 66+/-357 to 695+/-1,288 IU/liter (P <0.001). Muscle phosphorus content fell further to 21.1+/-7.7 mmol/dg fat-free dry solids (P <0.001). Muscle Na and Cl contents became higher (P <0.01). Sections of gracilis muscle showed frank rhabdomyolysis.6 of the 23 phosphorus- and calorie-deprived dogs were also given 140 kal/kg per day but in addition, each received 147 mmol of elemental phosphorus. These dogs consumed their diet avidly and displayed no symptoms. They did not become hypophosphatemic, their CPK remained normal, and derangements of cellular Na, Cl, and H(2)O were rapidly corrected. The gracilis muscle appeared normal histologically in these animals. These data suggest that a subclinical myopathy may set the stage for rhabdomyolysis if acute, severe hypophosphatemia is superimposed. Neither acute hypophosphatemia nor rhabdomyolysis occur if abundant phosphorus is provided during hyperalimentation.

Journal ArticleDOI
TL;DR: One isolate, identified as Pseudomonas putida, grew with AEP as its sole carbon, nitrogen, and phosphorus source and released nearly all of the organic phosphorus as orthophosphate and 72% of the AEP nitrogen as ammonium, the first demonstration of utilization of a phosphonoalkyl moiety as a sole carbon source.
Abstract: Bacteria able to use at least one of 13 ionic alkylphosphonates of O-alkyl or O,O-dialkyl alkylphosphonates as phosphorus sources were isolated from sewage and soil. Four of these isolates used 2-aminoethylphosphonic acid (AEP) as a sole carbon, nitrogen, and phosphorus source. None of the other phosphonates served as a carbon source for the organisms. One isolate, identified as Pseudomonas putida, grew with AEP as its sole carbon, nitrogen, and phosphorus source and released nearly all of the organic phosphorus as orthophosphate and 72% of the AEP nitrogen as ammonium. This is the first demonstration of utilization of a phosphonoalkyl moiety as a sole carbon source. Cell-free extracts of P. putida contained an inducible enzyme system that required pyruvate and pyridoxal phosphate to release orthophosphate from AEP; acetaldehyde was tentatively identified as a second product. Phosphite inhibited the enzyme system.

Journal ArticleDOI
TL;DR: In this paper, a corn seedling was grown in the greenhouse on a loamy sand amended with cadmium, Cadmium-spiked sewage sludge, and sludge sludge.
Abstract: Corn (Zea mays L.) ‘Pioneer-3932A’ was grown in the greenhouse on a loamy sand amended with cadmium, cadmium-spiked sewage sludge, and sewage sludge. Soil pH was adjusted to approximately 5.7, 6.7, and 7.8, and phosphorus was applied at 0, 200, and 400 µg/g soil. Soil treatments were applied 0, 8, and 16 weeks prior to planting, and the plants were grown for 5 weeks. Increasing the pH of the soil amended with inorganic cadmium (CdSO₄) decreased the Cd concentration of corn seedlings by approximately 67%. The Cd concentration was reduced approximately 47% for a similar increase in pH on soil amended with Cd-spiked sludge. The Cd concentration of corn seedlings was significantly reduced by the addition of P. Increasing incubation time decreased the availability of added inorganic Cd, but increased the availability of Cd applied with sewage sludge. Increasing the amount of Cd added to the soils increased the Cd concentration of the corn seedlings regardless of the form of Cd used. Cadmium concentrations in the corn seedlings were significantly correlated with DTPA-extractable soil Cd. Solubility measurements of Cd in the acidified soils showed undersaturation with respect to all known Cd minerals, whereas in soils above pH 7.25 the Cd solubility was limited by CdCO₃ at a CO₂ level of 0.003 atm or higher and showed the expected hundredfold decrease in solubility for each unit increase in pH. The minerals Cd₃(PO₄)₂ and Cd(OH)₂ are much too soluble to account for the precipitation of Cd in these soils.

Journal ArticleDOI
TL;DR: The internal, or 'biochemical', cycling of phosphorus is probably of major significance in the functioning of eucalypt forests on Australian soils characterized by a low phosphorus content.
Abstract: Total litter fall in mature Eucalyptus obliqua forest is typical for warm temperate forest, in the range 3.6-5.5 t ha-1 yr-1. Fifty per cent of the litter fall occurs in the summer months, and the seasonal rate of litter fall is dependent primarily on temperature. The concentration of nutrients in litter fall varies significantly throughout the year. Prior to litter fall, about 70% of the phosphorus is withdrawn from that portion of the biomass which is to fall as litter and the amount of phosphorus cycled in the litter is therefore very small. At the other extreme, calcium is immobilized in large quantities immediately prior to litter fall. The internal, or 'biochemical', cycling of phosphorus is probably of major significance in the functioning of eucalypt forests on Australian soils characterized by a low phosphorus content.

Journal ArticleDOI
01 Aug 1978-Ecology
TL;DR: It appears that Myriophyllum spicatum can meet its requirements for N by root uptake from the sediment as well as by absorption from the water itself through stem and leaf tissue, and data suggest that the limiting con?
Abstract: A series of laboratory culture experiments was designed to investigate uptake of phosphorus and nitrogen by roots and shoots of Myriophyllum spicatum in a number of lake water/ substrate and nutrient medium/substrate environments. The plants were compared with respect to biomass, physical dimensions, and total P and N in the plant tissues. It appears that Myriophyllum spicatum can meet its requirements for N by root uptake from the sediment as well as by absorption from the water itself through stem and leaf tissue. It was also seen that Myriophyllum can absorb considerable quantities of P from the sediment via the root system and transport it to the shoot regions of the plant. Growth data suggest that N was growth-limiting for sand-grown plants in nitrate-deficient media, even though tissue N was high. Growth was not decreased in low-phosphate media, suggesting that phosphate-limiting conditions were probably not attained in these experiments. A synergistic relationship between P and N was noted; P in the water clearly affected the ability of Myriophyllum plants to take up nitrate from the water. These data suggest that the limiting con? centration of nitrate for Myriophyllum might vary considerably, depending in part on the phosphate concentration.


Journal ArticleDOI
TL;DR: The present communication suggests the presence of one pathway for this reduction in the microsomal system that does not seem to have been reported previously, and the importance of Cr(VI) metabolism does not diminish by the fact that Cr(III) compounds, at sufficiently high concentrations, have been found to be mutagenic in the Salmonella system.
Abstract: [3-5]. The present communication suggests the presence of one pathway for this reduction in the microsomal system that does not seem to have been reported previously. The more exact nature and magnitude of this process in various tissues need to be studied further. The carcinogenicity of Cr(VI) compounds-particularly less water-soluble ones-has been documented [6]. Cr(VI) has also been reported to be mutagenic in bacterial systems [7, 8]. The biological effect of Cr(VI) thus certainly depends on where it is reducedwhether in extracellular spaces or in the cytoplasm or the nucleus of various organ cells. The importance of Cr(VI) metabolism does not diminish by the fact that Cr(III) compounds, at sufficiently high concentrations, have been found to be mutagenic in the Salmonella system (unpublished data). This work has been supported by ERDA grant E(04-3)-34-PA156 and carried out in the laboratory of Dr. B.N. Ames, University of California, Berkeley, whom I would like to thank for his support and advice.

Journal ArticleDOI
TL;DR: In this paper, a positive significant correlation coefficient was found between total P and phytate P in cooked beans and cotyledons, when the beans-to-water ratio was 1:4.
Abstract: Phytate phosphorus, calcium, magnesium, zinc and iron were determined in black gram (Phaseolus muizgo) seeds. Phytate phosphorus (P) represents 79%± 0.48 of the total P in black gram seeds. Fifty percent of phytate P had disappeared on the 10th day of germination with a simultaneous increase in the quantities of available inorganic P. After cooking for 45 min, whole seeds and cotyledons did not show any breakdown in the phytate P or losses of minerals after initial leaching, when the beans-to-water ratio was 1:4. A positive significant correlation coefficient was found between total P and phytate P in cooked beans and cotyledons. During germination a negative significant correlation coefficient was established between total P and phytate P.


Journal ArticleDOI
TL;DR: Red sea bream, Chrysophrys major, fed diets containing different levels of phosphorus for 76 days were analyzed and it was found that the decrease of the dietary phosphorus level resulted in the increase in the lipid contents of the muscle, liver, and vertebrae and in the decrease in the glycogen content of the liver.
Abstract: Red sea bream, Chrysophrys major, fed diets containing different levels of phosphorus for 76 days were analyzed to determine the chemical composition of the entire body, dorsal muscle, liver, and vertebrae. It was found that the decrease of the dietary phosphorus level resulted in the increase in the lipid contents of the muscle, liver, and vertebrae and in the decrease in the glycogen content of the liver and in the crude ash, calcium, and phosphorus content of the vertebrae. Little difference, however, was noted in the Ca/P ratio in the vertebrae among the various experimental groups.

Journal ArticleDOI
TL;DR: When channel catfish fingerlings were fed semipurified diets supplemented with monobasic sodium phosphate, their minimum requirement of dietary phosphorus for satisfactory growth and bone mineralization was approximately 0.45%.
Abstract: When channel catfish fingerlings were fed semipurified diets supplemented with monobasic sodium phosphate, their minimum requirement of dietary phosphorus for satisfactory growth and bone mineralization was approximately 0.45%. The addition of calcium (calcium carbonate) to a phosphorus-supplemented diet increased growth rate slightly but not significantly. Availability of phosphorus for channel catfish, as determined by net absorption from the digestive tract, was 90-94% for monosodium and monocalcium phosphate, 65% for dicalcium phosphate (feed-grade), 40% for fish meal, 50-54% for soybean meal, and 25-28% for cereal products.


Journal ArticleDOI
TL;DR: The results indicate that moderate diet-induced phosphorus depletion can depress myocardial performance, and with repletion of phosphorus, myocardIAL performance improves.
Abstract: The effects of phosphorus depletion on cardiac muscle function in six awake dogs were evaluated with surgically implanted transducers to serially measure ascending aortic root blood flow and high fidelity left ventricular pressure. After the animals recovered from surgery, phosphorus depletion was induced by feeding them a synthetic phosphorus-deficient diet plus aluminum carbonate gel for 35 days, followed by the same diet with phosphorus supplementation for 21 days. In addition to the cardiac studies, sequential measurements of phosphorus content in skeletal muscle and phosphorus in serum were obtained to ascertain the level of phosphorus depletion. Serum inorganic phosphorus concentration (mg/100 ml) decreased from 5.1 +/- 0.1 on day 0 to 0.9 +/- 0.1 on day 35 (P less than 0.01), and total muscle phosphorus (content mmul/100 g fat-free dry weight) decreased from 28.0 +/- on day 0 to 22.6 +/- 0.5 on day 35 (P less than 0.01). During the period of phosphorus depletion, there was no significant change in heart rate; however, stroke volume (milliliter) and peak blood flow velocity (centimeter per second) declined from 24 +/- 2 to 17 +/- 2 (P less than 0.01) and 121 +/- 12 to 98 +/- 7 (P less than 0.01), respectively. Maximum ascending aortic blood flow acceleration (centimeter per second square) and maximum left ventricular time rate of change of pressure (mm Hg per second) also decreased from 4,630 +/- 313 to 3,817 +/0 346 (P less than 0.01) and 2,582 +/- 347 to 2,120 +/- 297 (P less than 0.01) during phosphorus depletion. After repletion all values returned to control values. These results indicate that moderate diet-induced phosphorus depletion can depress myocardial performance. With repletion of phosphorus, myocardial performance improves.

Journal ArticleDOI
TL;DR: In this paper, the results of two rice soils of south-eastern Australia were flooded for 146 days to simulate part of a rice-upland crop rotation, and the effects of additional organic matter (rice straw) and the growing of rice plants were examined.
Abstract: Intact cores of two rice soils of south-eastern Australia were flooded for 146 days to simulate part of a rice-upland crop rotation. The phosphorus sorptivity, and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 210 days, before, during and after flooding. The effects of additional organic matter (rice straw) and the growing of rice plants were examined. In non-flooded soils phosphorus sorptivity was mainly influenced by clay content; there were no relationships between extractable iron and phosphorus sorbed. On flooding there were large increases in acetate and oxalate extractable iron and phosphorus sorptivity. Additional organic matter initially increased the rates of formation of extractable iron, and phosphorus sorptivity increased accordingly. However, with prolonged waterlogging, levels of oxalate iron and phosphorus sorptivity reached values dependent on the free iron oxide content of the soils. The growth of rice plants had no significant effects on phosphorus sorptivity or extractable iron at any time of sampling. During oxidation of previously flooded soils, levels of phosphorus sorptivity and oxalate iron decreased rapidly, but did not return to levels occurring before reduction. The results are consistent with domination of phosphorus sorption processes by ferrous hydrous oxides during the flooded (reduced) phase and by poorly crystalline ferric hydrous oxides during the post-flooding reoxidation phase. Agronomic implications of the results are mentioned.


Journal ArticleDOI
TL;DR: In this paper, an automated technique for reactive phosphorus, sensitive to < 0.5 mg P m−3, is described, where interference from AsO3−4-As and mercuric chloride is removed by thiosulphate in acid solution.

Journal ArticleDOI
TL;DR: In this paper, an experiment was conducted to study the release of 32P from white clover plant residues in the presence and absence of growing oats plants in both low and high phosphorus status soils.
Abstract: An experiment was conducted to study the release of 32P from white clover plant residues in the presence and absence of growing oats plants in both low and high phosphorus status soils. Net reutilization of phosphorus from the added plant material after 48 days was highest in the high phosphorus system in the presence of plants (29.3 %) and least in the low phosphorus system in the absence of plants (0.6%). Watering to field capacity daily, every 3 days, or every 6 days, had no significant effect on reutilization rates. Evidence from the soil inorganic phosphorus data suggests that the addition of plant material resulted in a significant immobilization of soil phosphorus only in the low phosphorus soil in the absence of plants. The significance of these findings is discussed in relation to the large number of incubation studies conducted to study phosphorus turnover rates in soil.

Journal ArticleDOI
TL;DR: In this paper, Trifolium subterraneum and Ornithopus compressus were grown in soil and solution culture at varying P concentrations and the efficiency of P utilization was determined using the following criteria: (1) The ability to produce top dry matter with a given amount of applied P, (2) Tops dry matter produced per unit of P taken up, (3) TOPS dry matter generated at a constant plant P level and (4) Phosphorus uptake per unit root weight.
Abstract: Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus were grown in soil and solution culture at varying P concentrations. Efficiency of P utilization was determined using the following criteria: (1) The ability to produce tops dry matter with a given amount of applied P, (2) Tops dry matter produced per unit of P taken up, (3) Tops dry matter produced at a constant plant P level and (4) Phosphorus uptake per unit root weight. The order of efficiency varied according to the crieteria used. Using the agronomic definition (1), Serradella was the most efficient species at 70 days.