Showing papers on "Phosphorus published in 1991"

A critical review on the role of mycorrhizal fungi in the uptake of phosphorus by plants

Abstract: The beneficial effects of mycorrhizae on plant growth have often been related to the increase in the uptake of immobile nutrients, especially phosphorus (P). In this review the mechanisms for the increase in the uptake of P by mycorrhizae and the sources of soil P for mycorrhizal and non-mycorrhizal plants are examined. Various mechanisms have been suggested for the increase in the uptake of P by mycorrhizal plants. These include: exploration of larger soil volume; faster movement of P into mycorrhizal hyphae; and solubilization of soil phosphorus. Exploration of larger soil volume by mycorrhizal plants is achieved by decreasing the distance that P ions must diffuse to plant roots and by increasing the surface area for absorption. Faster movement of P into mycorrhizal hyphae is achieved by increasing the affinity for P ions and by decreasing the threshold concentration required for absorption of P. Solubilization of soil P is achieved by the release of organic acids and phosphatase enzymes. Mycorrhizal plants have been shown to increase the uptake of poorly soluble P sources, such as iron and aluminium phosphate and rock phosphates. However, studies in which the soil P has been labelled with radioactive 32P indicated that both mycorrhizal and non-mycorrhizal plants utilized the similarly labelled P sources in soil.

Leaf lifespan as a determinant of leaf structure and function among 23 amazonian tree species.

Abstract: The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de Rio Negro, Venezuela. Moreover, leaf lifespan was highly correlated with a number of important leaf structural and functional characterisues. Stomatal conductance to water vapor (g) and both mass and area-based net photosynthesis decreased with increasing leaf lifespan (r2=0.74, 0.91 and 0.75, respectively). Specific leaf area (SLA) also decreased with increasing leaf lifespan (r2=0.78), while leaf toughness increased (r2=0.62). Correlations between leaf lifespan and leaf nitrogen and phosphorus concentrations were moderate on a weight basis and not significant on an area basis. On an absolute basis, changes in SLA, net photosynthesis and leaf chemistry were large as leaf lifespan varied from 1.5 to 12 months, but such changes were small as leaf lifespan increased from 1 to 5 years. Mass-based net photosynthesis (A/mass) was highly correlated with SLA (r2=0.90) and mass-based leaf nitrogen (N/mass) (r2=0.85), but area-based net photosynthesis (A/area) was not well correlated with any index of leaf structure or chemistry including N/area. Overall, these results indicate that species allocate resources towards a high photosynthetic assimilation rate for a brief time, or provide resistant physical structure that results in a lower rate of carbon assimilation over a longer time, but not both.

Nutrient supply, nutrient demand and plant response to mycorrhizal infection.

Abstract: summary One of the most dramatic effects of infection by vesicular-arbuscular mycorrhizal fungi on the physiology of the host plant is an increase in phosphorus absorption. When phosphorus is limiting, the maximum extent to which mycorrhizal infection can improve plant performance is thus predicted to be a function of the phosphorus deficit of the plant, the difference between phosphorus demand and phosphorus supply. Phosphorus demand is defined as the rate of phosphorus absorption that would result in optimum performance of the plant as measured by growth rate, reproduction or fitness. The phosphorus supply is defined as the actual rate of phosphorus absorption under the prevailing conditions. Variation among plant taxa in morphological, physiological or phenological traits which affect either phosphorus demand or phosphorus supply (and thus phosphorus deficit) is predicted to lead to variation in potential response to mycorrhizal infection. The actual response to mycorrhizal infection is predicted to be a function of the increase in phosphorus uptake due to mycorrhizal infection and the phosphorus utilization efficiency of the plant. Demonstrated variability in responsiveness to mycorrhizal infection among plant taxa suggests that mycorrhizal fungi may play an important role in determining the structure of plant communities. Mycorrhizal infection may alter the phosphorus deficit or phosphorus utilization efficiency independently from its direct effect on phosphorus uptake, making the prediction of response to mycorrhizal infection based on the traits of non-mycorrhizal plants quite difficult. For example, infection may at times increase the rate of phosphorus accumulation beyond that which can be currently utilized in growth, reducing the current phosphorus utilization efficiency. Such momentary ‘luxury consumption’ of phosphorus may, however, serve a storage function and be utilized subsequently, allowing mycorrhizal plants ultimately to outperform non-mycorrhizal plants.

Chemistry of Phosphorus Transformations in Soil

Abstract: Phosphorus (P) is essential for plants and animals because of its role in vital life processes, such as in photosynthesis in plants and energy transformations in all forms of life. It also has a significant role in sustaining and building up soil fertility, particularly under intensive systems of agriculture.

Chemical fluxes and mass balances in a marine fish cage farm. II Phosphorus

Abstract: Phosphorus fluxes were measured in a marine fish cage farm in the Gullmar Fjord, western Sweden. The measured fluxes included fish food, juveniles, harvest, fish loss (dead fish and escapers), sedimentation from the cages and benthic solute release (in situ). Two different types of mass balances were constructed. The flux method was based on seasonal input of fish food and juveniles, sedimentation and removal by harvest, fish loss and benthic fluxes Mass balances according to the flux method were constructed for each of 2 consecutive growing seasons The accumulat~on method was based on total input of phosphorus through fish food and juveniles, removal by harvest and fish loss, and net accumulation in the sedmen t over 7 growing seasons. Both types of mass balances gave similar results. Of the total phosphorus input to the farm, 17 to 19 % was recovered in harvest, fish loss constituted 1 to 4 %, and 78 to 82 % was lost to the environment. The environmental loss of phosphorus for each ton of fish produced was 22.4 kg (1985), 19.6 kg (1986) and 21.9 kg (1980 to 1986). Of the loss to the environment, 34 to 41 O/ O was in dissolved form and 59 to 66 % was accumulated in the sediment. O n a seasonal basis, the benthic flux transferred 4 to 8 % of the sedimented phosphorus back to the overlying water This constituted about 1 O/o of the total phosphorus content in the sediment derived from the fish farm.

Energy Status and Functioning of Phosphorus-Deficient Soybean Nodules

Abstract: Characterization of the effects of long-term P deficiency and of onset and recovery from P deficiency on bacteroid mass and number per unit nodule mass and energy status of soybean ( Glycine max L. Merr.) nodules was used to investigate the mechanisms by which P deficiency decreases symbiotic N 2 fixation. The continuous P deficiency treatment (0.05 millimolar P) significantly decreased the whole plant dry mass, P, and N by 62, 90, and 78%, respectively, relative to the P-sufficient control (1.0 millimolar) at 44 days after transplanting. Specific nitrogenase activity was decreased an average of 28% over a 16-day experimental period by P deficiency. Whole nodules of P-deficient controls contained 70 to 75% lower ATP concentrations than nodules of P-sufficient controls. Energy charge and ATP concentrations in the bacteroid fraction of nodules were not significantly affected by P treatment. However, ATP and total adenylate concentrations and energy charge in the plant cell fraction of nodules were significantly decreased 91, 62, and 50%, respectively, by the P deficiency treatment. Specific nitrogenase activity, energy charge, and ATP concentration in the plant cell fraction increased to the levels of nonstressed controls within 2, 2, and 4 days, respectively, after alleviation of external P limitation, whereas bacteroid mass per unit nodule mass and bacteroid N concentration did not increase to the level of nonstressed controls until 7 days after alleviation of external P limitation. All of these parameters except bacteroid mass per unit nodule mass decreased to the levels of the P-deficient controls by 11 days after onset of external P limitation. Concentration of ATP in the bacteroid fraction was not significantly affected by alteration in the external P supply. Energy charge in the bacteroid fraction from plants recovering from P deficiency was decreased to a small (10%) but significant extent (P

Anion‐exchange membrane, water, and sodium bicarbonate extractions as soil tests for phosphorus

Abstract: Three techniques were evaluated as soil P tests for western Canadian soils: anion‐exchange membrane (AEM), water, and bicarbonate extraction. The AEM, water, and bicarbonate‐extractable total P represented novel approaches to compare to the widely used bicarbonate‐extractable inorganic P (traditional Olsen) soil test. In a range of Saskatchewan soils, similar trends in predicted relative P availability were observed for AEM, water extraction, bicarbonate‐extractable total P, and bicarbonate‐extractable organic P. Correlations between soil test values revealed AEM and water‐extractable P to be most closely correlated, consistent with the similar manner of P removal in the two tests. Phosphorus availability, as predicted by the tests, was compared to actual P uptake by canola and wheat grown on 14 soils in a growth chamber experiment. P uptake by canola was highly correlated with AEM (r2 = 0.86–0.90), water (0.87 ‐0.94), and bicarbonate‐extractable total (0.91) and inorganic (0.92) P. Uptake of P b...

Fertility status of selected millet producing soils of West Africa with emphasis on phosphorus

Abstract: Millet (Pennisetum americanum) producing soils of West Africa were sampled at selected locations throughout the Sudano-Sahelian agroecological zone. The nutrient status of these soils was determined and related to P dynamics. Soils were neutral to acid in reaction, but few had any measurable amounts of exchangeable Al. Total P, Bray 1 extractable P, and P adsorption maxima were low which reflected their low levels of clay and organic matter. Phosphorus sorption characteristics were controlled by the poorly crystalline Al and Fe phases and the soil clay fraction. The poorly crystalline Al and Fe phases were highly correlated with the clay fraction. The P external requirement ranged from 11 to 40 mg P/kg soil. Given the low levels of total and labile P and the low fixation capacity of these soils, low to moderate levels of P amendments are necessary for sustained productivity

Influence of phosphorus and silicon on lipia class production by the marine diatom Chaetoceros gracilis grown in turbidostat cage cultures

Abstract: Production of intracellular and extracellular lipid classes by Chaetoceros gracilis was studied over a wide range of supply rates of inorganic phosphorus and silicon. The cage culture turbidostat, a continuous culture technique providing closely controlled nutrient concentrations and population densities, was used for growing the diatom. Nutrient, intracellular lipid and chlorophyll a analyses were performed over the whole range of nutrients used, but dissolved lipid production was measured only at the extremes of the ranges of nutrient concentrations. The production of triglycerides, a storage class of lipids, was triggered by nutrient stress with either phosphorus or silicon, as had earlier been demonstrated with nitrogen. The synthesis of phospholipids was reduced under phosphorus stress, while the synthesis of chlorophyll a was increased by silicon stress. The increase in chlorophyll a per cell under silicon stress brings into question the use of this pigment as a measure of biomass. Particulate lipid ye ld was highest in intermediate concentrations of both nutrients.

Thermotolerant phosphate solubilizing microorganisms and their interaction with mung bean

Abstract: Several phosphate solubilizing microorganisms (PSM) were tested for their efficiency at 35°, 40° and 45°C. There was a marked variation in their ability to solubilise tricalcium phosphate and the effect was more pronounced at 45°C. Two bacterial and one fungal strain were found to be thermotolerant as they solubilised a large amount of tricalcium phosphate at the three tested temperatures. These thermotolerant strains were identified as Bacillus subtilis (TT0), Bacillus circulans (TT8) and Aspergillus niger (TT10). Seed inoculation of mung bean showed a better establishment of temperature tolerant strains as revealed by the rhizosphere population. The inoculation improved nodulation, the available P2O5 content of the alluvial soil, root and shoot biomass, straw and grain yield and phosphorus and nitrogen uptake of the crop. Among the bacterial strains, the best effect on yield was obtained with B. subtilis. However, statistically it was equivalent to streptomycin resistant mutant (M-20) and Pseudomonas striata (27). A. niger was less effective than bacteria. Though superphosphate was found to be a better source of phosphate fertiliser, the use of rock phosphate (RP40), coupled with phosphate solubilising bacteria (PSB), gave results comparable to superphosphate (SP20) + PSB inoculants.

Litterfall and nutrient fluxes in two montane tropical rain forests, Colombia

Abstract: Litterfall was sampled during one year in two undisturbed Andean forests at altitudes of 2550 and 3370 m in the Colombian Cordillera Central. Total small litterfall at 2550 and 3370 m was 7.03 and 4.31 tha-'y-' respectively, of which 4.61 and 2.82 were leaves, 1.06 and 0.76 woody parts, 0.66 and 0.27 reproductive parts, 0.22 and 0.23 epiphytes, 0.47 and 0.23 unclassified. Clear differences were also found in nutrient concentrations, both bctween different litter fractions from one site and between equivalent litter fractions from different sites. Weighted mean concentrations for total small litterfall were (mgg-', at 2550 and 3370m respectively): 11.7 and 7.3 for nitrogen; 0.86 and 0.44 for phosphorus; 8.4 and 3.1 for potassium. Comparison of nutrient concentrationis in crown leaves and shed leaves indicated important reallocation of nitrogen (39% at both sites) and phosphorus (450% at 2550m, 65% at 3370m) before leaf shedding. The results for litterfall amounts, litter nutrient concentrations and reallocation of nutrients in the two forests are consistent with such data obtainied in other montane forests in the wet tropics.

Decomposition and nutrient dynamics of litter in long‐term optimum nutrition experiments

Abstract: The chemical composition of the falling litter was investigated over the different fertilization regimes The nitrogen concentration in the needle litter increased with dosage of nitrogen fertilizer Nitrogen concentration in needle litter was positively correlated to those of lignin, sulfur and calcium, but negatively to those of zinc, aluminum, and manganese Phosphorus concentrations were negatively correlated to those of lignin, manganese, zinc, calcium and magnesium Concentrations of sulfur were negatively correlated to concentrations of zinc, calcium, aluminum, magnesium and boron The decomposition patterns of Norway spruce needle litter were followed in an optimum nutrition field experiment Control plots and plots given high dosages of nitrogen and phosphorus fertilizer were used As decomposition proceeded soluble substances disappeared quickly and the concentration of soluble substances consequently decreased fast Lignin, being a recalcitrant compound, increased in concentration and the conce

Organic phosphorus compounds 941 preparation, physical and biological properties of amino-arylmethylphosphonic- and-phosphonous acids

Abstract: The preparation, physical and spectroscopic properties of amino-arylmethylphosphonic- and -phosphonous acids, the phosphorus analogues of phenylglycine, are described. It is shown that several of the compounds prepared exhibit antifungal activity at 200 ppm. Thus 1e, 1f, 1g and 1h showed activity against Erysiphe (barley), 2a against Puccinia (wheat) and 6a against Botrytis (apple). Of particular interest is the high gameticidal activity of 3a in the greenhouse.

Effects of dietary calcium and available phosphorus concentration on digesta pH and on the availability of calcium, iron, magnesium and zinc from the intestinal contents of meat chickens.

Abstract: 1. The effects of high calcium intakes on the pH and availability of calcium, iron, magnesium and zinc in the gastrointestinal tract (GIT) contents of meat chickens were studied in two experiments. 2. A high dietary concentration of calcium (25.3 vs 10.7 g/kg) increased the pH of crop and ileum contents, but did not influence the pH of the contents of other segments of the GIT. 3. The solubilities of minerals in GIT contents were reduced and the size of dissolved mineral complexes were increased as the digesta moved from the duodenum and jejunum to the ileum. 4. After feeding diets with calcium and available phosphorus concentrations (15.3 and 4.3 g vs 21.8 and 4.3 g vs 22.6 and 8.3 g/kg), centrifugation of GIT contents showed that most (70-92%) of the calcium, iron, magnesium and zinc was in an insoluble form. High calcium diets reduced the proportion of soluble zinc associated with small complexes, and high calcium and available phosphorus diets reduced the proportions of soluble magnesium and zinc associated with small complexes. 5. These findings explain the mechanism of the reduced availability of zinc and magnesium in high calcium and high available phosphorus diets.

The effect of pH on the release of phosphorus from Potomac estuary sediments: Implications for blue-green algal blooms

Abstract: The recurrence of a blue-green algal bloom ( Microcystis aeruginosa ) in the fresh-water tidal portion of the Potomac estuary in 1983 was related to the enhanced release of phosphorus from benthic sediments The release of phosphorus was measured from Potomac estuary sediment cores incubated with water at pH levels encompassing the range outside (pH 7–8) and inside (pH 9·5–10·5) the 1983 bloom area Phosphate release under aerobic conditions increased as a function of overlying water pH: between pH 8 and 9 the sediment-water phosphate flux was low; beginning with an overlying water pH of 9·5, the phosphate flux markedly increased The increased release of phosphate at high pH is probably a result of solubilization of iron and aluminium phosphate complexes Phosphorus release rates from the sediments at high pH (pH 9·5–10·5) are similar to the phosphorus source needed to account for the excess phosphorus measured in the bloom area and required to support the phytoplankton production

Fluxes of carbon and phosphorus between symbionts in willow ectomycorrhizas and their changes with time

Abstract: summary One way of viewing a mycorrhizal symbiosis is as a balance between the nutritional ‘benefits’ and carbon ‘costs’ to the phytobiont. Phosphorus acquisition efficiency (the amount of phosphorus taken up per unit of carbon allocated belowground) can be used as an indicator of this balance. In this study, phosphorus uptake and belowground carbon allocation were measured using ectomycorrhizal (M) (Thelephora terrestris (Ehrh.) Fr.) and non-mycorrhizal (NM) Salix viminalis L. cv. Bowles Hybrid. Following 50, 60, 85 or 98 d of growth in a gamma-irradiated soil/sand mixture containing 4 mg bicarbunate-extractable P kg−1, seven randomly-selected cuttings of each treatment were harvested and their P contents determined. Nine d prior to each harvest, the three median plants from the group of seven were pulse labelled with 14C to determine the relative allocation of C aboveground and belowground. Mycorrhizal colonization of willow caused a two-fold increase in growth owing to substantially higher P uptake. Phosphorus inflow rates were almost three times as high for M root systems as for NM root systems over the interval up to the first harvest (3.2 × 10 −12 and 1.2 × 1012 mol m−1 s–1, respectively). Over the interval from 50 to 98 d, inflows into M plants were 50% higher than into NM plants (1.4 × 1012 and 0.9 × 10−13 mol m−1 s−1 respectively). The M plants allocated about 25 times as much carbon belowground as the NM plants for both periods. The P acquisition efficiency was higher in M than in NM plants during the first interval (16% and 40% higher using two different calculation methods), whereas during the second interval it was higher in NM than in M plants (33% and 44% higher using the two different methods). Thus, ectomycorrhizas can be very effective in supplying P to their hosts even at an early stage of infection. Furthermore, it is suggested that a temporal separation exists in the maximal fluxes of P and C between the fungus and the host of the mycorrhizal association. The results are discussed in the context of the nutrient requirements and carbon economies of field-grown woody plants.

Quantifiying external and internal nitrogen and phosphorus pools, as well as nitrogen and phosphorus supplied through remineralization, in coastal marine plankton by means of a dilution technique

Abstract: A theoretical framework was developed for analyzing Landry & Hassett (1982; Mar. Biol. 67: 283-288) type dilution assays under more general conditions, where phytoplankton growth might also be nutrient-limited. The theory, which accounts for growth on available internal and external pools as well as on nutrients .supplied through remineralization by grazers, was applied to a series of field experiments performed in nutrient-impoverished waters in the Oslofjord, Southern Norway, in summer 1988. Analysis of the experimental results indicates that the phytoplankton had intracellular stores of P sufficient for several hours of growth in all experiments, while internal stores of N were undetectable in 4 out of 6 cases. Dissolved N pools appeared to be of greater importance to the algae as a nutrient reservoir than were hssolved P pools. Significant nutrient supplies from remineralization were identified on 3 out of 6 occasions, compensating for around half of the estimated grazing losses in each case. The supplies of remineralized N and P were closely balanced with respect to the growth demands of the phytoplankton, indicating that the surplus of cellular P originated from other sources.