Translocation Of Phosphorus Research Articles

Simulating the effects of biomanipulation on the food web of Lake Ringsjön

A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjon, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.

Vertical movements by planktonic cyanobacteria and the translocation of phosphorus: implications for lake restoration

1. Vertical movements of cyanobacteria during summer stratification were studied in Cauldshiels Loch, a small dimictic temperate lake. 2. Filaments of the three species of cyanobacteria dominant in the summer phytoplankton were recorded moving vertically in both directions, by simple traps deployed just below the thermocline. 3. These phytoplankters could potentially exploit opposing ends of the vertical light/nutrient gradient that existed in the water column during stratification. 4. The hypolimnion and water overlying the sediments were enriched by phosphorus released from the sediments. This internal loading to the lake provides a source of phosphorus available to migrating cyanobacteria to sustain production and growth in the epilimnion. 5. In this study, cyanobacteria filaments moving from the hypolimnion were found to be translocating phosphorus to the epilimnion. 6. Following reduction of external phosphorus loading, utilization of such internal phosphorus sources may delay expected reductions of bloom-forming cyanobacterial communities, and consequent improvements in other aspects of water quality. Copyright © 1999 John Wiley & Sons, Ltd.

Tolerância de genótipos de cafeeiro ao alumínio em solução nutritiva. II. Teores de P, Ca e Al e eficiência ao P e Ca

Foi instalado um experimento, em janeiro de 1994, em casa de vegetação do Departamento de Fitotecnia da Universidade Federal de Viçosa, Estado de Minas Gerais. Com o objetivo de avaliar o efeito do alumínio nos teores de P, Ca e Al e na eficiência ao fósforo e cálcio de nove genótipos de café, as plantas foram crescidas em solução nutritiva com 0 e 0,296 mmol L-1 de alumínio, com pH 4,0, por um período de 115 dias. Após esse período, as plantas foram divididas em folhas superiores, folhas inferiores, primeiro par de folhas totalmente expandido, caule e raízes, para a determinação da matéria seca e de concentrações de fósforo, cálcio e alumínio. A tolerância ao alumínio foi associada ao menor acúmulo de fósforo nas raízes, à menor redução na translocação desse nutriente para a parte aérea, à menor redução na absorção de cálcio e à maior eficiência no uso do fósforo e do cálcio. Foi observado grande acúmulo de alumínio nas raízes, bem como um transporte restrito do elemento para a parte aérea, para todos os genótipos de café.

Wood decay and phosphorus translocation by the cord‐forming basidiomycete Phanerochaete velutina: the significance of local nutrient supply

Mycelial cord systems of Phanerochaete velutina (DC.: Pers.) Parmasto grown from 4 cm3 inocula on a nutrient‐depleted non‐sterile soil in compartmentalized laboratory microcosms were baited after 13 d of growth with either fresh, non‐sterile 4 cm3 wood blocks or control Perspex® blocks of the same contact area. After 112 d, mature mycelial systems, which were in senescent phase, were subjected to disturbance by supplying a new fresh wood bait diametrically opposite the existing bait and, after 126 d, to nutrient regime amendment by application of NPK solution. At harvest (186 d) there was a significant (P0·001) linear relationship between extra‐resource mycelial biomass and total wood decay over the preceding 74 d. Nutrient amendment alone did not significantly (P>0·05) affect extra‐resource mycelial biomass production or wood decay rates in either disturbed or undisturbed cord systems. However, both mycelial biomass production and resource decay were significantly (P0·05) enhanced when nutrient amendment and disturbance treatments were applied concurrently. Bi‐directional phosphorus translocation to inocula and wood baits (determined non‐destructively) was assessed by labelling the NPK solution applied distal or proximal to the initially supplied bait with 32P. In both disturbed and undisturbed cord systems the rate of 32P uptake from a local supply was two orders of magnitude higher than from a distal supply. In disturbed cord systems uptake of 32P by inocula, which were midway between the two radiotracer supply points, was significantly (P0·05) higher when the supply point contained a newly supplied wood bait. Net translocation of 32P to newly supplied wood baits increased with time at the expense of translocation to inocula and existing wood baits. The switch in direction of net phosphorus translocation, the importance of localized nutrient scavenging and the partitioning of wood decay are discussed in relation to the ecological significance of mycelial cords.

Eficiência de absorção, translocação e utilização de fósforo por variedades de trigo

Com vistas em obter variedades de trigo mais eficientes na absorção e, ou, utilização de fósforo, é importante a investigação das causas da maior eficiência de certas variedades. Realizou-se um experimento em solução nutritiva, com quatro concentrações de fósforo (1,6; 4,8; 12,9 e 32,3 µmol L-1), comparando cultivares considerados eficientes (Toropi e IAC 5) e ineficientes (IAS 20 e CNT 8) quanto à absorção de fósforo, translocação e utilização do nutriente, matéria seca produzida e morfologia das raízes (comprimento, raio médio e área superficial). O cultivo foi realizado em outubro e novembro de 1993, em casa de vegetação da Faculdade de Agronomia da UFRGS (Porto Alegre-RS). As variedades não se diferenciaram quanto ao conteúdo de fósforo na planta. Não houve relação entre a absorção de fósforo e a morfologia das raízes. Os cultivares Toropi e IAC 5 mostraram-se mais eficientes na utilização de fósforo, bem como na translocação desse nutriente para a parte aérea.

Phosphorus uptake and active growth of Elodea canadensis Michx. and Elodea nuttallii (Planch.) St. John

Two related submerged freshwater macrophyte (Elodea nuttallii (Planch.) St. John and Elodea canadensis Michx.) were used in a combination of in- and outdoor experiments to compare growth rates and routes of phosphorus uptake, translocation and possible excretion. Elodea nuttalli had a higher growth rate than Elodea canadensis both in the field and under laboratory conditions. The uptake and translocation of phosphorus was studied using 32P in a partitioned container. Roots and leaves were supplied with 32P separately and simultaneously. Both macrophyte species were able to take up phosphorus both with leaves and roots. The uptake rate of 32P by roots was higher in Elodea nuttallii when tracer was supplied to the root compartment only. Leaf uptake was stimulated by the supply of phosphate to both compartments, and the uptake was faster and reached a higher level than when the tracer was injected to the leaf compartment only. The 32P uptake by either roots or leaves was translocated. Shoot-to-root translocation predominated over the reverse. There was no significant difference between both species in root uptake rates, but leaf uptake was significantly higher in Elodea canadensis. The two studied Elodea species do not have a strong preferential source of phosphorus.

Phosphorus uptake and active growth of Elodea canadensis Michx. and Elodea nuttallii (Planch.) St. John

Abstract Two related submerged freshwater macrophyte ( Elodea nuttallii (Planch.) St. John and Elodea canadensis Michx.) were used in a combination of in- and outdoor experiments to compare growth rates and routes of phosphorus uptake, translocation and possible excretion. Elodea nuttalli had a higher growth rate than Elodea canadensis both in the field and under laboratory conditions. The uptake and translocation of phosphorus was studied using 32 P in a partitioned container. Roots and leaves were supplied with 32 P separately and simultaneously Both macrophyte species were able to take up phosphorus both with leaves and roots. The uptake rate of 32 P by roots was higher in Elodea nunallii when tracer was supplied to the root compartment only. Leaf uptake was stimulated by the supply of phosphate to both compartments, and the uptake was faster and reached a higher level than when the tracer was injected to the leaf compartment only. The 32 P uptake by either roots or leaves was translocated. Shoot-to-root translocation predominated over the reverse. There was no significant difference between both species in root uptake rates, but leaf uptake was significantly higher in Elodea canadensis . The two studied Elodea species do not have a strong preferential source of phosphorus.

Absorption and Translocation of Calcium and Phosphorus Supplied to the Top and Root of Tomato Seedlings

Absorption and Translocation of Calcium and Phosphorus Supplied to the Top and Root of Tomato Seedlings

Phosphorus Uptake and Utilization Efficiency in Peanut1

Abstract Cultivars of a crop can differ genetically with respect to their uptake, translocation, accumulation, and use of phosphorus. The objective of this paper was to evaluate genetic variation for P uptake and utilization among peanut (Arachis hypogaea L.) genotypes. Several traits contribute to the total P efficiency of the genotype, including root length, rate of P uptake per unit root length, leaf and pod characters such as P accumulation, and dry matter/yield produced per unit P absorbed [i.e., P efficiency ratio (PER)]. Peanut genotypes with increased P uptake and higher PER were identified. Some genotypes sustained higher PER at both low and high soil P availabilities.

Influence of xylem vascular architecture on the translocation of phosphorus from nodal roots in a genotype of Trifolium repens during undisturbed growth.

Our objective was to establish whether the xylem vascular connections (architecture) of a genotype of Trifolium repens L. had implications for the intraplant allocation of recently assimilated phosphorus (P). One nodal root of each plan! was isolated and fed 32 P-labelled nutrient solution for 24 h. The fed root was either on the parent axis (11-12 nodes proximal CO the apex) or on a branch at the third or fourth node along the branch when counting from the junction with the parent stolon. Allocation patterns were obtained by dissecting plants and assaying each dissected component for 32 P. Under conditions of undisturbed growth in a controlled environment xylem architecture was found to have an important influence on the intraplant distribution of 32 P from nodal roots. Allocation patterns of 32 P were consistent with those predicted from knowledge of the xylem vascular architecture of the genotype and a predominantly acropetal direction of the transpiration stream. For instance, very little 32 P (< 1 % of exported 32 P from the fed root) was found in branches on the opposite side of the stolon to the fed root, and the strong acropetal direction of the transpiration stream resulted in little allocation of 32 P to leaves that had traces that arose from axial bundles at positions proximal to that of the fed root (the leaf subtending the fed root and the next distal leaf had low 32 P content), to all plant organs proximal to the fed root (< 6%) and to all other roots (<4%). The high allocation of 32 P to the branch arising at the same node as the fed root (64%) reflects the numerous links that the- fed root has to vascular bundles in the branch (3-6, of which two are axial bundles) against the single connection it has to the adjacent lower axial bundle in the parent stolon. Allocation of 32 P to the leaf and axillary bud at each node along the branch strongly favoured nodes on the adaxial side, a result consistent with the fact that the root connections are to the upper and lower axial bundles on the adaxial side of the branch. Allocation to a particular node along the branch was also influenced by its nodal position relative to the fed root and the sink strength of its tissues for the transpiration stream.

Dynamics of phosphorus translocation in intact ectomycorrhizal systems: non-destructive monitoring using a β-scanner

Phosphorus uptake and translocation through intact mycelial systems of Paxillus involutus and Suillus variegatus infecting Pinus contorta seedlings was monitored non-destructively using a beta-scanner. Mycorrhizal plants were grown in flat perspex chambers (20 x 6 cm(2)) and root growth was restricted to the upper portion of each chamber enabling mycelial translocation to be studied over distances of up to 15 cm. P-32 was supplied, either directly to distal parts of the extending mycelium, or to single, cut mycelial strands in feeding dishes. Two-dimensional patterns of activity were accumulated as scans with a lateral resolution of 5 mm and a longitudinal resolution of 3-4 mm. No distinct translocation front could be detected but patterns of accumulation of label in the mycorrhizal roots were not consistent with movement by simple diffusion. Activity in translocating hyphae became visible only after the activity in mycorrhizal root lips had been visible for a few days. In all cases there was a lag period of 20-50 hours before P-32 could be detected in mycorrhizal root tips. Pre-feeding with unlabelled phosphate had no effect on this lag period. This implies continuous translocation of phosphate at low concentrations and a lag period due to the time needed for detectable levels of phosphate to accumulate in mycorrhizal roots. Thus the minimum velocity of phosphate movement in the hyphae would be 7.5 mm/h, if the first molecules of P-32 arriving at the roots could be detected and the transport distance is 15 cm. Accumulation of phosphate to the roots was fairly constant, but not linear. The phosphorus uptake rate by intact mycelial margins was nearly four orders of magnitude higher than the uptake rate of cut mycorrhizal strands. The results indicate that the fine, foraging hyphae are better suited for nutrient uptake than mycelial strands and that phosphorus translocation in the hyphae occurs by active translocation of small amounts rather than by mass flow. (Less)

Dynamics of phosphorus translocation in intact ectomycorrhizal systems: non-destructive monitoring using a β-scanner

Phosphorus uptake and translocation through intact mycelial systems of Paxillus involutus and Suillus variegatus infecting Pinus contorta seedlings was monitored non-destructively using a β-scanner. Mycorrhizal plants were grown in flat perspex chambers (20 × 6 cm 2) and root growth was restricted to the upper portion of each chamber enabling mycelial translocation to be studied over distances of up to 15 cm. 32P was supplied, either directly to distal parts of the extending mycelium, or to single, cut mycelial strands in feeding dishes. Two-dimensional patterns of activity were accumulated as scans with a lateral resolution of 5 mm and a longitudinal resolution of 3–4 mm. No distinct translocation front could be detected but patterns of accumulation of label in the mycorrhizal roots were not consistent with movement by simple diffusion. Activity in translocating hyphae became visible only after the activity in mycorrhizal root tips had been visible for a few days. In all cases there was a lag period of 20–50 hours before 32P could be detected in mycorrhizal root tips. Pre-feeding with unlabelled phosphate had no effect on this lag period. This implies continuous translocation of phosphate at low concentrations and a lag period due to the time needed for detectable levels of phosphate to accumulate in mycorrhizal roots. Thus the minimum velocity of phosphate movement in the hyphae would be 7.5 mm/h, if the first molecules of 32P arriving at the roots could be detected and the transport distance is 15 cm. Accumulation of phosphate to the roots was fairly constant, but not linear. The phosphorus uptake rate by intact mycelial margins was nearly four orders of magnitude higher than the uptake rate of cut mycorrhizal strands. The results indicate that the fine, foraging hyphae are better suited for nutrient uptake than mycelial strands and that phosphorus translocation in the hyphae occurs by active translocation of small amounts rather than by mass flow.

Phosphorus translocation by saprotrophic basidiomycete mycelial cord systems on the floor of a mixed deciduous woodland

Translocation of 32 P was examined in seven mycelial cord systems of Hypholoma fasciculare, Phanerochaete velutina and Phallus impudicus which had developed from wood block inocula placed on the floor of a mixed deciduous woodland. Five days after addition of radiotracer to the central inoculum activity was detected at the margins of cord systems, demonstrating translocation 32 P over distances up to 75 cm. Destructive sampling showed that radioactivity was present in cords and a range of wood and leaf litter components colonized by cord systems. Radioactivity was also detected in live Fragaria vesca plants and shoots of the moss Hypnum cupressiforme .

Translocation of soil-derived phosphorus in mycelial cord systems in relation to inoculum resource size

Uptake of 32P phosphorus from soil was investigated in mycelial cord systems of Phanerochaete velutina, Hypholoma fasciculare, Tricholomopsis platyphylla and Phallus impudicus which extended from 0.5, 2, 4 or 8 cm 3 beech ( Fagus sylvatica) inocula. Cord systems accumulated between 4.8 and 18.7% of phosphorus supplied to soil, according to species and size of inoculum. Phosphorus translocation to newly-colonized 2 cm 3 beech baits, determined non-destructively, was characterized by an initial steady phase, of 2.5 to 32 nmol P day −1 which lasted at least 12 days for all four species. After the initial steady phase, translocation rates declined. Initial mycelial extension and wood decay rates also varied with species and inoculum size. There was no clear relationship between phosphorus translocation rates, wood decay or the distribution of soil-derived phosphorus in cord system components. However, with increasing inoculum size, P. velutina systems allocated a significantly greater proportion of available phosphorus to newly-colonized baits. The degree to which distribution of soil-derived phosphorus in cord systems is related to nutrient conservation or metabolic demand in the fungi is discussed.

Translocation of soil-derived phosphorus in mycelial cord systems in relation to inoculum resource size

Abstract Uptake of 32 P phosphorus from soil was investigated in mycelial cord systems of Phanerochaete velutina, Hypholoma fasciculare, Tricholomopsis platyphylla and Phallus impudicus which extended from 0.5, 2, 4 or 8 cm 3 beech ( Fagus sylvatica ) inocula. Cord systems accumulated between 4.8 and 18.7% of phosphorus supplied to soil, according to species and size of inoculum. Phosphorus translocation to newly-colonized 2 cm 3 beech baits, determined non-destructively, was characterized by an initial steady phase, of 2.5 to 32 nmol P day −1 which lasted at least 12 days for all four species. After the initial steady phase, translocation rates declined. Initial mycelial extension and wood decay rates also varied with species and inoculum size. There was no clear relationship between phosphorus translocation rates, wood decay or the distribution of soil-derived phosphorus in cord system components. However, with increasing inoculum size, P. velutina systems allocated a significantly greater proportion of available phosphorus to newly-colonized baits. The degree to which distribution of soil-derived phosphorus in cord systems is related to nutrient conservation or metabolic demand in the fungi is discussed.

Effect of temperature on wood decay and translocation of soil-derived phosphorus in mycelial cord systems.

Uptake of 32 P phosphorus from soil was investigated at 5-25 °C in mycelial cord systems of Phanerochaete velutina (D.C.: Pers.), Hypholoma fasciculare (Huds.: Fr.) Kummer and Phallus impudiciis (L.) Pers. which extended from 2cm3 beech (Fagus sylvatica) inocula, and which had initially developed at either 10 or 25 °C. Uptake of phosphorus from soil was opportunistic, being unaffected by the presence of additional wood resource units in mycelial cord systems. The magnitude of phosphorus uptake was dependent on species, temperature during uptake and the temperature at which cord systems developed. Phosphorus translocation to newly colonized baits, determined non-destructively, was characterized by an initial rapid flux to a plateau in all three species. Initial rates of phosphorus translocation (up to 18·46 nmol P d-1 ) generally increased with temperature whilst total translocation was species and temperature dependent. There was evidence that both P. velutina and H. fasciculare displayed temperature acclimation, since phosphorus uptake and translocation at lower temperatures was greater in cord systems which had developed initially at 10° compared with 25 °C. Mycelial extension and wood decay rates also varied with species, initial development temperature and subsequent incubation temperature, but did not correlate with the temperature profiles of phosphorus uptake and translocation. Results are discussed in relation to nutrient acquisition, conservation and cycling in basidiomycete mycelial cord systems.

Phosphorus Accumulation and Translocation in Wheat as Affected by Cultivar and Nitrogen Fertilization

AbstractTo improve nutrient management strategies in wheat more information is needed about the interaction effects among nutrients in their uptake and redistribution in the plants, in relation to different genotypes. Therefore, two bread (T. aestivum L.) and two durum (T. durum Desf.) winter wheat cultivars were grown in the field for 2 years (1986, 1987) in a silty‐clay soil under different nitrogen (N) levels, in Northern Greece. Nitrogen at a rate of 150 kg ha−1 was applied before planting or 100 kg ha−1 before planting and then 50 kg ha−1 at early boot stage. Cultivar differences in phosphorus (p) concentration were observed only in vegetative parts but not in the grain. Maximum p accumulation was observed either at anthesis or at maturity. During grain filling dry matter and p accumulation in the grain followed almost the same pattern. Phosphorus translocation efficiency of the cultivars at the 2 years ranged from 70.7 to 84.3 % and the amount of p in the grain derived from translocation 52 to 100 %. Phosphorus translocation efficiency was weakly correlated with p content in grain only in 1986, while phosphorus harvest index (PHI) was positively correlated with harvest indst (HI) both years (r = 0.82** in 1986 and 0.75** in 1987). Nitrogen application mainly affected p accumulation of the cultivars via its effect on biomass production. The split N application promoted slightly the p uptake in 1987 and this resulted in the reduction of both the contribution of the translocated p to the grain and the efficiency of p utilization for total biomass. Results indicated that p accumulation and translocation and the efficiency of p utilization in wheat were mainly determined by the genotype in relation to environmental condition of growth.

Translocation of phosphorus from nodal roots in two contrasting genotypes of white clover (Trifolium repens)

Patterns of translocation of recently‐assimilated phosphorus (P) exported from‘young’ source roots (located 3–4 nodes from the stolon apex) and ‘old’ source roots (located near the base of the stolon) on the primary stolon of clonal plants of the forage legume white clover (Trifolium repens L.) were determined using 32P. Plants of a small‐leaved genotype and of a large‐leaved genotype were grown in sand culture at two notionally limiting or near‐limiting rates of P supply and one non‐limiting rate of supply. The small‐leaved genotype showed little response in growth rate to the full range of P treatments whereas growth of the large‐leaved genotype at the non‐limiting rate of P supply was 2. 4 times greater than at the two low rates of P supply. Source roots of both genotypes exported only 26–30% of the P they acquired to the shoot within 24 h when P supply was limited whereas at the high‐P rate 54% of recently‐assimilated P was exported. Patterns of translocation of exported P to specific sinks differed little between the genotypes and the P treatments; branches were the main sink, accounting for nearly 80% of the estimated amounts of P (μg day−1) exported from young and old roots combined. Translocation patterns from individual roots were determined largely by the modular structure of plants and by the location of the root relative to the major sinks, and were therefore consistent with the same source‐sink principles which govern carbohydrate translocation in clonally‐growing species. There were strong suggestions that storage of P in stolons and roots played a much greater role in the growth of the small‐leaved plants than of the large‐leaved plants.

Translocation of phosphorus from nodal roots in two contrasting genotypes of white clover (Trifolium repens)

Translocation of phosphorus from nodal roots in two contrasting genotypes of white clover (Trifolium repens)

EFEITOS DO FÓSFORO E DO ZINCO NO ARROZ DE SEQUEIRO EM LATOSSOLO VERMELHO ESCURO

Foi conduzido um experimento em casa de vegetação do Departamento de Fitotecnia, na Universidade Federal de Santa Maria, com o objetivo de estudar os efeitos de combinações de doses de fósforo e zinco sobre a produção de massa seca e acumulação de fósforo e zinco na planta do arroz de sequeiro. Utilizou-se vaso de plástico contendo 3,0kg de solo, Latossolo Vermelho Escuro sob vegetação de Cerrado, proveniente de Chapadão do Sul-MS, com teores iniciais de 2,1ppm de P e 0,50ppm Zn (extratores Mehlich e HCI 0,1 N, respectivamente). Adotou-se o delineamento blocos ao acaso com quatro repetições. Os tratamentos constituíram um fatorial 4x4 pela combinação de quatro doses de fósforo (zero, 60, 120 e 180kg/ha de P2O5), tendo como fonte o superfosfato triplo, e quatro doses de zinco (zero, 2,5; 5,0 e 10,0kg/ha de Zn), tendo como fonte o sulfato de zinco, aplicados no solo. Os resultados evidenciaram que a produção de massa seca da planta aumentou com a aplicação de doses mais elevadas de P e Zn. A aplicação de fósforo no solo aumentou sua acumulação e a acumulação de zinco na planta e reduziu o teor de zinco na planta e no solo. A aplicação de zinco no solo aumentou sua acumulação e reduziu o teor e acumulação de fósforo na planta. A translocação do fósforo e do zinco não foram afetadas pêlos tratamentos.