Showing papers on "Phosphorus published in 1980"

The role of phosphorus in agriculture.

Abstract: The Role of phosphorus in agriculture , The Role of phosphorus in agriculture , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Phosphorus sources for aquatic weeds: water or sediments?

Abstract: Nine common species of aquatic macrophytes took all their phosphorus from the sediments when grown in situ in both a mesotrophic and a mildly eutrophic bay. Even under hypertrophic conditions, the sediments contributed an average of 72 percent of all the phosphorus taken up during growth. These experiments unambiguously demonstrate for the first time that submergent macrophytes in nature over-whelmingly depend on the sediments for their phosphorus supply and characterize them as potential nutrient pumps to the open water.

Mobilization of sediment phosphorus by submersed freshwater macrophytes

Abstract: SUMMARY. The mobilization of sediment phosphorus (P) by three submersed freshwater macrophyte species was investigated on five different sediments. The study was conducted under controlled environmental conditions in lucite columns that enabled the separation of sediment and plant roots from the overlying P-free ‘complete’ nutrient solution. The species investigated (Egeria densa, Hydrilla verticillata, and Myriophyllum spicatum) had minor root systems (on a biomass basis), but were demonstrated to be fully capable of deriving their P nutrition exclusively from the sediments. Phosphorus absorption and translocation into shoots (i.e., mobilization) was substantial, and in some cases suggested a greater than 1000-fold turnover of interstitial water PO4-P over a 3-month period. Sediment P mobilization, a function of both plant growth and tissue P concentration, differed considerably among plant species and sediments. Phosphorus release from the species investigated appears to be primarily dependent upon tissue decay rather than excretory processes. The mobilization of sediment P by submersed macrophytes represents an important aspect of the P cycle, and may affect the overall metabolism of lacustrine systems.

Soil phosphorus characterisation by 31p nuclear magnetic resonance

Abstract: Five New Zealand topsoils, including three sampled under introduced pasture and two in native tussock grasslands, were extracted with 0.5 M NaOH, and the different classes of phosphorus compounds i...

The development of waterlogging damage in wheat seedlings (Triticum aestivum L.)

Abstract: Decreases in the concentrations of nitrogen, phosphorus, potassium, calcium and magnesium, in the shoots of wheat seedlings soon after the start of waterlogging were mainly attributed to an inhibition of ion uptake and transport by roots in the oxygen deficient soil. There was a small net accumulation of nitrogen, phosphorus and potassium by the aerial tissues, principally the tillers rather than the main shoot. By contrast, calcium and magnesium accumulated in both tillers and main shoot. With waterlogging, nitrogen, phosphorus and potassium were translocated from the older leaves to the younger growing leaves, and in the case of nitrogen this was associated with the onset of premature senescence. Calcium and magnesium were not translocated from the older leaves, the younger leaves acquiring these cations from the waterlogged soil. The promotion of leaf senescence by waterlogging was counteracted by applications of nitrate or ammonium to the soil surface, or by spraying the shoots with solutions of urea, but the beneficial effects on shoot growth were small.

Translocation and transfer of nutrients in vesicular-arbuscular mycorrhizas. III. Polyphosphate granules and phosphorus translocation

Abstract: Summary X-ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm-3) of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high-voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra-matrical mycelium in soil measured in the light microscope were around 12·6 cm h-1. From these data a flux rate of about 2·7 × 10-8 mol P cm-2 s-1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.

Nitrogen Nutrition and Salinity Tolerance of Distichlis Spicata and Spartina Alterniflora

Abstract: In a greenhouse investigation Distichlis spicata (L.) and Spartina alterniflora (Loisel.) were grown from seed on freshwater, brackish, and marine sediments. These species were also concurrently grown in sand culture under conditions of nitrogen or phosphorus limitation in order to establish critical tissue concentrations of these elements. These experimentally determined values were used to assess the limiting nutrient status of the plants grown on the sediments. Growth of both species was nitrogen limited on most sediments, and phosphorus was consumed luxuriously on all sediments. Aboveground biomass was correlated with interstitial water nitrogen concentration of the sediments. Under low nutrient conditions relatively more biomass was allocated to belowground rather than aboveground portions of the plants. Although the availability of nitrogen ultimately determined biomass accrual, growth rate was affected by the sediment salinity. Analysis of plant tissues and the sediment interstitial water at the end of the investigation revealed selective uptake of potassium and exclusion of sodium. These processes increased the ratio of sodium to potassium in the interstitial waters and also resulted in increased sediment salinities. The effect of salinity stress on plant growth in Spartina marshes is discussed in relation to nitrogen limitation.

Acid phosphatase activity of intact roots and phosphorus nutrition in plants. 1. Assay conditions and phosphatase activity

Abstract: This veries sets out to investigate the possibility of developing root phosphatase activity as an indicator of plant efficiency in obtaining phosphorus from low phosphorus situations. This paper examines the effect of substrate pH, temperature, reaction time, microbial contamination and phosphorus nutrition on the expression of phosphatase activity of plant roots. Rye, wheat, buckwheat and subterranean clover plants have been used. Phosphatase (E.C. 3.1.3.4.1) activity measured by p-nitrophenyl phosphate (PNPP) assay was essentially the activity of the plant root. Increased acidity in the substrate, on its own, did not hydrolyse PNPP nor did microbial contamination significantly affect the plant value. Temperature and reaction time were positively related to the assay value, least variation in assay values occurring with substrate temperatures of 20¦C and reaction times of 60-120 min. Optimum pH for phosphatase activity lay in the range pH 5-6. Deficient plants had greater activities than sufficient ones. There was no evidence of alkaline phosphatase activity with phosphorus deficiency. In wheat, the phosphatase activity increased within the first 4 days of plants being deprived of phosphorus and reached its peak in 8 days. Some of the phosphatase was soluble, but most was associated with the root itself. There was evidence that it could be strongly adsorbed on cellulose nitrate filters.

Nitrogen and phosphorus distribution and utilization by Spartina alterniflora in a Louisiana gulf coast marsh

Abstract: Nitrogen and phosphorus content ofSpartina alterniflora Loisel and soil nitrogen were measured along a transect perpendicular to a stream in a Louisiana salt marsh in order to provide information on differences between the so-called streamside and inland regions. Total plant nitrogen and phosphorus levels in June and September tended to be greater at streamside than inland sites. Total soil nitrogen on a dry soil weight basis increased with distance inland from a natural stream toward an interdistributary basin in the marsh. Soil extractable ammonium-nitrogen levels measured in June were very low in vegetated streamside and inland areas, but they were much higher in inland areas devoid of plants. Nitrogen and phosphorus utilization byS. alterniflora was also investigated at an inland location in the salt marsh. Labelled ammonium-nitrogen and phosphate-phosphorus were added in May at a rate of 200 kg/ha to the soil of replicated plots. Added nitrogen significantly increased total above-ground plant biomass and plant height by 28 and 25%, respectively, 4 months after application. The ratio of belowground macro-organic matter to total aboveground biomass was decreased from 5.7 to 4.7 by the additional nitrogen. Added phosphorus did not significantly affect plant height and biomass. The use of15N-depleted nitrogen tracers showed that about half of the nitrogen in the aboveground portion ofS. alterniflora from 1 to 4 months after the nitrogen addition was derived from the added ammonium-nitrogen. After 4 months, 28 and 29% of the added labelled nitrogen was recovered in the aboverground and belowground biomass ofS. alterniflora, respectively. Recovery of added nitrogen was overestimated with a non-tracer method based on the difference in total nitrogen uptake between nitrogen-amended plots and untreated plots. Soil organic nitrogen comprised the majority of the nitrogen in the salt marsh. Nitrogen in the standing crop biomass ofS. alterniflora represented only about 2% of the total nitrogen in the plantsoil system of an inland marsh to a 20 cm soil depth.

The Role of Fishes in the Regulation of Phosphorus Availability in Lakes

Abstract: Several hypotheses concerning the contribution of fishes to nutrient dynamics in lakes were examined. The maximum quantity of excreted phosphorus by fishes was found to be negligible (< 0.33%) when compared to the demand for this element by the seston. Zooplankton (cladocerans and copepods) excretion supplied up to 12% of the daily summer orthophosphate requirements of the seston. The pool of total phosphorus present in the open water fish community was approximately equivalent to that present in the seston while the total phosphorus biomass in zooplankton was only 22 to 40% of that in the seston. Daily incorporation of total phosphorus into fish tissue and losses as fecal phosphorus could constitute up to 40% of total phosphorus in the seston lost due to sedimentation from the epilimnion depending on the feeding habits of the dominant fish species. Nutrient release due to the decomposition of fish carcasses supplied up to 20% of the allochthonous phosphorus entering the south basin in the spring. The pre...

Effect of germination, cooking, and canning on phosphorus and phytate retention in dry beans

Abstract: The effects of germination, cooking and canning on the changes in total phosphorus, inorganic phosphorus and phytate retention in black-eyed, red kidney, mung, and pink beans were determined in this study. Soaking the dry beans in water for 12 hr at 24°C resulted in a slight decrease in phytate. After germination for 96 hr or longer there was a significant breakdown in phytic acid, and an increase in inorganic phosphorus. Cooking the dry beans at 100°C for 3 hr had little effect on phytate retention. Heat processing the dry beans at 1155°C for 3 hr in cans resulted in some increase in inorganic phosphorus and a reduction in phytate.

Root Growth and Dry Matter Distribution of Soybean as Affected by Phosphorus Stress, Nodulation, and Nitrogen Source1

Abstract: gy reducing nitrate when NO3-N is the source of available N. Thus, for legumes able to form symbiotic associations with Rh izobium, the pattern of dry matter distribution (DMD) within the plant will differ depending upon its mode of N nutrition. The partitioning of dry matter between root and shoot is a heritable characteristic determined by the genotype of the plant (Andrews, 1939; Shank, 1943). Root morphology likewise is considered to be genetically determined (Smith, 1934; Zobel, 1975; Street, 1969). The expression of these characteristics can be altered by environmental conditions. Deficiencies of essential mineral nutrients have been shown to affect both the DMD within the plant and lateral root development. Plants deficient in N or P tend to accumulate relatively more dry matter in their roots than do plants which are adequately supplied (Turner, 1922; Brouwer, 1962). Weisum (1958) demonstrated that root branching in pea (Ptsum sattvum L.) was stimulated by nutrients as follows: NO3-N>P>K> Mg>Ca. Nitrate applied to a discrete root segment increased both the rate of lateral root extension and number of lateral roots per unit length of root (Hackett, 1972; Mdntyre and Raju, 1967; Drew, 1975). The establishment of an active N-fixing nodule system on the roots of a legume complicates these relationships. During the vegetative stage of growth, active root nodules utilize significant quantities of photosynthate for nodule growth and for N fixation (Minchin and Pate, 1972; Herridge and Pate, 1977). Summerfield et al. (1977) found that the root:shoot dry weight ratio in cowpea (Yigna unguiculata L. Walp.) was larger in nonnodulated plants than in nodulated plants grown at equivalent levels of applied N. Experiments with red clover (Trifolium pratense L.) and barrel medic (Medicago tribuloides Desr.) indicate that there is an inverse relationship between nodule number and lateral root formation (Nutman, 1948; Dart and Pate, 1959). Also, there are qualitative observations concerning differences between the root morphology of grain legumes provided combined N and those which are effectively nodulated (Weber, 1966; Wych and Rains, 1978). The purpose of this study was to define the changes in DMD and root development in the soybean plant as influenced by the mode of N nutrition, the magnitude of root nodulation, and P deficiency. ABSTRACT

Dynamics of phosphorus and organic matter during leaf decomposition in a forest stream

Abstract: Leaf decomposition rates and changes in leaf phosphorus content during decomposition were followed for one year at six sites in Bear Brook, a forest stream in New Hampshire. Experimental leaf packs consisted of 3 g each of sugar maple, yellow birch, and beech leaves enclosed in 1 mm mesh bags. Leaf decay was slowest in sites where sediment deposition was high and most rapid in sites where sediment deposition was low. There was no correlation between decay rate and numbers or biomass of invertebrates. Leaf phosphorus content increased during decomposition, and the increase was greatest where sediment deposition was greatest. Organic matter losses from a stream can be partitioned into losses due to export downstream and losses due to biological processes. Estimates of biological loss rates obtained using a mass balance approach were slightly lower than estimates obtained using experimental leaf packs.

Effect of dietary protein and phosphorus levels on the utilization of zinc, copper and manganese by adult males.

Abstract: Zinc, copper and manganese utilization were examined in eight adult males fed a low protein-moderate phosphorus diet (LPrMP), a low protein-high phosphorus diet (LPrHP), a high protein-moderate phosphorus diet (HPrMP) and a high protein-high phosphorus diet (HPrHP) during a 51-day balance study. The low and high protein diets contained 8.1 g and 24.1 g nitrogen daily, respectively. The moderate and high levels of phosphorus were 1,010 and 2,525 mg phosphorus daily. Subjects lost less zinc in the feces when fed the HPrMP diet than when fed the other three diets. The level of dietary protein and phosphorus all statistically affected fecal zinc excretion. Urinary zinc excretion was significantly greater when subjects consumed the high protein diets rather than the low protein diets. Apparent retention of zinc was greatest when subjects were fed the HPrMP diet rather than the other three diets. This effect was statistically attributable to the interaction between dietary protein and phosphorus. Serum zinc levels were significantly elevated when subjects consumed the high protein rather than the low protein diets. Serum zinc levels were correlated to urinary zinc excretion (r = 0.788, P< 0.001), apparent retention of zinc (r = 0.385, P< 0.05) and serum copper levels (r = 0.395, P < 0.05). Apparent absorption and retention of copper were significantly greater when subjects were fed the high protein rather than the low protein diets. They dietary treatments did not affect the urinary excretion of copper, serum copper levels or the apparent absorption and retention of manganese by these subjects.

Availability of phosphorus to phytoplankton and its implications for phosphorus management strategies 1

Abstract: One of the questions associated with the development of a cost-effective phosphorus management strategy for a waterbody concerns whether the control program should be based on total phosphorus or on algal available phosphorus entering the waterbody. Until now, eutrophication control programs have been based largely on the control of any form of phosphorus that was amenable to control, irrespective of whether the phosphorus was in a form which could support algal growth.

Nutrient Cycling in a Eucalyptus Obliqua (L'hérit.) Forest [in Victoria]. Iv. Nutrient Uptake and Nutrient Return

Abstract: Uptake of phosphorus, potassium, magnesium, and calcium by mature Eucalyptus obliqua forest was measured over a period of 22 years. during which the forest reached maximum net annual primary production. The concentration of phosphorus in components of the trees was less than that recorded for other tree species, while the concentrations of the other nutrients in E. obliqua were similar to those in other trees. Since the biomass of E. obliqua is typical of temperate evergreen forests, the total mass of phosphorus in the stand is less than that found in other forests. Gross annual demand of the stand over the 22-year period 1955-1977 decreased in the order calcium > potassium > magnesium > phosphorus. The gross annual demand for phosphorus is 0.298 g m-2 year-1 of which 46% is supplied by biochemical cycling and 36% is supplied by biogeochemical cycling. Since the geochemical input of phosphorus is insignificant, the remaining 18%, or 0.054 g m-2 year-1, must be supplied from soil reserves. At the other extreme, gross annual demand for calcium is 3.37 g m-2 year-1 of which 82% is supplied by biogeochemical cycling and only 2% by biochemical cycling. Since the balance of the geochemical cycle of calcium supplies 0.11 g m-2 year-1 to the forest, the remaining 0.44 g m-2 year-1 is supplied from soil reserves. Annual demand for all nutrients increased slightly as the forest aged, but the proportion of this demand supplied by both biochemical cycling and biogeochemical cycling also increased. The annual supply of nutrients to the stand from available sources in the soil therefore decreased with increasing age. A major contribution to biochemical cycling is shown to result from heartwood formation; the sapwood-heartwood transition accounts for 31% of the total biochemical cycle of phosphorus. Comparison with other forests suggests that the eucalypt is no more efficient at keeping phosphorus within the stand than are other genera. The low concentrations of phosphorus in the eucalypt stand therefore suggest a low absolute requirement for phosphorus.