Primary production in ten reservoirs in southern Brazil

The growth and phosphatase activity during phosphorus starvation of cultures of Nodularia spumigera Mertens were examined. Stationary phase was reached much sooner in phosphorus-deficient cultures than in phosphorus-sufficient cultures; the growth rate did not change. Phosphatase activities were greatly increased in stationary phase. Diurnal patterns were established for phosphorus-sufficient cultures, but they were not light related. In phosphorus-deficient cultures, an increase in phosphatase activities over a 24 h period was superimposed on a diurnal pattern. Both phosphorus and nitrogen additions lowered the relative phosphatase activities in long term studies, but the effect of phosphorus was much more pronounced. In short term studies, phosphorus appeared to cause an immediate decrease in phosphatase activity, but did not affect phosphatase activity after that for up to 24 h. Nitrogen did not have any short term effect on phosphatase. Phosphatase activity was correlated with changes in the proportion of TCA-insoluble phosphorus (polyphosphates).     

Biological actions of human and rat calcitonin and calcitonin gene-related peptide

We assessed the central and peripheral biological actions of human and rat calcitonin and calcitonin gene-related peptide (CGRP). After intravenous administration, human and rat calcitonin, but neither human nor rat CGRP significantly decreased plasma calcium and phosphorus concentrations in awake, freely moving rats. After intracerebroventricular as well as after intravenous administration, human and rat calcitonin and human and rat CGRP significantly inhibited gastric acid secretion in conscious rats. Intracerebroventricular administration of rat calcitonin did not alter plasma calcium and phosphorus concentrations. Linear, partially protected CGRP and calcitonin did not exhibit any biological effects. These studies indicate that calcitonin, but not CGRP, affects calcium and phosphorus homeostasis while both peptides decrease gastric acid secretion similarly. Furthermore, these studies support the hypothesis that the calcium and phosphorus lowering effects of calcitonin are peripheral while the gastric inhibiting actions of the calcitonin and CGRP are mediated by the central nervous system.     

Effect of Phosphorus on survival of Escherichia coli in drinking water biofilms

The effect of phosphorus addition on survival of Escherichia coli in an experimental drinking water distribution system was investigated. Higher phosphorus concentrations prolonged the survival of culturable E. coli in water and biofilms. Although phosphorus addition did not affect viable but not culturable (VBNC) E. coli in biofilms, these structures could act as a reservoir of VBNC forms of E. coli in drinking water distribution systems.     

Dietary phosphorus availability influences female cricket lifetime reproductive effort

1. Recent ecological stoichiometric findings indicate that the relationships among key macronutrient elements [e.g. carbon (C), nitrogen (N), and phosphorus (P) of organisms and their resources] may underlie variation in life‐history traits. The amount of phosphorus in an individual's body is often correlated with its rate of growth, and low‐phosphorus diets are known to reduce growth in a number of insect and crustacean herbivores. 2. These findings suggest that the stoichiometric imbalance between organismal biomass requirements and the relative scarcity of nutrients in nature may also underlie variation in lifetime reproductive success. 3. This study investigated how dietary phosphorus availability during adulthood influenced lifetime reproductive effort, compensatory feeding, lifespan, condition, and stoichiometry of adult European House Cricket, Acheta domesticus. 4. Female crickets fed high amounts of phosphorus during adulthood laid significantly more eggs compared to those fed low amounts of phosphorus. Phosphorus availability did not directly influence lifespan, condition, or body stoichiometry, and crickets did not compensate for low phosphorus diets by eating more food. 5. A stoichiometric perspective may help understand the causes of variation in invertebrate fitness.     

不同施磷量对春油菜产量和土壤磷素平衡的影响

青海省东部春油菜主产区的土壤速效磷含量高、磷肥施用量大、磷肥利用率低。研究不同施磷量对春油菜的生长、磷素吸收和利用、土壤磷素平衡的影响,可为该地区春油菜田养分高效管理提供科学依据,对保障青藏高原农业可持续发展具有重要意义。本研究于2017和2018年在青海省互助县开展了田间试验,设置0、30、60、90、120 kg P₂O₅·hm^-2 5个磷肥施用量,测定了不同处理春油菜的产量、磷素吸收与利用、籽粒含油率等。结果表明: 2017年施磷量60 kg·hm^-2处理的油菜籽粒产量、成熟期地上部磷素累积量和产油量均显著高于不施磷处理,但施磷量超过60 kg·hm^-2后,籽粒产量和产油量不再增加;2018年施磷量对春油菜籽粒产量、成熟期地上部磷素累积量和产油量均无显著影响。两年度的磷肥表观利用率均很低,平均为6.7%。施用磷肥条件下土壤均有不同程度的磷素盈余,施磷量低于60 kg·hm^-2时盈余量较低。综合考虑春油菜产量、产油量、磷肥表观利用率和土壤磷素表观平衡,在青海省东部春油菜区,推荐施磷量为60 kg·hm^-2。     

Micronutrient and phosphorus limitation of phytoplankton abundance in Gem Lake,Sierra Nevada,California

Nutrient addition experiments conducted during the ice-free seasons of 1983 and 1984 in Gem Lake, an alpine lake in the Sierra Nevada mountains of California, indicate that algal biomass is limited by phosphorus, in combination with iron or copper. Phosphorus additions were always required to stimulate growth, but did not do so when phosphorus was the only nutrient added. Simultaneous additions of phosphorus and iron resulted in increased levels of chlorophyll, particulate carbon, particulate nitrogen and particulate phosphorus. Simultaneous additions of phosphorus and copper resulted in increases in chlorophyll, particulate nitrogen and particulate phosphorus, not in particulate carbon. Neither iron nor copper by itself stimulated growth.Particulate N : P ratios from all seasons in Gem Lake suggest that simultaneous micronutrient and phosphorus limitation exists throughout the summer, when nutrient and biomass levels remain low; limitation by phosphorus alone may appear in the fall and spring, when biomass and major ion concentrations increase dramatically.     

Effects of fertilization and herbicides on growth of young loblolly pine and infestations of Nantucket pine tip moth（Lepidoptera： Tortricidae）

A 2-year-old pine plantation was selected to receive treatments of fertilizers and herbicides to evaluate effects on Nantucket pine tip moth infestations and the tree growth parameters of height, diameter and volume increment. Nitrogen and phosphorus fertilizers, and hexazinone and sulfometuron methyl herbicides were used in creating six treatments： （i） control; （ii） phosphorus; （iii） nitrogen and phosphorus; （iv） phosphorus and herbicide; （v） nitrogen, phosphorus and herbicide; and （vi） herbicide. Treatments were applied in 1987 and 1988. In 1987, trees treated with nitrogen, phosphorus and herbicide had significantly greater height, diameter and volume growth than trees not receiving fertilizer treatments, but did not have significantly higher tip moth infestations than control trees. Treatments receiving phosphorus only had much lower tip moth infestation rates than other treatments except nitrogen and phosphorus. In 1988, tip moth infestations were uniformly low, with no differences in treatment effects observed.     

Carbohydrate metabolism and phosphorus/salinity interactions in wheat (Triticum aestivum L.)

Foliar inorganic ion and carbohydrate concentrations were determined in wheat plants treated with factorial combinations of phosphorus fertilizer and NaCl in a glasshouse experiment. Growth reductions and visual symptoms of salt toxicity were minimized when phosphorus nutrition was adequate, and were intensified by phosphorus deficiency. Foliar sodium and chloride accumulated up to 4.0–5.5% d.w. with salinity treatment. However, ionic concentrations within corresponding leaves or distributions between leaves of plants with different phosphorus treatments were not influenced by phosphorus treatment and had no relationship to the severity of salt toxicity symptoms. This suggests that phosphorus deficiency reduced the cellular tolerance for ion accumulation. A combination of phosphorus deficiency and salinity induced an accumulation of foliar starch and sucrose despite substantial reductions in net CO₂ assimilation rates. This accumulation did not occur if phosphorus nutrition was adequate, which is consistent with the roles of phosphorus in carbohydrate metabolism. It is proposed that adequate phosphorus nutrition is essential for effective ion compartmentation by contributing to efficient carbohydrate utilization in salt-stressed wheat.     

Degradation of organophosphonates by Penicillium citrinum

Utilization of organophosphonates as the sole source of phosphorus, carbon or nitrogen by a soil isolate of Penicillium citrinum was studied. Penicillium citrinum was found to utilize 2-aminoethylphosphonic and 2-oxoalkylphosphonic acids as the sole phosphorus source whereas 1-hydroxyalkylphosphonates as well as 1-aminoalkylphosphonates and their dipeptides did not support the growth of the fungus. The mould did not metabolize any of the phosphonates tested, when they served as the sole carbon or nitrogen source.
Penicillium citrinum is perhaps the first mould strain isolated from soil, shown to be capable of organophosphonate degradation.     

Effect of Phosphorus on Survival of Escherichia coli in Drinking Water Biofilms

The effect of phosphorus addition on survival of Escherichia coli in an experimental drinking water distribution system was investigated. Higher phosphorus concentrations prolonged the survival of culturable E. coli in water and biofilms. Although phosphorus addition did not affect viable but not culturable (VBNC) E. coli in biofilms, these structures could act as a reservoir of VBNC forms of E. coli in drinking water distribution systems.     

Changes in extractable organic phosphorus in soil in the presence and absence of plants

Summary The effect of cropping on soil organic phosphorus was investigated in laboratory and greenhouse work with six soils. Successively lower contents of extractable organic phosphorus were found in samples that had been (a) airdried initially and stored in that condition, (b) incubated in a moist condition but without a crop, and (c) planted to four successive crops, the roots of the crops being removed before analysis of the soil. These differences were statistically significant. Samples of rhizosphere soil taken after the fourth crop did not yield significantly different amounts of extractable organic phosphorus than did bulk samples of cropped soil taken at the same time. Extractable organic and inorganic phosphorus in the soils were not significantly affected by drying the soil before each crop.Journal Paper No. J-5916 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.Former Rockefeller Fellow and Professor, respectively. The senior author is now Associate Professor, Department of Soils, Punjab Agricultural University, Ludhiana, Punjab.     

Metabolic balance studies in patients with Paget's disease receiving salmon calcitonin over long periods.

Metabolic balance and calcium kinetic studies were performed in four patients with Paget''s disease before treatment with salmon calcitonin and during the early and late stages of the treatment, which lasted 9 to 19 months, A significant decrease in bone turnover and 24-hour urine hydroxyproline and serum alkaline phosphatase values was observed in all patients. In contrast, the calcium, phosphorus and magnesium balances did not change significantly. In agreement with this, the partial body calcium, measured by in vivo neutron activation analysis, did not change. Intestinal calcium absorption increased initially, but returned to baseline levels 9 to 19 months after the study began. During the initial period there was a small, significant, but transient decrease in tubular reabsorption of phosphorus; this was accompanied by a significant decrease in serum phosphorus values--probably a direct effect of calcitonin rather than evidence of secondary hyperparathyroidism. Administration of salmon calcitonin to patients with Paget''s disease decreases bone turnover without affecting calcium and phosphorus balances.     

Nitrogen regulation of acid phosphatase in Neurospora crassa.

Neurospora crassa possesses a repressible acid phosphatase with phosphodiesterase activity which appears to permit it to utilize ribonucleic acid as a phosphorus and as a nitrogen source. This acid phosphatase, which is specified by the pho-3 locus, is derepressed approximately eightfold during nitrogen limitation and to an even greater extent during phosphorus limitation, but is unaffected by sulfur limitation. Derepression of the enzyme did not occur when adenosine 5'-monophosphate was the sole phosphorus or nitrogen source. Synthesis of the acid phosphatase is not under the control of the nit-2 locus, which regulates the expression of a large number of other nitrogen catabolic enzymes. The structural gene of the acid phosphatase appears to be a member of both the phosphorus and nitrogen regulatory circuits.     

Aluminum sulfate treatment: Short-term effect on complex phosphorus compounds in a eutrophic lake

Application of aluminum sulfate to the hypolimnion of West Twin Lake, a hardwater eutrophic lake in northeastern Ohio, did not efficiently remove complex phosphorus compounds from the water column. The majority of the complex phosphorus compounds remaining after alum treatment released P0₄ following brief treatment with alkaline phosphatase.     

Water quality research in the Loosdrecht lakes: proposals for the follow-up restoration measures

Reduction of the external phosphorus load in 1984 did not lead to recovery of Loosdrecht lakes. Therefore the Provincial Water Authorities of the Province of Utrecht proposed, after consulting the research group Water Quality Research Loosdrecht lakes (WQL), measures to reduce the present external phosphorus loading from 0.35 to 0.1 g Pm^–2y^–1. Mathematical modelling suggested that such a reduction would benefit the water quality of the lakes. The results of the WQL investigation did not lead to additional measures (dredging, biomanipulation, chemomanipulation).     

Effect of phosphorus on polymyxin B biosynthesis by B. polymyxa 1538 on media of varying makeup]

The effect of phosphorus on biosynthesis of polymyxin B by B. polymyxa 1538 was studied and its optimal concentration in the synthetic and two complex media was determined. Correlation between the culture growth and consumption of the main components, on the one hand, and concentration of phosphorus in the medium, on the other hand, was found. It was shown that the effect of phosphorus on biosynthesis of polymyxin B did not depend on the carbon source in the medium and aeration conditions.     

The efficiency of Arabidopsis thaliana (Brassicaceae) root hairs in phosphorus acquisition

Arabidopsis thaliana root hairs grow longer and denser in response to low-phosphorus availability. In addition, plants with the root hair response acquire more phosphorus than mutants that have root hairs that do not respond to phosphorus limiting conditions. The purpose of this experiment was to determine the efficiency of root hairs in phosphorus acquisition at high- and low-phosphorus availability. Root hair growth, root growth, root respiration, plant phosphorus uptake, and plant phosphorus content of 3-wk-old wild-type Arabidopsis (WS) were compared to two root hair mutants (rhd6 and rhd2) under high (54 mmol/m) and low (0.4 mmol/m) phosphorus availability. A cost-benefit analysis was constructed from the measurements to determine root hair efficiency. Under high-phosphorus availability, root hairs did not have an effect on any of the parameters measured. Under low-phosphorus availability, wild-type Arabidopsis had greater total root surface area, shoot biomass, phosphorus per root length, and specific phosphorus uptake. The cost-benefit analysis shows that under low phosphorus, wild-type roots acquire more phosphorus for every unit of carbon respired or unit of phosphorus invested into the roots than the mutants. We conclude that the response of root hairs to low-phosphorus availability is an efficient strategy for phosphorus acquisition.     

Phosphorus and light colimit periphyton growth at subsaturating irradiances

1. This study investigated the combined effects of light and phosphorus on the growth and phosphorus content of periphyton. To investigate the potential for colimitation of algal growth by these two resources, diatom‐dominated periphyton communities in large flow‐through laboratory streams were exposed under controlled conditions to simultaneous gradients of light and phosphorus. 2. Periphyton growth rate was predictably light‐limited by the subsaturating irradiances (12–88 μmol photons m^?2 s^?1) used in this experiment. However, phosphorus concentration also limited growth rate: growth increased hyperbolically with increasing soluble reactive phosphorus (SRP), reaching a threshold of growth saturation between 22 and 82 μg L^?1. 3. Periphyton phosphorus content was strongly and nonlinearly related with SRP, reaching a maximum at 82 μg L^?1 SRP. Contrary to the Light : Nutrient Hypothesis, periphyton phosphorus content did not decrease with increasing light, even at the lowest concentrations of SRP. Periphyton phosphorus was highly correlated with periphyton growth rate (Spearman's ρ = 0.63, P < 0.005). 4. Multiple regression analysis reinforced evidence of simultaneous light and phosphorus limitation. Both light and periphyton phosphorus content were significant variables in multiple regressions with growth parameters as dependent variables. Light alone accounted for 67% of the variance in periphyton biomass, and the addition of periphyton phosphorus as an additional independent variable increased the total amount of variance explained to 81%. 5. Our results did not support the hypothesis that extra phosphorus is required for photoacclimation to low light levels. Rather, the effect of additional phosphorus may have been to accommodate increased requirements for P‐rich ribosomal RNA when growth was stimulated by increased light. The potential colimitation of periphyton growth by phosphorus and light at subsaturating irradiances has important implications in both theoretical and applied aquatic ecology.     

Mycorrhizae and soil phosphorus affect growth of <Emphasis Type="Italic">Celastrus orbiculatus</Emphasis>

Celastrus orbiculatus is an exotic liana that exploits disturbed areas in the eastern United States and once established, can invade into relatively undisturbed forest ecosystems. Mechanisms facilitating its invasion are not fully understood, including whether associations with mycorrhizal fungi are related to its invasion success. We grew C. orbiculatus in a greenhouse and compared growth responses when mycorrhizal fungi or a fungistatic were added to growth media that was either phosphorus-limiting or non-limiting. Results indicated C. orbiculatus forms association with native endomycorrhizal but not with native ectomycorrhizal fungi regardless of phosphorus level. Plants grown with sufficient phosphorus had significantly higher above-ground morphological and physiological traits but significantly lower root biomass compared to plants grown in low phosphorus conditions. Although above-ground traits did not vary significantly between mycorrhizal versus fungistatic added treatments, root biomass was significantly less in plants inoculated with mycorrhizae compared to plants receiving fungistatic. Under low phosphorus conditions, mycorrhizae appeared to be beneficial to the plant although being mycorrhizal did not fully compensate for insufficient phosphorous in the greenhouse situation where pot size limited soil exploration. Our results suggest that in the presence of mycorrhizae or sufficient phosphorus, C. orbiculatus can respond by preferentially allocating energy to above-ground growth, thus supporting its liana growth form onto trees and allowing the exotic to outcompete native species for light resources. If mycorrhizal fungi aid in acquisition of phosphorus, this association could be related to the invasion success of C. orbiculatus.     

Regulation of two phosphatases and a cyclic phosphodiesterase of Salmonella typhimurium.

The regulation of three Salmonella typhimurium phosphatases in reponse to different nutritional limitations has been studied. Two enzymes, an acid hexose phosphatase (EC 3.1.3.2) and a cyclic phosphodiesterase (EC 3.1.4.d), appear to be regulated by the cyclic adenosine 3' ,5'-monophosphate (AMP) catabolite repression system. Levels of these enzymes increased in cells grown on poor carbon sources but not in cells grown on poor nitrogen or phosphorus sources. Mutants lacking adenyl cyclase did not produce elevated levels of these enzymes in response to carbon limitation unless cyclic AMP was supplied. Mutants lacking the cyclic AMP receptor protein did not produce elevated levels of these enzymes in response to carbon limitation regardless of the presence of cyclic AMP. Since no specific induction of either enzyme could be demonstrated, these enzymes appear to be controlled solely by the cyclic AMP system. Nonspecific acid phsphatase activity (EC 3.1.3.2) increased in response to carbon, nitrogen, phosphorus, or sulfur limitation. The extent of the increase depended on growth rate, with slower growth rates favoring greater increases, and on the type of limitation. Limitation for either carbon or phosphorus resulted in maximum increases, whereas severe limitation of Mg2+ caused only a slight increase. The increase in nonspecific acid phosphatase during carbon limitation was apparently not mediated by the catabolite repression system since mutants lacking adenyl cyclase or the cyclic AMP receptor protein still produced elevated levels of this enzyme during carbon starvation. Nor did the increase during phosphorus limitation appear to be mediated by the alkaline phosphatase regulatory system. A strain of Salmonella bearing a chromosomal mutation, which caused constitutive production of alkaline phosphatase (introduced by an episome from Escherichia coli), did not have constitutive levels of nonspecific acid phosphatase.