Total Po Research Articles

Reaction of Banana Hybrids (Phase-II) for Resistance toMeloidogyne incognita

Plant parasitic nematodes are one of the major biotic stresses affecting banana production. Breeding works carried out at the Department of Fruit crops, Tamil Nadu Agricultural University (TNAU), India. The potential diploids and hybrids developed were crossed with commercial triploids to develop primary tetraploids and improved diploids. The susceptible check cultivar used was Rasthali (AAB), while the resistant reference cultivar used Pisang Lilin (AA). Banana suckers of uniform size and weight were collected, pared and planted in earthen part containing 5 kg sterilized pot mixture. Egg masses of M. incognita were picked from roots, allowed to hatch in a beaker of distilled water and the hatched juveniles (J2) were inoculated in the rhizosphere of the hybrids by soil injection method @ 5,000 nematodes/pot. Same set of replicated banana hybrids were also maintained as uninoculated check. The reactions of nineteen new synthetic banana phase II hybrids to Meloidogyne incognita was studied under field conditions as well as in controlled inoculation tests in pots. Hybrid H 531 (Poovan x Pisang Lilin) was found to be resistant and six hybrids, H-02-34, H-03-05, H-03-13, H-04-12, H-04-24 and NPH-02-01 were found to be toterant to the root-knot nematode, Meloidogyne incognita while the remaining were rated as susceptible and highly susceptible ones. Total phenols and PO, PPO, PAL and enzymatic activity of the hybrids in defense mechanism in response to nematode invasion indicated higher activities in resistant genotypes compare to susceptible ones. Hybrid H 531 had the maximum biochemical content and enzyme activity among the hybrids included in this study. The resistant and tolerant hybrids had enhanced contents of total phenol, PO, PPO and PAL.

Chemical and Geological Control on Surface Water within the Shade River Watershed in Southeastern Ohio

The under-sampled middle and western branches of Shade River Watershed (SRW) in SE Ohio were investigated as part of the Ohio University—U.S. Environmental Protection Agency (EPA) STAR grant. This project was for monitoring the quality of watersheds in Ohio and classifying them according to their physical, chemical, and biological conditions. Water samples, as well as field parameters, were taken at twenty-two sites for chemical analyses. The ions analyzed included Ca, Mg, Na, Fe, Mn, Al, NO3, SO4, HCO3, and total PO4, while the field parameters measured included pH, dissolved oxygen (DO), total dissolved solids (TDS), electrical conductivity (EC), and alkalinity. To assess the water quality within the SRW, the analyzed ions and field parameters were compared to the USEPA criteria for the survival of aquatic life. Analytical results showed that the watershed is dominated by Ca-HCO3waters with DO, Fe, Mn, and PO4being the main causes of impairment within the streams. The relatively elevated concentrations of manganese and less extent iron may be associated with the local geology and the acidic nature of the soils. The high alkalinity and calcium concentrations are due to the limestone geology. The elevated phosphate concentration may be due to anthropogenic sources, fertilizers, or contributions from phosphorus-rich bedrock that differs geochemically from other areas.

Examining and Modelling the Influence of Lengths of Rebars in Concrete to Shapes of Impedance Spectra

A comparative analysis of the results of impedance tests of two series of concrete specimens with various lengths of reinforcement in a state of passivation and corrosion was conducted. Impedance plots were found in the clear trends in the shapes of impedance spectra of the reinforcement as a function of its length. With the aim of explaining the observed phenomena there was developed a model of the steelconcrete system with parallel-connected equivalent electrical circuits. The model allows the simulation of the formation of impedance spectra characterizing any length of reinforcement in concrete, using a counter electrode placed on the outer surface of the concrete cover. The model impedance spectra were obtained after taking into account two groups of electrochemical parameters characterizing, by analogy with experimental testing, reinforcing steel in a state of passivation and corrosion. The conducted model simulation of the influence of various lengths of reinforcement, assuming the total polarization of the areas, confirmed the observed trends in experimental studies of changes in impedance spectra shapes of reinforcing steel in concrete. Straipsnyje pateikta lyginamoji dviejų serijų betoninių bandinių su įvairių ilgių armatūra, esančių pasyvavimo ir korozijos būklės, analizė. Atliekant tyrimus nustatytos armatūros spektro kreivės kaip funkcijos tarp jų ilgio. Siekiant paaiškinti tiriamą fenomeną, buvo sukurtas plieno ir betono sistemos su lygiagrečiai sujungta elektros grandinės schema modelis. Juo remiantis galima modeliuoti armatūros betone spektro formavimąsi atsižvelgiant į jos ilgį, naudojant elektrodo skaitiklį, uždėtą ant betono apsauginio sluoksnio išorės. Nepriklausomas armatūros spektras buvo nustatytas eksperimentiškai įvertinant du eletrocheminius parametrus: armatūros pasyvavimą ir koroziją. Siūlomas modelis, įvertinant skirtingus armatūros strypų ilgius ir jų poliarizacijos plotą, buvo patvirtintas eksperimentiškai nustatytomis armatūros betone spektro kreivėmis.

Influence of impregnation ratio on coffee ground activated carbon as landfill leachate adsorbent for removal of total iron and orthophosphate

Coffee grounds waste was used to prepare activated carbon with particle size between 1.18 and 2 mm by chemical activation with sulphuric acid. The influence of impregnation ratio on physical properties of activated carbon and removal efficiency of total iron and orthophosphate (PO 4–P) was studied. Impregnation ratio of 0.5 was found optimum for preparing activated carbon with high pore surface area (224.7 m 2/g) and micropore volume (0.07986 cm 3/g). Batch experiments were conducted to study the effects of contact time, pH, particle size and adsorbent dosage. Impregnation ratios of 2.5 and 0.5 were found to be optimum for the adsorption of total iron and PO 4–P, respectively at doses of 10 g and pH 8.1. pH 13 was optimum for iron removal while pH < 5 and > 11 was optimum for PO 4–P removal. The adsorption capacity increased with increasing adsorbent dosage for total iron. However, this trend was exceptional for PO 4–P with fluctuating adsorption capacity. The smaller particle size yielded larger adsorption capacity.

Vasopressin-dependent coupling between sodium transport and water flow in a mouse cortical collecting duct cell line

Water balance is achieved through the ability of the kidney to control water reabsorption in the connecting tubule and the collecting duct. In a mouse cortical collecting duct cell line (mCCD(c11)), physiological concentrations of arginine vasopressin increased both electrogenic, amiloride-sensitive, epithelial sodium channel (ENaC)-mediated sodium transport measured by the short-circuit current (Isc) method and water flow (Jv apical to basal) measured by gravimetry with similar activation coefficient K(1/2) (6 and 12 pM, respectively). Jv increased linearly according to the osmotic gradient across the monolayer. A small but highly significant Jv was also measured under isoosmotic conditions. To test the coupling between sodium reabsorption and water flow, mCCD(c11) cells were treated for 24 h under isoosmotic condition with either diluent, amiloride, vasopressin or vasopressin and amiloride. Isc, Jv, and net chemical sodium fluxes were measured across the same monolayers. Around 30% of baseline and 50% of vasopressin-induced water flow is coupled to an amiloride-sensitive, ENaC-mediated, electrogenic sodium transport, whereas the remaining flow is coupled to an amiloride-insensitive, nonelectrogenic sodium transport mediated by an unknown electroneutral transporter. The mCCD(c11) cell line is a first example of a mammalian tight epithelium allowing quantitative study of the coupling between sodium and water transport. Our data are consistent with the 'near isoosmotic' fluid transport model.

Cytarabine and Etoposide (CYVE) as First-Line Therapy for Primary Central Nervous System Lymphoma

AbstractAbstract 4895 Background:The treatment of primary central nervous system lymphoma (PCNSL) is characterized by high rates of toxicity and intracranial relapse despite initial response. High-dose methotrexate (HD-MTX), with or without cranial irradiation, has become the standard of care; combining this with other chemotherapeutic agents has improved complete remission rates but at the expense of increased treatment-related adverse events, particularly haematologic and neurologic toxicity. Cytarabine has been used in combination with etoposide (CYVE) as a salvage therapy for patients who have been refractory to or relapsed after HD-MTX-based regimens (Soussain C et al, J. Clin. Oncol. 2001; Soussain C et al, J. Clin. Oncol. 2008). In these studies, cytarabine was given as an infusion at a dose of 50mg/m2/d over 12 hours on days 1–5, and at a dose of 2g/m2/d over 3 hours on days 2–5 with etoposide at 200mg/m2/d on days 2–5. Both responders and non-responders were eligible to proceed to autologous stem cell transplant (autoSCT) using a conditioning regimen of thiotepa 250mg/m2/d on days -9 to -7, busulfan 10mg/kg total dose po or 8mg/kg total dose iv over days -6 to -4, and cyclophosphamide 60 mg/m2/d on days -3 to -2. Median OS was 58.6 months in patients able to undergo autoSCT, but with significant neurotoxicity that may have been related in part to prior therapies. Methods and Results:Given its excellent CNS penetration, CYVE may be an effective regimen in previously untreated patients, with lower risk of neurotoxicity. We have used CYVE as a first-line therapy for patients with PCNSL who are potentially eligible for subsequent autoSCT. Between January 1, 2005 and December 31, 2009, 7 patients with a diagnosis of PCNSL were treated with first-line CYVE using the regimen described above. All were HIV negative, showed no disease outside of the CNS on bone marrow biopsy and staging CT or PET scan, and had biopsy-proven PCNSL with diffuse large B-cell histology. Median age was 55 (42-61) with 4 female and 3 male patients. Median International Extranodal Lymphoma Study Group Prognostic Index score was 2 (0-2), although in actuality may have been higher, as 4 patients were not able to undergo lumbar puncture at diagnosis. ECOG status was < 2 in 3 patients, ≥ 2 in 3 patients, and not documented in 1 case. Patients received a median of 2 cycles of CYVE (1-3), with 2 receiving concurrent rituximab and the 1 patient with intra-ocular lymphoma receiving post-adjuvant orbital radiation. No cranial radiation was administered. Five patients achieved CR and proceeded to autoSCT. Two patients had a PR but later died of progressive disease at day +48 and day +117, respectively. In both cases, however, the patients were suspected of having disease long before they were treated with CYVE. The first had presented 3 years prior to the diagnosis with a solitary brain lesion that resolved with decadron monotherapy before pathologic documentation. The second had had a brain biopsy that failed to show malignant disease 4 months before the PCNSL diagnosis was confirmed and treatment initiated. Median OS and PFS for the group have not yet been reached with mean follow-up of 657 days. Among the 5 patients who achieved CR, all patients remain alive in CR with a mean follow-up of 841 days (320-1262 days), or 28 months. Toxicities included at least 1 episode of febrile neutropenia in all 7 patients, 2 possible but unconfirmed cases of pulmonary aspergillosis, 2 cases of drug-induced hepatitis (with ALT > 3x ULN), 1 case of toxic epidermal necrolysis secondary to imipenem use during an episode of febrile neutropenia, 1 small bowel obstruction requiring surgical intervention, and 1 case of late grade 2 neurotoxicity presenting 3 years after treatment. Conclusions:In this small cohort of patients, first-line CYVE has shown to be highly effective (ORR 100%, CR 71%) with minimal long-term toxicity compared to that which is seen using it as a salvage therapy. When followed by autoSCT, long-term survival with preserved quality of life may be possible. A prospective study would be necessary to confirm these initial results in practice. Disclosures:No relevant conflicts of interest to declare.

PmPPAE2, a new class of crustacean prophenoloxidase (proPO)-activating enzyme and its role in PO activation

The prophenoloxidase (proPO) activating system plays an important role in the defense against microbial invasion in invertebrates. In the present study, we report a second proPO-activating enzyme (designated PmPPAE2) from the hemocytes of the black tiger shrimp, Penaeus monodon. PmPPAE2 contained the structural features of the clip domain serine proteinase family and exhibited 51% amino acid sequence similarity to the insect Manduca sexta PAP-1. Amino acid sequence alignment with the available arthropod PPAE sequences demonstrated that PmPPAE2 is a new class of crustacean PPAE. Transcript expression analysis revealed that PmPPAE2 transcripts were mainly expressed in hemocytes. Double-stranded RNA-mediated suppression of PmPPAE2 transcript levels resulted in a significant decrease in the total hemolymph PO activity (41%) and also increased the shrimp's susceptibility to Vibrio harveyi infection. Genomic organization analysis revealed that PmPPAE1 and PmPPAE2 are encoded by different genomic loci. The PmPPAE1 gene consists of ten exons and nine introns, whilst PmPPAE2 comprises of eight exons interrupted by seven introns. Analysis of the larval developmental stage expression of the four key genes in the shrimp proPO system ( PmPPAE1, PmPPAE2, PmproPO1 and PmproPO2) revealed that PmPPAE1 and PmproPO2 transcripts were expressed in all larval stages (nauplius, protozoea, mysis and post-larvae), whilst PmPPAE2 and PmproPO1 transcripts were mainly presented in the late larval developmental stages (mysis and post-larvae). These results suggest that the PmPPAE2 functions as a shrimp PPAE and possibly mediates the activation of PmproPO1.

Variations of immune parameters in terrestrial isopods: a matter of gender, aging and Wolbachia

Ecological factors modulate animal immunocompetence and potentially shape the evolution of their immune systems. Not only environmental parameters impact on immunocompetence: Aging is one major cause of variability of immunocompetence between individuals, and sex-specific levels of immunocompetence have also been frequently described. Moreover, a growing core of data put in light that vertically transmitted symbionts can dramatically modulate the immunocompetence of their hosts. In this study, we addressed the influence of gender, age and the feminising endosymbiont Wolbachia (wVulC) on variations in haemocyte density, total PO activity and bacterial load in the haemolymph of the terrestrial isopod Armadillidium vulgare. This host-symbiont system is of particular interest to address this question since: (1) wVulC was previously shown as immunosuppressive in middle-aged females and (2) wVulC influences sex determination. We show that age, gender and Wolbachia modulate together immune parameters in A. vulgare. However, wVulC, which interacts with aging, appears to be the prominent factor interfering with both PO activity and haemocyte density. This interference with immune parameters is not the only aspect of wVulC virulence on its host, as reproduction and survival are also altered.

Net biological oxygen production in the ocean—II: Remote in situ measurements of O 2 and N 2 in subarctic pacific surface waters

Net community biological production in the euphotic zone of the ocean fuels organic matter and oxygen export from the upper ocean, which has a large influence on the atmospheric pressure of carbon dioxide and is the driving force for metabolite distributions in the sea. We determine the net annual biological oxygen production in the mixed layer of the northeast subarctic Pacific Ocean from in situ O 2 and N 2 measurements. Temperature, salinity, total gas pressure and O 2 were measured every 3 h for 9 months in 2007 at about 3 m depth on a surface mooring at Station P (50°N, 145°W). The concentration of nitrogen gas, N 2, determined from separate total gas pressure and pO 2 measurements, was used as an inert tracer of the physical processes that induce gas departure from thermodynamic equilibrium with the atmosphere. We use a simple model of the ocean’s mixed layer along with the nitrogen concentration to constrain the importance of bubbles, gas exchange and horizontal advection, which are then used in the oxygen mass balance to derive net biological oxygen production. The mixed-layer oxygen mass balance is dominated by exchange with the atmosphere, and we determine a mean summertime oxygen production of 24 mmol O 2 m −2 d −1. The annual pattern in the difference between the supersaturation of oxygen and nitrogen in the surface waters reveals very little net oxygen production during the winter at this location. The calculated annual net community production (NCP) of carbon from this new method, 2.5 mol m −2 yr −1, agrees to within its error of about×40% with previous determinations at this location from oxygen mass balance, NO 3 − draw down and 234Th measurements. This value is either indistinguishable from or lower than annual NCP measurements in the subtropical North Pacific, indicating that there is no experimental evidence for differences in annual NCP between the subarctic and subtropical North Pacific Ocean.

Control of vertebrate skeletal mineralization by polyphosphates.

BackgroundSkeletons are formed in a wide variety of shapes, sizes, and compositions of organic and mineral components. Many invertebrate skeletons are constructed from carbonate or silicate minerals, whereas vertebrate skeletons are instead composed of a calcium phosphate mineral known as apatite. No one yet knows why the dynamic vertebrate skeleton, which is continually rebuilt, repaired, and resorbed during growth and normal remodeling, is composed of apatite. Nor is the control of bone and calcifying cartilage mineralization well understood, though it is thought to be associated with phosphate-cleaving proteins. Researchers have assumed that skeletal mineralization is also associated with non-crystalline, calcium- and phosphate-containing electron-dense granules that have been detected in vertebrate skeletal tissue prepared under non-aqueous conditions. Again, however, the role of these granules remains poorly understood. Here, we review bone and growth plate mineralization before showing that polymers of phosphate ions (polyphosphates: (PO3 −)n) are co-located with mineralizing cartilage and resorbing bone. We propose that the electron-dense granules contain polyphosphates, and explain how these polyphosphates may play an important role in apatite biomineralization.Principal Findings/MethodologyThe enzymatic formation (condensation) and destruction (hydrolytic degradation) of polyphosphates offers a simple mechanism for enzymatic control of phosphate accumulation and the relative saturation of apatite. Under circumstances in which apatite mineral formation is undesirable, such as within cartilage tissue or during bone resorption, the production of polyphosphates reduces the free orthophosphate (PO4 3−) concentration while permitting the accumulation of a high total PO4 3− concentration. Sequestering calcium into amorphous calcium polyphosphate complexes can reduce the concentration of free calcium. The resulting reduction of both free PO4 3− and free calcium lowers the relative apatite saturation, preventing formation of apatite crystals. Identified in situ within resorbing bone and mineralizing cartilage by the fluorescent reporter DAPI (4′,6-diamidino-2-phenylindole), polyphosphate formation prevents apatite crystal precipitation while accumulating high local concentrations of total calcium and phosphate. When mineralization is required, tissue non-specific alkaline phosphatase, an enzyme associated with skeletal and cartilage mineralization, cleaves orthophosphates from polyphosphates. The hydrolytic degradation of polyphosphates in the calcium-polyphosphate complex increases orthophosphate and calcium concentrations and thereby favors apatite mineral formation. The correlation of alkaline phosphatase with this process may be explained by the destruction of polyphosphates in calcifying cartilage and areas of bone formation.Conclusions/SignificanceWe hypothesize that polyphosphate formation and hydrolytic degradation constitute a simple mechanism for phosphate accumulation and enzymatic control of biological apatite saturation. This enzymatic control of calcified tissue mineralization may have permitted the development of a phosphate-based, mineralized endoskeleton that can be continually remodeled.

Fósforo orgânico em solos sob agrossistemas de cacau

A compreensão de parte do ciclo do P orgânico (Po) no solo poderá fornecer subsídios para o manejo eficiente da fertilização fosfatada no sistema de agricultura de baixos insumos na região tropical. O objetivo deste trabalho foi avaliar a variação de frações de Po em duas classes de solos sob diferentes agrossistemas de cacau no sul da Bahia. O Po total variou de 7,8 a 36,3 % do P total extraído, com teor médio de 193,3 mg kg-1. O teor médio de Po lábil foi de 15,2 mg kg-1, com variação de 33,1 a 81,9 % do P lábil total. Nos agrossistemas de cacau, o grupo de Latossolos apresentou menor teor de Po total, Po lábil e P microbiano do que o grupo de Cambissolos. No grupo de Latossolos, os solos sob agrossistemas de cacau apresentaram maior teor de Po total, P microbiano e P disponível, mas menor teor de Po lábil do que o solo sob floresta natural. O P disponível correlacionou-se positivamente com o Po (total, lábil e microbiano), e o Po total com o P microbiano. O Po lábil predominou amplamente sobre a fração inorgânica lábil, especialmente no grupo de Latossolos.

Formas de fósforo no solo sob leguminosas florestais, floresta secundária e pastagem no Norte Fluminense

Em solos muito intemperizados, a disponibilidade de P para as plantas está estreitamente associada às formas de P orgânico, que tem o seu conteúdo alterado por influência do tipo de cobertura vegetal. O objetivo deste trabalho foi estimar os teores de fósforo de compostos orgânicos (Po-total, Po lábil e P microbiano do solo), em plantios de Acacia auriculiformis (acácia) e Mimosa caesalpiniifolia (sabiá), em floresta secundária e em pastagem. Os teores médios ponderados de Po total e Po lábil, pelo teor de argila, foram de 375 mg kg-1 de P na argila e de 40,2 mg kg-1 de P na argila, respectivamente. Os solos sob acácia e sabiá apresentaram maior teor relativo de Po (total e lábil) do que os solos sob pastagem e capoeira. O Po representou de 22,6 a 39,6 % do P total extraído dos solos das coberturas estudadas. Em relação ao P lábil total, o Po lábil representou, em média, 67,1 %. Para o P microbiano, o maior teor foi encontrado no solo sob sabiá, seguido da floresta secundária, acácia e pastagem. Contudo, foi na capoeira que houve a maior eficiência da biomassa microbiana do solo em imobilizar P. O teor de P disponível por Mehlich-1 correlacionou-se positivamente com o teor de C e o de P da biomassa microbiana. Houve estreita correlação positiva entre o P microbiano e o C microbiano.

Secondary phase formation on UO2 in phosphate media

The dissolution of UO 2 (a chemical analog of uraninite and of spent nuclear fuel) has been studied by using a flow-through reactor. The UO 2 dissolution rates at total PO 4 3 - concentrations of 10 −4 , 10 −5 , and 10 −6 mol dm −3 have been determined to be: 1.3 × 10 −10 mol m −2 s −1 , 6.7 × 10 −11 mol m −2 s −1 , and 2.0 × 10 −11 mol m −2 s −1 , respectively. The dissolution rates determined are found to be higher than the ones determined for similar carbonate concentrations. Moreover, the surface of the UO 2 has been studied in static tests by means of the scanning force microscopy technique (SFM) in order to follow the formation of any secondary solid phase on its surface. The formation of chernikovite (H 2 (UO 2 ) 2 (PO 4 ) 2 · 8H 2 O) has been observed at a 10 −4 M total PO 4 3 - concentration, while no uranyl-phosphate secondary phases have been found at lower PO 4 3 - concentrations. In experiments performed in the presence of both carbonate and phosphate, no precipitation of secondary phases has been observed. It is postulated that this is due to the formation of the highly stable uranyl-carbonate complexes in solution.

Phospholipid synthesis rates in the eastern subtropical South Pacific Ocean

Abstract. Membrane lipid molecules are a major component of planktonic organisms and this is particularly true of the microbial picoplankton that dominate the open ocean; with their high surface-area to volume ratios, the synthesis of membrane lipids places a major demand on their overall cell metabolism. Specifically, the synthesis of cell membrane phospholipids creates a demand for the nutrient phosphorus, and we sought to refine our understanding of the role of phospholipids in the upper ocean phosphorus cycle. We measured the rates of phospholipid synthesis in a transect of the eastern subtropical South Pacific from Easter Island to Concepcion, Chile as part of the BIOSOPE program. Our approach combined standard phosphorus radiotracer incubations and lipid extraction methods. We found that phospholipid synthesis rates varied from less than 1 to greater than 200 pmol P L−1 h−1, and that phospholipid synthesis contributed between less than 5% to greater than 22% of the total PO43− incorporation rate. Changes in the percentage that phospholipid synthesis contributed to total PO43− uptake were strongly correlated with the ratio of primary production to bacterial production, which supported our hypothesis that heterotrophic bacteria were the primary agents of phospholipid synthesis. The spatial variation in phospholipid synthesis rates underscored the importance of heterotrophic bacteria in the phosphorus cycle of the eastern subtropical South Pacific, particularly the hyperoligotrophic South Pacific subtropical gyre.

Assessing nutrient limitation of Prochlorococcus in the North Pacific subtropical gyre by using an RNA capture method

It has been hypothesized that the planktonic community of the North Pacific subtropical gyre (NPSG) underwent a "domain shift" in the early 1980s in which phytoplankton of the domain Eukarya were supplanted by phytoplankton of the domain Bacteria, primarily Prochlorococcus. P limitation of eukaryotic phytoplankton was implicated as the causative chemical factor in the domain shift, and we sought to investigate the current nutrient limitation status of Prochlorococcus, now 2 decades since this event. We measured ribonucleic acid (RNA) synthesis rates by NPSG plankton at Station ALOHA in 33PO43‐ tracer incubations and found that RNA synthesis was the single largest biochemical sink for dissolved P, accounting for about half of the total PO43‐ uptake. We also found that NH4+ stimulated RNA synthesis but that PO43‐ did not, which suggested N limitation of plankton growth. We developed a new RNA capture procedure, termed radioisotope‐based tracking of RNA synthesis by hybridization and capture (RIBOTRACE), to measure RNA synthesis rates by Prochlorococcus exclusively. Data from this procedure showed that NH4+ stimulated RNA synthesis by Prochlorococcus and confirmed that Prochlorococcus was N limited and not P limited. Our RIBOTRACE data do not necessarily refute the domain shift hypothesis, but suggest that any critical period of P limitation required for the domain shift must have subsided and given way to the N‐limiting conditions that existed previously.

Fósforo orgânico em solos sob florestas montanas, pastagens e eucalipto no Norte Fluminense

Os solos tropicais muito intemperizados possuem, de modo geral, baixa disponibilidade de P para as plantas e elevada capacidade de adsorção de P inorgânico (Pi). Dessa forma, a manutenção de fontes orgânicas, capazes de suprir P por mineralização, é de grande importância para o crescimento de plantas em condições de acentuado intemperismo. A reciclagem de resíduos orgânicos e a habilidade da comunidade vegetal em conviver com baixas concentrações de P no solo garantem a sustentabilidade em ecossistemas naturais. O objetivo deste trabalho foi estimar o conteúdo de P orgânico (Po) total e as frações lábeis de P no solo, em duas florestas naturais (sítio 1 a 900 m de altitude e sítio 2 a 600 m), em um povoamento de Corymbia citriodora (sítio 3 a 250 m de altitude) e em pastagens adjacentes a cada cobertura florestal, em cada sítio. A taxa de recuperação de Pi + Po em relação à extração nitro-perclórica do P total variou de 50 a 82 %. O teor médio de Po total nos solos florestais foi de 160 mg kg-1 e, nos solos sob pastagem, de 69,8 mg kg-1. A maior diferença de Po total, entre floresta e pastagem, ocorreu no sítio 1 (-74 %), seguido do sítio 3 (-53 %) e sítio 2 (-25 %). O Po representou de 14,6 a 36,9 % do P total extraído. Em relação ao P lábil, o Po representou mais de 80 % nos solos sob florestas naturais e 65 % no solo sob eucalipto. O Po (total e lábil) correlacionou-se positivamente com o C orgânico, e o Po lábil com o P disponível.

Alteration of stream nutrient discharge with increased sedimentation due to thinning of a deciduous forest in Istanbul

The effects of 11% thinning on the nutrient outflux of a deciduous forest ecosystem in Belgrad forest is investigated with a paired watershed study. The treatment was a selective cutting to remove 11% of the standing volume uniformly throughout the watershed. Skidding was done by horse dragging and residues were left on site. Regression equations for selected water quality parameters were computed for calibration period (1980–1985) and calculated output values for the first year of post-treatment period was compared with observed ones. All linear regression equations were strong enough to be used in this procedure. Suspended sediment, total N, HCO 3 −, PO 4-P, Cl −, Ca 2+, Mg 2+, K + and Na + were the parameters in consideration. Most of them increased in the following winter months soon after precipitation reached to a considerable amount. Increase in suspended sediment, Cl −, Ca 2+, Mg 2+, and K + loads were statistically detectable ( p < 0.05) while total nitrogen and PO 4-P outputs remained almost unchanged after the treatment. Twenty percent, 23%, and 31% increases in annual suspended sediment, Cl −, and Ca 2+ discharges, respectively, due to a slight thinning treatment emphasize the importance of harvesting methods and techniques for nutrient cycling of a forest ecosystem.

The expansion and decline of charophyte communities in lakes within the Sejny Lake District (north-eastern Poland) and changes in water chemistry

Over the last 25 years, considerable changes have been observed in the littoral vegetation of 11 lakes within the Sejny Lake District. In eight lakes (Dowcień, Jurkowo, Kunis, Miałkie, Pilwie, Płaskie, Wiłkokuk, Zelwa) where Chara species dominated, their communities declined or disappeared completely. In four of these lakes (Dowcień, Jurkowo, Kunis and Miałkie), charophytes were replaced by communities of the class Potametea (mainly Nupharo-Nymphaeetum albae and Ceratophylletum demersi). In three other lakes (Pilwie, Płaskie and Wiłkokuk), the area covered by charophyte communities decreased. In Lake Zelwa, Charetum rudis and Charetum jubatae disappeared while Charetum tomentosae and Charetum fragilis expanded. A total area of charophyte communities remained approximately the same. A considerable increase in the water total hardness and PO 4 3 - concentration was noted in each of the eight lakes. In most of them increased levels of dissolved organic matter (measured as COD-KMnO 4) and pH were detected as well. However, the increase in the PO 4 3 - concentration was smaller in Lakes Wiłkokuk and Zelwa in which only slight changes in the vegetation were observed. In the above two lakes, the concentration of dissolved organic matter decreased and low water colour values are now noted. In three lakes (Długie, Dmitrowo and Gajlik), the charophyte communities tended to expand under the condition of moderate or high (Lake Długie) PO 4 3 - concentration, while dissolved organic matter concentrations were low. These lakes are also characterized by low values of colour. Charophyte communities may persist in lakes for a long period of time even when there is a moderate increase in PO 4 3 - concentration until the colour of water distinctly increases (>20 mg Pt L −1).

Production of the radicals in the ozonolysis of ethene: A chamber study by FT-IR and PERCA

The ozonolysis of ethene in dry synthetic air at atmospheric pressure and room temperature (298 ± 2) K was investigated in a 6065-L reaction chamber by in situ analysis of stable species by FTIR and of total peroxy radicals PO 2 (PO 2 = HO 2 + RO 2) by a chemical amplifier instrument. The yields of radical production were determined based on steady state concentrations of the peroxy radicals and the partitioning between HO 2 and RO 2 derived from model simulations. The radical yield is 0.38 ± 0.02 for HO 2 and 0.45 ± 0.03 for PO 2.

Sulfolipids dramatically decrease phosphorus demand by picocyanobacteria in oligotrophic marine environments

There is growing evidence that dissolved phosphorus can regulate planktonic production in the oceans' subtropical gyres, yet there is little quantitative information about the biochemical fate of phosphorus in planktonic communities. We observed in the North Pacific Subtropical Gyre (NPSG) that the synthesis of membrane lipids accounted for 18-28% of the phosphate (PO4(3-)) taken up by the total planktonic community. Paradoxically, Prochlorococcus, the cyanobacterium that dominates NPSG phytoplankton, primarily synthesizes sulfoquinovosyldiacylglycerol (SQDG), a lipid that contains sulfur and sugar instead of phosphate. In axenic cultures of Prochlorococcus, it was observed that <1% of the total PO4(3-) uptake was incorporated into membrane lipids. Liquid chromatography/mass spectrometry of planktonic lipids in the NPSG confirmed that SQDG was the dominant membrane lipid. Furthermore, the analyses of SQDG synthesis genes from the Sargasso Sea environmental genome showed that the use of sulfolipids in subtropical gyres was confined primarily to picocyanobacteria; no sequences related to known heterotrophic bacterial SQDG lineages were found. This biochemical adaptation by Prochlorococcus must be a significant benefit to these organisms, which compete against phospholipid-rich heterotrophic bacteria for PO4(3-). Thus, evolution of this "sulfur-for-phosphorus" strategy set the stage for the success of picocyanobacteria in oligotrophic environments and may have been a major event in Earth's early history when the relative availability of sulfate and PO4(3-) were significantly different from today's ocean.