Nutrient resorption patterns of plant functional groups in a tropical savanna: variation and functional significance

Green and senesced leaf nitrogen (N) and phosphorus (P) concentrations of different plant functional groups in savanna communities of Kruger National Park, South Africa were analyzed to determine if nutrient resorption was regulated by plant nutritional status and foliar N:P ratios. The N and P concentrations in green leaves and the N concentrations in senesced leaves differed significantly between the dominant plant functional groups in these savannas: fine-leaved trees, broad-leaved trees and grasses. However, all three functional groups reduced P to comparable and very low levels in senesced leaves, suggesting that P was tightly conserved in this tropical semi-arid savanna ecosystem. Across all functional groups, there was evidence for nutritional control of resorption in this system, with both N and P resorption efficiencies decreasing as green leaf nutrient concentrations increased. However, specific patterns of resorption and the functional relationships between nutrient concentrations in green and senesced leaves varied by nutrient and plant functional group. Functional relationships between N concentrations in green and senesced leaves were indistinguishable between the dominant groups, suggesting that variation in N resorption efficiency was largely the result of inter-life form differences in green leaf N concentrations. In contrast, observed differences in P resorption efficiencies between life forms appear to be the result of both differences in green leaf P concentrations as well as inherent differences between life forms in the fraction of green leaf P resorbed from senescing leaves. Our results indicate that foliar N:P ratios are poor predictors of resorption efficiency in this ecosystem, in contrast to N and P resorption proficiencies, which are more responsive to foliar N:P ratios.     

Supramolecular architectures constructed on the skeleton of Silver nitrate, 4,4′-bipyridine and triphenylphosphine/1,2-bis(diphenylphosphino)ethane: Synthesis, structural characterization and non-covalent interactions

In the presence of PPh₃ and Ph₂PCH₂CH₂PPh₂ (dppe); AgNO₃ and 4,4′-bipyridine (bpy) react to form [Ag(PPh₃)(bpy)_1/2(ONO₂)]_n (1) and [Ag(dppe)_1/2(bpy)_1/2(ONO₂)]_n (2). The compositions of these complexes are supported by their elemental analysis. The structures are determined by spectroscopic (IR, ¹H NMR, UV-Vis) and X-ray crystallographic data. A zig-zag ladder type structure observed in 1 changes into straight ladder type structure in 2 in which [Ag(dppe)_1/2(ONO₂)]_n chains are bridged by bpy with Ag?Ag distance of 11.48 Å. However in 1, the two zig-zag chains are linked via π-π interactions at 3.82 Å between phenyl rings of terminal PPh₃ ligands. Both complexes luminesce in DMSO solution. Photoluminescence of a representative complex 2 is also measured.     

Occurrence of Gluconacetobacter diazotrophicus in tropical and subtropical plants of Western Ghats, India

Endophytic bacteria were isolated from the tissues of surface sterilized roots, stems, and leaves of fifty different crop plants. Phenotypic, biochemical tests and species-specific PCR assay permitted identification of four isolates of Gluconacetobacter diazotrophicus from root tissues of carrot (Daucus carota L.), raddish (Raphanus sativus L.), beetroot (Beta vulgaris L.) and coffee (Coffea arabica L.). Further the plant growth promoting traits such as nitrogenase activity, production of phytohormone indole acetic acid (IAA), phosphorus and zinc solubilization were assessed. Significant nitrogenase activity was recorded among the isolates and all the isolates produced IAA in the presence of tryptophan. Though all the four isolates efficiently solubilized phosphorus, the zinc solubilizing ability differed among the isolates.     

Response of tomato (Lycopersicon esculentum Mill.) growth to different phosphorous levels and sowing dates

A field trail was carried out at the University of Agriculture Peshawar during spring, 2013 in order to evaluate the effect of different levels of phosphorus fertilizer and various planting times on the growth and development of tomato. The main objective of the research work was to investigate the best sowing time for tomato in combination with suitable dose of P fertilizer in order to get maximum yield of tomato in the climatic conditions of Peshawar. RCB Design with split plot arrangements was used in the trail. The main factor (phosphorous levels of 0, 90, 110, 130) was allotted to main plots while sowing dates in sub plots. A total twelve treatment were replicated thrice. Maximum days to flowering (39.583?days) and fruiting (46.167?days) obtained in the late sowing. Minimum days to flowering (39), minimum days to fruiting (38.778?days) were taken by the early sowing. Maximum number of branches (27.778), maximum fruit length (6.0222), maximum fruit with (6.1667), maximum fruit yield (24.653?tons?ha^?1) was produced when the plot fertilize with 130?kg?P?ha^?1. Maximum number of fruit?plant^?1 (29.778) were produced with application of 130?kg?P?ha^?1, minimum number of fruits (23.667?cm), fruit width (3.778?cm), fruit length (4.3667?cm), plant height (56.300?cm) were obtained from the controlled treatment. Among the various treatment studied in experiment, it is concluded that early planting of the tomato in the summer season i.e. in the start of March and the use of higher dose of P (130?kg?P?ha^?1) is very beneficial for the excellent growth, development and yield of tomato crop.     

Screening of biochemical parameters in the orthodontic treatment with the fixed appliances: A follow-up study

The aim of this study was to assess the changes in vital salivary parameters such as calcium, phosphorous, alkaline phosphatase, buffering capacity, pH, flow-rate and Oral Hygiene Index (OHI) in fixed orthodontic treatment patients during the retention period. In this study, saliva samples were collected from 35 patients before de-bonding (T₀) and after 4 to 5 weeks of de-bonding or on retention period (T₁). The biochemical parameters such as calcium, phosphorous and alkaline phosphatase levels were measured with saliva samples. Additionally, flow-rate, buffering capacity, pH and OHI levels was also measured. The current study results showed reduction in calcium, alkaline phosphatase, pH, flow-rate and OHI levels during T₁ (p < 0.05). However, phosphorous and buffering capacity levels were increased at T₁. The phosphorous levels showed non statistically significant difference when compared between T₀ and T₁ (p = 0.42). The remaining salivary parameters showed statistically significant difference when compared between T₀ and T₁ (p < 0.05). The present study concludes that there was a statistically significant decrease in the calcium, alkaline phosphatase, pH, flow rate and OHI values a month after de-bonding and increased in the buffering capacity values.     

抚仙湖窑泥沟人工湿地的除磷效果研究

为了减缓和控制抚仙湖局部湖湾水体富营养化趋势,在抚仙湖北岸建设了净化面积1 hm²的人工湿地.综合利用生物氧化塘、水平潜流人工湿地和表面流人工湿地治理技术,对入湖河道窑泥沟污水中磷的去除效果进行了试验研究.结果表明,该人工湿地系统对磷具有较强的去除能力.总磷去除率在57.7%～81.10%之间,平均去除率为54.9%.单位面积磷滞留量平均为26 mg·m^-2·d^-1,其中,湿地植物同化作用磷滞留量为26.1 mg·m^-2·d^-1,约占磷滞留总量的10%,大部分磷去除是通过基质吸附和沉降作用,但主要湿地植物水芹的季节变化对相应功能区的除磷效果会产生一定影响.试验期间,各功能区单位面积磷滞留量依次为水平潜流人工湿地＞生物氧化塘＞沉淀池＞表面流人工湿地.     

Phosphorous pentoxide mediated synthesis of 5-HMF in ionic liquid at low temperature

A convenient, mild and environment-friendly dehydration reaction of fructose in ionic liquid using phosphorous pentoxide (P₂O₅) has been investigated. The acidic nature of P₂O₅ along with its hygroscopic properties has been successfully utilized to afford 81.2% yield of 5-hydroxymethylfurfural (5-HMF) at 50 °C in 60 mins. Phosphoric acid yielded remarkably less 5-HMF even at higher temperature and longer reaction times. The reaction was optimized by varying different parameters and the results indicated that no rehydration products, such as levulinic acid or formic acid, were formed.     

Influences of travertine dam formation on leaf litter decomposition and algal accrual

At the time of this study Fossil Creek was being considered as a site for the restoration of a native fish assemblage, however there was concern amongst fisheries managers about the stream being food limited due to calcium carbonate (travertine) deposition. To evaluate the effects of travertine deposition on the aquatic food base we used leaf litterbags to compare decomposition rates and nutrient diffusing artificial substrates to compare algal accrual rates and nutrient limitation between two distinct reaches in Fossil creek: a travertine dam forming reach and a reach without travertine dam formation (riffle-pool reach). Decomposition was significantly faster in the travertine dam forming reach than in the riffle-pool reach. Macroinvertebrates in the leaf packs were more diverse in the travertine reach but more abundant in the riffle-pool reach. Algae accrued more quickly in the travertine reach than in the riffle-pool reach and only responded to nutrient enrichment in the travertine reach. This study was conducted prior to a hydroelectric dam decommissioning project in Fossil Creek where full flows were reintroduced back into the stream after a century of diversion. Our results suggest concurrent increases in algal productivity, decomposition, and macroinvertebrate diversity in the next decade as travertine dams rebuild, providing a richer food base for fish and other aquatic organisms. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. Handling editor: K. Martens     

Changes in soil phosphorus fractions in a calcareous paddy soil under intensive rice cropping

We conducted a 4-year field experiment on a calcareous paddy soil in Zhejiang province of China to measure the changes in chemically extracted soil P fractions in an irrigated double-cropping rice system. Treatments included four fertilizer combinations (unfertilized control, NK, NP, and NPK) as main-plots and two rice cultivar types (inbred vs. hybrid rice) as sub-plots. Total plant P uptake and grain yield of rice declined in all treatments over time. Severe P-deficiency and significant rice yield losses began in treatments without P application after the second rice crop. Compared to inbred rice, hybrid rice increased grain yield (+18%), N uptake (+11%) and K uptake (+27%) but there was no significant difference in total plant P uptake. Recovery efficiencies of fertilizer-P averaged 31–32% in both cultivars. In treatments without P application, the P mass balance was negative (−6 to −8 kg P ha⁻¹ crop⁻¹) and phosphorus was drawn down in all inorganic P fractions, including resin, alkali- (NaHCO₃-Pi and NaOH-Pi) and acid-soluble P fractions (dilute HCl-P, concentrated HCl-P, residual-P). Only small amounts were removed from organic P fractions, 1–3 mg P kg⁻¹ year⁻¹ from NaHCO₃-Po and none from NaOH-Po. In treatments with fertilizer-P addition, the P mass balance was positive (+8 to 10 kg P ha⁻¹ crop⁻¹), soil P declined at a slower rate in inorganic P fractions and it increased (+51%) in the residual-P fraction. Hybrid rice generally caused greater depletion of inorganic soil P fractions than inbred rice, but there was no difference among cultivars in their effect on NaHCO₃-Po and NaOH-Po. Positive correlations (r = 0.63–0.81, P < 0.001) were observed between all inorganic P fractions (except residual-P) and total P uptake by rice. Our results suggest that rice plants draw P from a continuum of chemically extracted fractions that are assumed to have widely differing plant P availability. Regular P additions are required to maintain the effective soil P supply and differences between inbred and hybrid rice should be taken into account in P management strategies.     

Effect of ferrous sulphate on nitrification during simultaneous phosphorus removal from domestic wastewater using a laboratory scale anoxic/oxic reactor

In the present study a laboratory scale anoxic/oxic reactor was used to remove the important eutrophication nutrients such as phosphorus and nitrogen from synthetic domestic wastewater. Phosphorus was removed through simultaneous precipitation and was carried out using the coagulant ferrous sulphate FeSO₄ · 7H₂O. Total phosphorus in the effluent was controlled to below 1 mg/l using a ferrous to phosphorus molar ratio of 2.1. pH after the addition of coagulant plays a major role in determining the molar ratio of the precipitant. Nitrogen was removed biologically in the anoxic/oxic system and the effect of simultaneous precipitation on nitrification and denitrification was investigated. The nitrification rate of the system remained unaffected during simultaneous precipitation and varied from 0.046 to 0.059 g N–NH₄ ⁺/g VSS/day. Denitrification was complete and was not affected by the coagulation process. The nitrogen removal efficiency varied from 78% to 85%. COD removal efficiency was not affected during simultaneous precipitation and was varied from 94% to 98%. The highly efficient nitrogen removal in the presence of simultaneous precipitant ferrous sulphate makes the process an ideal option for nutrient removal.