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Aims Global change may cause unparalleled supplies of soil nutrients and further lead to stoichiometric imbalance of nitrogen (N) and phosphorus (P) in terrestrial plants. While previous studies had reported the effects of global change factors on plant N, P contents and their ratios, few had examined whether or how these factors may influence the scaling of these two elements. Methods Taking advantage of a manipulative experiment with altered precipitation, warming and N addition, and using the general scaling function N = βP α , we examined how the scaling of plant N to P may respond to global change factors in a Loess grassland in northwestern China. Important Findings We found that precipitation reduction (PR) and warming decreased plant P concentrations, while N addition increased plant N concentrations, resulting in increased N:P ratios. The slopes of the linear regressions between plant N and P (i.e. log-transformed N versus P) did not change significantly, whereas the intercepts increased significantly under PR, warming and N addition. These results indicate that global change factors may not affect the synergistic variation of plant N and P, showing a closely coupled relationship between them. Our findings may help to better understand plant nutrient dynamics and element balance in a changing world. [ABSTRACT FROM AUTHOR]

Background and aims: Nitrogen (N) deposition greatly influences ecosystem processes through the alteration of plant nutrition; however, there is limited understanding about the effects of phosphorus (P) inputs, especially within the backdrop of N deposition. Methods: Here we investigated the plant stoichiometric responses to P addition under both ambient conditions and with N addition in a temperate grassland in Inner Mongolia over a two-year period. Results: The effects of P addition on foliar nutrition and stoichiometric ratios were highly dependent on the presence of N supply, in that P addition showed no significant impacts on foliar N or P concentrations (or pools in community biomass) or N:P under ambient N conditions, but enhanced foliar N in dominant species and foliar P in almost all species (and pools in community biomass) with N addition. These results may be explained by P addition significantly changing the soil properties (soil pH and available P) when applied in combination with N additions. Moreover, there was no biomass response to nutrient additions. Conclusions: Our results suggest that N deposition may enhance the absorption of additional P by plants in semi-arid grasslands, and that P limitation with increased N deposition might be less important for limiting plant growth than previously anticipated. [ABSTRACT FROM AUTHOR]

Plant carbon : nitrogen : phosphorus (C:N:P) ratios are powerful indicators of diverse ecological processes. During plant development and growth, plant C:N:P stoichiometry responds to environmental conditions and physiological constraints. However, variations caused by effects of sampling (i.e. sampling date, leaf age and root size) often have been neglected in previous studies. We investigated the relative contributions of sampling date, leaf age, root size and species identity to stoichiometric flexibility in a field mesocosm study and a natural grassland in Inner Mongolia. We found that sampling date, leaf age, root size and species identity all significantly affected C:N:P stoichiometry both in the pot study as well as in the field. Overall, C:N and C:P ratios increased significantly over time and with increasing leaf age and root size, while the dynamics of N:P ratios depended on species identity. Our results suggest that attempts to synthesize C:N:P stoichiometry data across studies that span regional to global scales and include many species need to better account for temporal variation. [ABSTRACT FROM AUTHOR]

The inclusion complex of β-cyclodextrin with gossypol was synthesized by using a convenient method of microwave irradiation. The structure of the complex was determined by 1H NMR, IR spectroscopy, and as well as the elemental analysis; the thermal stability was studied by means of differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The association constant between gossypol and β-cyclodextrin measured via UV spectroscopy was 4462 M−1 at room temperature, following stoichiometry 1:2. [Copyright &y& Elsevier]

Abstract: Features of the inclusion complex between gossypol (Gos) and β-cyclodextrin (CD), such as its aqueous solubility, association constant, characteristics in the solid state and crystalline morphology, as well as the stoichiometry of this complex have been determined. The phase–solubility diagram drawn using UV detections belongs to an AN-type. Fluorescence detection and calculation with the modified Benesi–Hidebrond equation provide an 1:2 stoichiometry for the complex. Its apparent stability constant has been determined to be 3203M−1 by fluorescence technique and confirmed by the calculation from UV spectroscopy. X-ray powder diffractions (XRD) and Scanning Electron Microscopy (SEM) observations showed a clear difference in the crystal morphology of the complex from those of both Gos and β-CD. [Copyright &y& Elsevier]