Interactive effects of aluminum, phosphorus and mycorrhizae on growth and nutrient uptake of Panicum virgatum L. (Poaceae)

The effects of Al on Panicum virgatum (switchgrass), a widespread perennial grass, were determined in relation to factors which might interact with Al in the soil. Plants were grown for 8 weeks in sand culture and were treated with 3 Al levels (0.5, 2.0, 5.0 mM), 2 P levels (0.065, 0.161 mM), 2 inoculum types (vesicular-arbuscular mycorrhizal (VAM) inoculum or VAM-free soil inoculum) and 2 inoculum sources (a high Al forest in NY or a low Al forest in Ohio) in a factorial design. Plant growth decreased with increasing Al and increased with increasing P, but the Al effect was less at high P than low P. VAM-inoculated plants outgrew non-VAM plants, especially at low and medium Al levels. Total P and Ca uptake decreased with increasing Al concentration, especially at low P levels. VAM inoculation did not result in increased P uptake at any Al level though VAM plants took up significantly more Ca than non-VAM plants at any Al level. VAM plants had lower tissue Al concentrations and took up less Al than non-VAM plants; Al uptake increased with increasing soil Al in non-VAM plants but not in VAM plants. Plants given inoculum from the high Al site had significantly lower tissue Al than plants given the low Al site inoculum, regardless of VAM status. We conclude that the presence of a VAM infection, moderate levels of soil P, and the source of the inoculum can reduce the effects of soluble Al. We discuss potential physiological and edaphic mechanisms by which Al may be immobilized and Ca availability increased in the presence of VAM fungi and other soil microflora.     

Predictors of intentions to leave the ward,the hospital,and the nursing profession: A longitudinal study

The stages preceding and following the intention to withdraw from an organization have not been adequately examined. Data were collected at two time periods from a sample of 146 nurses working in a general hospital located in a large metropolitan area in Israel. Essentially, intention to withdraw from three levels — ward, hospital and profession — were examined. LISREL was used to test alternative longitudinal models for the best fitting set of linkages among variables. The findings supported a progression model of withdrawal intention. According to this conceptualization, a nurse first decides to leave the ward, then the hospital, and, finally, the profession. Theoretical and practical implications of the results were presented.     

Organizational attitudes and behaviors as a function of participation in strategic and tactical change decisions: An application of path–goal theory

Based upon path–goal theory of leadership, decision type (strategic versus tactical) was suggested as a moderator variable between employee participation in decision making (PDM) and work outcomes. A total of 249 respondents in five Israeli organizations undergoing planned changes, participated in the study. Results from four out of the five organizations revealed that participation in tactical rather than strategic decisions was a better predictor of an increase in change acceptance, work satisfaction, effectiveness, and time allotted to work. The stronger effects associated with tactics rather than strategy were found even if PDM expectations were included. Theoretical and practical implications of the results were discussed.     

Vetiver (Vetiveria zizanioides) responses to fertilization and salinity under irrigation conditions

Vetiver (Vetiveria zizanioides) has not been widely introduced in arid and semi-arid regions where irrigation, fertilization, and salinity are important factors in plant growth. The main objective of this study was to determine the response of vetiver to fertilization (fertigation) and salinity and their interactions under irrigated conditions. The experiment was conducted in a greenhouse in 10-L pots. Combined effects of three nutrients concentrations and three salinity levels of electrical conductivity (EC) 1, 3 and 6 dS/m in the irrigation water on growth and transpiration of vetiver plants and the content of different elements in their foliage were studied. Similar contents of 3.7 g/kg Na, 5.77 g/kg Ca and 2.55 g/kg Mg were found in the foliage of all the plants irrigated with the different fertilizer and salinity levels. Concentrations of 59 mg/L N and 36.1 mg/L K in the irrigation water were sufficient for vetiver plants needs at the different salinity levels tested. The salinity threshold (the maximum EC in the soil solution that does not cause a significant yield reduction) for vetiver was between 3 and 6 dS/m. A concentration of 15.2 mg/L P in the irrigation water was the optimum value for vetiver growth in the three salinity levels, resulting in an average content of 5.95 g/kg P in plant foliage. It is suggested that vetiver is sensitive to excess P (>8.66 g/kg). Increasing EC in the irrigation water to 6 dS/m decreased plant foliage biomass mainly due to an increase in the osmotic potential of the irrigation water and high Cl⁻ concentration in the foliage.     

On the efficacy of credibility intervals as indicators of moderator effects in meta-analytic research

Researchers have suggested the use of credibility intervals for identifying moderator effects in meta-analysis. In the present study, the accuracy of decisions derived from credibility intervals was determined from Monte Carlo generated correlations based on two series of meta-analyses, one containing 20 studies and the other, 100 studies. Within each study, the responses of 100 subjects were simulated. Although in some marginal cases the accuracy measures (Type I error rate and power) from the credibility intervals were better than those derived from the SH-75 per cent and U rules, the former technique was generally found to be a poor indicator of heterogeneity or homogeneity. Finally, the concept of a large interval was discussed and a rule of thumb for using it to detect moderators was suggested.