Treating seed with Bacillus cereus strain UW85 stimulates nodulation in soybean, but the underlying mechanisms of this stimulation are poorly understood. In this study we assessed the effects of inoculation on nodulation, nitrogenase activity and dry matter partitioning in soybean (cv. Maple Ridge), common bean (cv. OAC Rico) and pea (cv. Express) under controlled, gnotobiotic conditions. Plants were grown for 34 d under controlled-environment conditions without a mineral N source, at low two levels of (brady)rhizobia inoculation. Soybean and common bean were grown at a single temperature regime and pea was grown at two temperature regimes. Each trial consisted of five treatments (noninoculated control, low (brady)rhizobia inoculation, low (brady)rhizobia plus UW85 inoculation, high (brady)rhizobia inoculation, and high (brady)rhizobia plus UW85 inoculation) with six plants as replicates per treatment in a completely randomized design. Inoculation of soybean with UW85 increased growth of roots, shoots, and nodules across both levels of bradyrhizobia inoculation and increased plant N accumulation by 12%. In oculation with UW85 also increased whole-plant nodulation (nodules plant-1) by 16%, but there were no effects on specific nodulation [nodules g-1 root dry weight (DW)], individual nodule DW, nitrogenase activity (μmol H2 g-1 nodule DW h-1) or N2 fixation efficiency (g plant-N g-1 nodule DW). Inoculation of pea with UW85 at the low temperature regime increased whole-plant nodulation by 19%, but had no positive effects on any other growth parameters. Inoculation of common bean with UW85 had no positive effects on any aspects of growth, nodulation or nitrogenase activity. Our data indicate that under gnotobiotic conditions, UW85 inoculation increases nodulation in soybean indirectly by increasing root growth and not stimulating the nodulation process per se. The bacterium had little to no positive effects on pea and common bean symbioses. Key words: Bacillus cereus UW85, Glycine max, growth-promotion, nodulation, Phaseolus vulgaris, Pisum sativum

Bacillus cereus UW85 inoculation effects on growth, nodulation, and N accumulation in grain legumes: Field studies. Can. J. Plant Sci. 82: 291-298. Bacillus cereus strain UW85 was assessed for growth-promotion effects on soybean and common bean in the presence and absence of rhizobial inoculation at two field sites in Manitoba in 1994. Growth promotions due to B. cereus UW85 occurred for soybean only, and only at one site. Promotions in plant emergence in soybean were apparent at 60 d after planting (DAP), but stimulations in shoot dry weight (DW), N concentration, and N content were not apparent until 90 DAP. At maturity (120 DAP), inoculation with UW85 resulted in stimulation of seed yield by 9% and seed N content by 14%. However, stimulation in growth and N parameters by UW85 treatment was proportionally greater in the absence of B. japonicum inoculation than in the presence of the rhizobial inoculant. These observations, in combination with the observations that nitrogenase activity was not stimulated by UW85 treatment, clearly indicate that the UW85-mediated stimulation of growth and N accumulation of soybean is via a generalized stimulation of plant growth, and not via a stimulation in the soybean-B. japonicum symbiosis per se. Overall, our study indicates that inoculation with UW85 has the potential of increasing soybean production in western Canada, but these effects are site specific and are not seen in common bean. Incidence de l'inoculation de Bacillus cereus UW85 sur la croissance, la nodulation et l'accumulation de N chez les légumineuses à graine: Études sur le terrain. Can. J. Plant Sci. 82: 291-298. Les auteurs ont essayé de déterminer les effets de la souche UW85 de Bacillus cereus sur la croissance du soja et du haricot commun, avec et sans inoculation de rhizobium. Les essais se sont déroulés à deux endroits, au Manitoba, en 1994. B. cereus UW85 n'a accéléré la croissance que du soja, à un seul site. La levée plus importante des plants était manifeste 60 jours après la plantation, mais la hausse du poids sec des pousses, de la concentration de N et de la teneur en N des graines n'est apparue qu'au bout de 90 jours. À maturité (120 jours après la plantation), l'inoculation de UW85 avait augmenté le rendement grainier de 9 % et la teneur des semences en N de 14 %. La stimulation de la croissance et les paramètres associés à l'azote étaient néanmoins proportionnellement plus importants sans inoculation de B. japonicum qu'avec cet inoculant. Ces observations et celle que l'administration de UW85 n'accroît pas l'activité de la nitrogénase indiquent clairement que la stimulation de la croissance et l'accumulation de N observées chez le soja après le traitement résultent d'une accélération générale de la croissance et pas d'une meilleure symbiose entre B. japonicum et le soja comme telle. Dans l'ensemble, l'étude révèle que l'inoculation de UW85 pourrait accroître la production de soja dans l'ouest du Canada, avec la réserve que de tels effets sont spécifiques au site et ne se reproduisent pas chez l...

The purpose of this study was to determine if multiple experimenters would have any effect on the preferences of mallard ducklings for broods of 3, 6, or 9 ducklings. Three different experimenters ran 2 different subjects each day for 7 consecutive days. The mean age of the subjects was 24 h at the onset of testing. The dependent variable was the amount of time each subject spent with a brood of 3, 6, or 9 ducklings during a Ifi-min trial. It was found that a brood of 9 ducklings was preferred significantly more often (p < .05) than a brood of 6 or a brood of 3 ducklings. The results also indicated that with the task described and the ages involved, different experimenters did not contribute significant sources of variation to the results obtained.Developmental research involving avian species can potentially consume large amounts of one experimenter's time and energy. The use of multiple experimenters can ease the burden that would be placed upon one experimenter in terms of the time and the energy required for a particular study .The Avian Behaviour Laboratory in the Department of Psychology at the University of Manitoba is interested in those mechanisms that mediate an attachment between parents and their young, between young and their parents, and among the young. For mallard ducklings (Anas platyrhynchos platyrhynchos) and giant Canada goose goslings (Branta canadensis maxima), the developmental period of interest to us is the first 7 days of the young bird's life. Shapiro (1977) stated that the formation of an attachment is a continous phenomenon and does not end when a subject reaches 24 or 36 h of age .Over a 7-day testing period , an experimenter is subject to many possible disruptions. The experimenter may become ill, grow tired, be injured, have a death in the family, or be subject to an array of unexpected and unanticipated events.The use of multiple experimenters would minimize the problems caused by such disruptions. Over a 7-day testing period, two or three trained experimenters can divide the time required by the experiment equally among themselves. If one experimenter becomes subject to an unforeseen event, another experimenter can replace the stricken experimenter and continue the research that may have taken months to prepare. The avian literature illustrates the formation of research teams that ranged in size from two experimenters (Kertzman & Demarest, 1982; Taylor & Sluckin , 1964) to four experimenters (Taylor, Sluckin, Hewitt, & Guiton, 1967) 1977). These experiments, however, do not state whether one or more than one experimenter ran the subjects and, if the latter, whether there was an experimenter effect.The use of multiple experimenters introduces a new source of variability to the study under investigation. The possible effects of multiple experimenters and the possibility of an interaction between this variable and other independent variables being used in the experiment must be evaluated. The purpose of this article is to examine the possible effects of multiple experimenters ...