Formation of mixed invasions of waterfowl

It is established that wild and synanthropic waterfowl of the order Anseriformes (gadwell, mallard, graylag goose, teal, garganey, etc.) are possible sources of mixed invasions i.e., an etiological factor in forming and maintaining ill-being of domestic geese with respect to the following diseases: echinostomatidosis, amidostomosis, ganguleterikidosis, thominxosis, streptocarosis, echinuriosis, as well as ectoparasites (bird lice).     

Observation of polymer conformation hysteresis in extensional flow

Highly extensible Escherichia coli DNA molecules in planar extensional flow were visualized in dilute solution by fluorescence microscopy. For a narrow range of flow strengths, the molecules were found in either a coiled or highly extended conformation, depending on the deformation history of the polymer. This conformation hysteresis persists for many polymer relaxation times and is due to conformation-dependent hydrodynamic forces. Polymer conformational free-energy landscapes were calculated from computer simulations and show two free-energy minima for flow strengths near the coil-stretch transition. Hysteresis cycles may directly influence bulk-solution stresses and the development of stress-strain relations for dilute polymer flows.     

A RAPID STAINING METHOD FOR RICKETTSIA ORIENTALIS

A rapid method for staining R. orientalis is described. Smears of infected tissues are defatted and stained in a dilute aqueous solution of methylene blue and basic fuchsin. Smears thus stained show R. orientalis as blue organisms on a pinkish-purple background.     

Effects of delay in reapplication of nitrogen fertilizer following cutting silage from a ryegrass sward

Plots of a 2-year-old sward of Merlinda perennial ryegrass received a routine dressing of 100 kg N ha⁻¹ as compound fertilizer in March 1991, followed by further dressings of 100 kg N ha⁻¹ after cuts 1, 2 and 3 in a simulated four-cut silage system, either the same day as cutting or with a delay of 3, 7, 10 or 14 d. Partial irrigation ensured that fertilizer could be taken up immediately. Annual total dry matter yield, the dry matter yield for the experimental cuts 2–4 and their apparent response to N showed no effect of delays of 0–10 d in reapplication of fertilizer, but a significant ( P < 0·01) reduction for 14 d delay. Significantly ( P = 0·001) higher apparent recovery of N in the cut herbage was recorded where reapplication of fertilizer had been delayed by 7 or 10 d (93% and 91% respectively) in comparison with either smaller (0 delay, 78%; 3 d delay, 87%) or greater delay (14 d, 86%). It is suggested that lower recoveries at 0 and 3 d result from the sward's reduced NO₃ uptake following defoliation and that, while in practical situations the conditions may not be as rigorous as those imposed in this experiment, further experiments to determine the fate of N not recovered in the herbage are warranted, so defining management circumstances in which immediate reapplication of N might not be advisable.     

Studies on the Physiology of Hyacinth Bulbs Hyacinthus Orientalis L. I. Sugar Content and Metabolic Activities in Bulbs Exposed to Low Temperatures

Changes in the content of carbohydrates and in the activity of hydrolytic enzymes were studied in hyacinth bulbs exposed to low temperatures. It was found that the amount of insoluble carbohydrate initially present in the scales and buds of hyacinth bulbs decreased greatly after a prolonged period of low temperature treatment. This decrease was greater in rooted bulbs, held at a low temperature for 63 days in natural conditions, than in unrooted bulbs stored in a refrigerator for the same period. At the same time the levels of soluble mono- and oligosaccharides, and of soluble starch, increased in the scales and buds of chilled bulbs. These changes in sugar level were found to be correlated with changes in the activity of certain hydrolytic enzymes. The activity of these enzymes was higher in rooted bulbs than in those which had not rooted before treatment. The activity of hydrolytic enzymes was found to be considerably higher in the flower buds than in the scales.