A rapid method of determining growth characteristics of plant cell populations in batch suspension culture

A non-destructive, simple and accurate method of determining the relative growth rate (RGR) of the packed cell volume (PCV) of plant suspension cells in one Erlenmeyer flask at any time during the incubation period is described. The Erlenmeyer flask was tilted and the length of the chord formed by the surface of the packed cells across the bottom of the flask was measured. The chord length and the log PCV were correlated in a calibration line. The method enables the RGR during the exponential growth phase to be calculated by multiplying the slope of the linear part of the curve of the chord length in time with the slope of the calibration line. In order to investigate other growth parameters and to analyse the accuracy of the method statistically, a four-parameter function for the chord length and a computer program were used. The RGR during the exponential growth phase of cell suspensions of Solanum tuberosum and Haplopappus gracilis appeared to be independent of the PCV of the inoculum. The method appeared to be sufficiently accurate.     

Manifestations of vitamin D deficiency in chicks reared under different artificial lighting regimes

A problem observed with zoo animals that normally do not consume vitamin D-containing foods and that are not exposed to natural sunlight is a deficiency of vitamin D. This study was conducted to determine whether the amount of ultraviolet light emitted by certain commercially available lights is sufficient to promote vitamin D₃ synthesis as indicated by weight gain and various measures of skeletal calcification. Seventy-four, day-old male leghorn chicks were randomly assigned to six treatment groups for a 6-week trial. All groups were exposed to a cool white fluorescent light. In addition, group 1 was supplemented with 400 IU of vitamin D₃/kg diet, group 2 was supplemented with 100 IU of vitamin D₃/kg diet, group 3 served as the negative control, group 4 was exposed to a Vita-Lite for 12 hr per day, group 5 was exposed to a Sylvania sun lamp for 15 min twice daily, and group 6 was exposed to a Sylvania black light for 15 min twice daily. Groups 3 through 6 were not provided with dietary supplements of vitamin D₃. At termination of the experiment, groups 1, 2, and 5 all showed healthy beaks and ribs, the highest weight gain, and greatest percentage of bone ash. Group 4, in contrast, had the poorest calcification and lowest bone ash. This finding indicates that supplemental artificial lighting does affect vitamin D₃synthesis in chicks and presumably in other species but that certain lights that were presumed to be appropriate for this purpose proved to be unsuitable under the conditions of this study.     

Responses of ring widths and maximum densities of Larix gmelinii to climate on contrasting north- and south-facing slopes in central Siberia

An analysis was performed of the climatic responses of the radial growth of Larix gmelinii (Rupr.) Rupr. at two sites—both of which included contrasting north- and south-facing slopes—in Tura, central Siberia, with the development of ring width and maximum-density chronologies for each slope. Both residual and standard chronologies of ring widths were positively correlated with temperature from late May until mid June on all four slopes. By contrast, standard chronologies of ring widths were negatively correlated with precipitation during the winter (from October to April) and in May on the north-facing slope at site 1 and on the south-facing slope at site 2 respectively. The negative correlations with precipitation during the winter and in May on some of the slopes suggested that delayed snowmelt in early spring might inhibit the radial growth of L. gmelinii, and the effects of snow are likely to vary with topography. Both residual and standard chronologies of maximum densities were positively correlated with temperature in early July on all four slopes. Maximum densities were also positively correlated with precipitation during summer of the previous year on all the slopes. These suggest that no major differences exist in terms of responses of maximum density to climatic factors between the north- and south-facing slopes.