. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 446 I. WOODLAND HASTINGS AND BEATRICE M. SWEENEY BRIGHT LIGHT. 40 50 60 TIME-HOURS 100 FIGURE 5. This experiment illustrates a phase shift in the rhythm following changes in light intensity. Cells previously kept under LD conditions were placed at constant tempera- ture (° C.) and constant light intensity (100 foot-candles) at the end of a 12-hour dark period. Two days later (zero time on the graph) measurements of luminescence were begun and the endogenous rhythm was apparent. Some cultures (upper curve) were transferre
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 446 I. WOODLAND HASTINGS AND BEATRICE M. SWEENEY BRIGHT LIGHT. 40 50 60 TIME-HOURS 100 FIGURE 5. This experiment illustrates a phase shift in the rhythm following changes in light intensity. Cells previously kept under LD conditions were placed at constant tempera- ture (° C.) and constant light intensity (100 foot-candles) at the end of a 12-hour dark period. Two days later (zero time on the graph) measurements of luminescence were begun and the endogenous rhythm was apparent. Some cultures (upper curve) were transferred to bright light (1400 foot-candles) for a period of 6 hours and then returned to the previous condition (100 foot-candles). Other cultures (middle curve) were transferred to darkness for 6 hours and returned to dim light at 200 foot-candles. The time at which treatment was given is indicated by bars on the time axis. In both cases a marked phase shift in the rhythm is evident. The control (lower curve) was left in dim light all the while. Average period in control: hours. Figure 6 shows another technique which has been used in the study of phase shifting by single perturbations. Rhythmic cells were placed in the dark and, at a later time, received an exposure to light. Although the amplitude of the rhythm decreases over the next few days, the times at which maxima in lumines- cence occur are evident, so that the phase may be determined. The number of hours by which the phase is shifted would be expected to be some function of both the magnitude of the perturbation, and the time in the old cycle at which it is administered. The technique of interrupting darkness by light has been used to investigate these Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
