. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 442 12 J. WOODLAND HASTINGS AND BEATRICE M. SWEENEY. 20 ~AO 60 80 TIME- HOURS 10O 120 145 FIGURE 1. The effect of light intensity upon the natural period at constant temperature (21° C.)- The cells were grown in LD conditions (800 foot-candles during the light period). The beginning of the experiment, shown on the graph as 0 time, fell at the end of a normal light period. At this time, some cells were placed in the dark, and others in light of 120 foot- candles (upper curve), 380 foot-candles (middle) and 680 foot-candles (b
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 442 12 J. WOODLAND HASTINGS AND BEATRICE M. SWEENEY. 20 ~AO 60 80 TIME- HOURS 10O 120 145 FIGURE 1. The effect of light intensity upon the natural period at constant temperature (21° C.)- The cells were grown in LD conditions (800 foot-candles during the light period). The beginning of the experiment, shown on the graph as 0 time, fell at the end of a normal light period. At this time, some cells were placed in the dark, and others in light of 120 foot- candles (upper curve), 380 foot-candles (middle) and 680 foot-candles (bottom). The average periods were as follows: 680 foot-candles, hours; 380 foot-candles, hours; 120 foot- candles, hours; dark, hours (not shown on graph; one period measured). In view of the relatively small temperature effect, the period of this rhythm may be characterized as essentially temperature-independent. The endogenous nature of the diurnal rhythm. The persistence of the rhythm of luminescence under conditions of constant temperature and light intensity indi- cates that the mechanism of the rhythmicity is endogenous. Several other experi- ments serve to support this conclusion. Figure 2 illustrates one of many experiments in which the phase of the rhythm was shifted by changing the time at which the light and dark periods occurred. In such experiments the phase (, the solar time at which the maximum in luminescence occurs) may be shifted so that it will bear any desired relationship to the solar day. In cultures which are subsequently transferred to constant con- ditions of dim light or darkness, the phase of the persistent rhythm is related to the previous light and dark program rather than to solar time, or any other factor. Changes in the phase of the endogenous rhythm have not been observed when light and temperatures were held Please note that these images are extracted from scanned page images that may have been digitally enhan
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
