. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. H I FIGURE 4. Experimental designs for determination of action spectra. Black indicates dark period; shaded, experimental monochromatic light; open, white light; A, hypothetical short day, no response; B, hypothetical long day, full response; C, action spectrum determined with a monochromatic long day in conjunction with a short night; D, action spectrum deter- mined with both dawn and dusk extentions of a white-light short day; E, action spectrum determined with a monochromatic "night" and a white-light short day;
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. H I FIGURE 4. Experimental designs for determination of action spectra. Black indicates dark period; shaded, experimental monochromatic light; open, white light; A, hypothetical short day, no response; B, hypothetical long day, full response; C, action spectrum determined with a monochromatic long day in conjunction with a short night; D, action spectrum deter- mined with both dawn and dusk extentions of a white-light short day; E, action spectrum determined with a monochromatic "night" and a white-light short day; F, G, action spectra determined with monochromatic extentions of a white-light short day into long day in the dusk and dawn, respectively; H, I, action spectra determined with monochromatic light breaks at the sensitive period early and late in the subjective night, respectively. portant implication is that both the critical photoperiod and the number of days required for the termination of diapause are decreasing during the winter and early spring. At the same time, environmental daylengths are rapidly increasing. The net result is to endow the intrinsic accuracy of the photoperiodic clock with increased precision. Consequently, the transition from diapause-maintaining to diapause-terminating daylengths should take place more rapidly under natural con- ditions than is implied by response to static daylengths in the laboratory. Given a photoperiodic system, there are many ways to set up an energy- compensated action spectrum (Fig. 4). Each of these methods has its own limita- tions. If one assumes that a short-day response is evoked by a regimen such as 4A and a long-day response by 413, then an action spectrum could be determined by substituting monochromatic light for white light (4C ). for dark (4E), or by adding short bursts of monochromatic light to both ends of a white-light, short-day regimen (4D). These three methods have the drawback that they only assay for wavelengt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
