ISSN:
1432-136X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Rhythmic cultures ofGonyaulax polyedra Stein (Strain 70) were placed in constant dim light and analyzed for ultrastructural changes over a period of 32 h. Circadian changes were observed in chloroplast shape and distribution within the cell, as measured quantitatively by the percentage of chloroplasts covering the surface area of the cell, the length of the chloroplasts and their penetration into a central area which is occupied by chloroplasts at only one time of day. Chloroplast portions penetrated this area during the entire subjective day but not during the subjective night. Chloroplasts within this region showed expanded interlamellar distances, whereas only slight changes in the interlamellar distances were observed in the other portions (nearer to the periphery of the cell) of the chloroplast. No changes were observed in the intralamellar distances over the course of a day. In addition, circadian rhythms were detected in the percentage of two and three-stacked thylakoid lamellae and in the number of starch granules present in a defined inner and outer region of the cell. Few if any changes could be observed in the measured diameters of the tubular cristae or in the distances between outer and inner membranes of the mitochondria. Exposure to 1 μM cycloheximide for one hour did not immediately affect the ultrastructural parameters measured or other structural features of the cell. However, such pulses phase-shifted the measured rhythms by 8 to 12 h, the amount being dependent on the circadian phase at which the pulses occurred.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00688729
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