Evidence for a circaseptan and a circasemiseptan growth response to light/dark cycle shifts in nucleated and enucleated Acetabularia cells, respectively.
Nucleated as well as enucleated Acetabularia mediterranea cells were subjected to 14 different patterns of shifts in a regimen of 12 hr of light alternating with 12 hr of darkness in four 30-day long experiments. With one exception, which might be due to a circannual modulation, these experiments showed that nucleated cells had maximal growth rates when a shift was performed every 7th or 15th day. In enucleated cells, maxima were observed on shift schedules that were about 3-4 days rather than about 7 days apart. The results indicate that in the unicellular green alga Acetabularia a rhythm of about 7 days (circaseptan) exists and that removal of the nucleus results in a circaseptan frequency multiplication.
Schweiger
H G
HG
Berger
S
S
Kretschmer
H
H
Mörler
H
H
Halberg
E
E
Sothern
R B
RB
Halberg
F
F
D000076:Acetabularia / Q000254:growth & development*; D000460:Chlorophyta / Q000254:growth & development*; D003624:Darkness; D008027:Light; D010507:Periodicity