title: Evidence for a circaseptan and a circasemiseptan growth response to light/dark cycle shifts in nucleated and enucleated Acetabularia cells, respectively.
abstract: 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.
authors.forename: H G
authors.initials: HG
authors.lastname: Schweiger
authors.forename: S
authors.initials: S
authors.lastname: Berger
authors.forename: H
authors.initials: H
authors.lastname: Kretschmer
authors.forename: H
authors.initials: H
authors.lastname: Mörler
authors.forename: E
authors.initials: E
authors.lastname: Halberg
authors.forename: R B
authors.initials: RB
authors.lastname: Sothern
authors.forename: F
authors.initials: F
authors.lastname: Halberg
mesh_terms: D000076:Acetabularia / Q000254:growth & development*; D000460:Chlorophyta / Q000254:growth & development*; D003624:Darkness; D008027:Light; D010507:Periodicity