This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Heide, O. M. Articles by Evans, L. T. Search for Related Content PubMed PubMed Citation Articles by Heide, O. M. Articles by Evans, L. T. Agricola Articles by Heide, O. M. Articles by Evans, L. T.

Articles

A Semidian Rhythm in the Flowering Response of Pharbitis nil to Far-Red Light

I. Phasing in Relation to the Light-Off Signal

CSIRO Division of Plant Industry, G.P.O. Box 1600, Canberra, ACT 2601 Australia

Evidence is presented of an endogenous rhythm in flowering response to far-red (FR) irradiation, with a period of about 12 h (hence semidian rhythm), which persists through at least three cycles in constant conditions of continuous light at 27°C and has a marked influence on the flowering response in Pharbitis nil to a subsequent inductive dark period. The phase of the rhythm is not influenced by real time nor by the time from imbibition or from the beginning of the light period. Rather, it is fed forward from the beginning of the FR interruption to the beginning of the inductive dark period. The period of the rhythm is not affected by irradiance but is longer at cooler temperature. When there are two FR interruptions during the preceding light period, it is primarily the later one which determines the phase of the rhythm, although some interactions are evident. There appears to be an abrupt rephasing of the rhythm at the beginning of the inductive dark period. No overt rhythms which could be used as "clock hands" for the semidian rhythm were detected in photosynthesis, stomatal opening, or translocation.