Date of issue: 
Circadian clock is one of the most fascinating adaptations to life on Earth. Thanks to the internal clock organisms can not only respond to the periodic succession of day and night, but also measure the length of day, which is an indicator of the seasons. Endogenous clock generates rhythms of approximately 24 hours . Setting the clock is done mainly through changes in temperature and light conditions at dawn and dusk. The mechanism responsible for the generation of circadian rhythms consists of three main components: the entrance road of environmental factors synchronizing operation of the clock , the internal oscillator , way out in the form of rhythmic physiological and developmental processes controlled by the clock . Light is an essential signal biasing the clock . It has been shown a close relationship between the photoreceptors and the components of the biological clock in different research models . In plants, two families of molecules photoreceptor phytochrome and cryptochromes i.e. , are involved in the transduction of light signal to the oscillator . ZTL family of proteins , FKF1 and LKP2 ( containing the LOV domain , kelch repeat motif and cassette F -box ) and newly identified nuclear proteins GI and ELF3 also involved in the transmission of the light signal to the clock . Molecular studies on the internal oscillator in different organisms (eg Arabidopsis thaliana , Neurospora crassa , Drosophila melanogaster ) suggest that it functions as a feedback loop consisting of positive and negative elements . The proteins encoded by the genes function as the clock negative elements which inhibit its own expression by blocking of transcription factors , which are elements of the positive . In plants, most likely oscillator elements are: TOC1 protein or APRR1 ? component of the two-component regulatory system responses ( called response regulator ) protein and two transcription factors MYB domain equipped - LHY and CCA1 . It has been shown that the plant circadian clock controls a large variety of physiological and developmental processes of plants include cell growth , stomatal opening movements of leaves and flowering.
Author of the article: 

The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

Editorial address:
Katedra i Zakład Histologii i Embriologii Uniwersytetu Medycznego w Poznaniu, ul. Święcickiego 6, 60-781 Poznań, tel. +48 61 8546453, fax. +48 61 8546440, email:

PBK Postępby biologi komórki