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| Titel: |
When Does Subjective Day Come Under 24-h Light/Dark Cycles?: The Case of Circadian Rhythms of UV-C Resistance and Timing of Cell Division in Euglena gracilis |
| Auteur: |
C.K. Beneragama K. Goto |
| Verschenen in: |
International journal of botany |
| Paginering: | Jaargang 6 (2010) nr. 1 pagina's 28-34 |
| Jaar: |
2010 |
| Inhoud: |
Circadian rhythms are generally believed to help organisms to adapt to the environments that fluctuate daily. To achieve this adaptation, they should entrain to the external cycles and establish a stable phase-relationship between internal and external cycles. However, no consensus has been obtained as to when each internal phase comes under the entrainment to 24 h Light/Dark (LD) cycles with various day-lengths. In the flagellated alga Euglena gracilis Z grown photoautotrophically, we report here that subjective (or internal) dawn, noon and dusk in the circadian rhythms of UV-C resistance comes exactly at the external dawn, noon and dusk, respectively, regardless of the day-lengths under 24-h LD cycles; circadian rhythm of the timing of cell division reveals consistent phase behavior. We conclude therefore that the entire subjective day (dawn to dusk) may exactly match the external day. Since, the circadian phototaxis rhythm in this alga behaves differently, we also suggest that the alga possesses at least two circadian clocks per cell that respond differently to external cycles. We moreover discuss about the fact that our conclusion may contradict the widely-held view that circadian clocks stop and stay at subjective dusk just after day-lengths exceed 12 h under 24 h LD cycles. |
| Uitgever: |
Asian Network for Scientific Information (provided by DOAJ) |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
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