Endogene rhythmik der produktionsfähigkeit bei Chlorella und ihre beeinflussung durch licht

Abstract

Summary 1. Autospores of Chlorella pyrenoidosa strain 211-8b (Algae Collection of the Institute of Plantphysiology, Gottingen) show characteristic changes in physiological activity during «waiting» under constant conditions in the dark which have been followed for 54 hours by measuring the production of dry-weight, carbohydrate, protein, chlorophyll and cellnumber in a testcycle (= light-dark-change 14 : 10 ¯ = LDC 14 : 10 ¯ ). 2. The changes in activity are endogenous and of a circadian nature (24 hrs. duration). The endogenous rhythm is independent of the developmental stage of the cells, appearing after both 14 : 10 ¯ , and 16 : 16 ¯ LDC as well as after culture in continuous light. 3. After continuous dim white light (about 20 lux) during «waiting» the rhythm could not be demonstrated; the physiological activity is at its minimum. 4. In the dim light the rhythm fades out in the individual cell. The transfer from dim light to continuous darkness restores the endogenous rhythm. This change serves as a stimulus for initiation of a rhythm (= Zeitgeber) in the individual cell and is not a synchronizing factor. 5. Also, when the dark period of the LDC is replaced by dim light the oscillator takes the phase of minimum production. This is one of the reasons why the productivity per light-hour in continuous light is not as high as under LDC. 6. The appearance of a maximum and minimum production in a testcycle after 0 and 12 hours of «waiting» respectively is due to the difference in the growthrate which occurs about 8 hours after the start of light. Similarly there are large differences in the rate of increase of protein and carbohydrate production at the 2nd and 4th hour after start of light depending on the duration of «waiting» received by the autospores. The carbohydrate production follows the pattern of endogenous rhythm.