Synchronization of the desmidStaurastrum gracile

Summary Cultures ofStaurastrum gracile maintained in a liquid medium in a 168 hours light: dark regime were asynchronous. Alteration of the regime to 1410 or 186 failed to induce synchrony, as did variation of the light and dark temperatures. The cultures were synchronized by eliminating a light period to give a total dark period of 32 hours. One such cycle gave 54% synchrony, the cells entering division at the onset of the second light period after treatment. The omission of a second light period 72 hours after the first produced no increase in the level of synchrony. The level was improved by omitting a further light period 48 hours after the first to give a 321632 induction treatment which resulted in 64% synchrony. In no instance did the cells divide between the dark treatment and the synchronized wave of cytokinesis. The mechanism of this synchrony may be explained by the existence of an essential, dark-labile division precursor.This work forms part of a thesis submitted byRoy Rowley to the University of Manchester for the degree of M.Sc.