Flagellar photoresponses of Chlamydomonas cells held on micropipettes: II. Change in flagellar beat pattern

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Abstract
In response to step‐up as well as step‐down blue or white light stimuli, changes of beat pattern were observed in the two flagella of Chlamydomonas. The front amplitude was either increased or decreased, always in reverse in the two flagella. Again, two opposite combinations of step‐up and step‐down responses were found roughly in parallel to the two types of beat frequency changes. It is shown that positive phototaxis is probably achieved by the first type [called type (+)] and negative phototaxis by the second one [called type (−)]. Comparative measurements have revealed that frequency is not only related to the rate of flagellar movement, but also to the beat pattern. The rate of movement may change in different ways in the recovery and in the effective stroke. Though beat frequency and pattern changes are opposite in the two types, the rates of movement of the two flagella during the effective stroke are not always. In type (−) divergent changes were found in the rates of effective stroke movement, perhaps indicating the involvement of an additional mechanism.