Hormone effects on Cosmarium botrytis cell division

The synchronous generation time for Cosmarium botrytis Menegh. was 48 h at pH 8.0, and 72 h at pH 5.3. Cells divided 2 to 3 prior to the end of the dark phase in a 15 h light/9 h dark cycle at 21 degrees C. Kinetin at concentrations of 0.01 to 1.0 mg/ml, added to cells at the beginning of the light cycle, eliminated the initial lag phase at both pH 5.3 and pH 8.0, and all cells divided until 24 h. Indole-acetic acid in concentrations of 0.03 to 0.06 mg/ml decreased the lag phase to less than 48 h at pH 5.3, and eliminated the lag phase at pH 8.0. Normal generation time was re-established in 6 to 12 days. Daily addition of identical amounts of both IAA and kinetin maintained the 24 h division cycle up to 14 days. Kinetin was lethal at 3 mg/ml and IAA at 0.05 mg/ml. IAA and kinetin in combinations of previously effective and non-effective concentrations did not have synergistic or additive effects. Cell numbers did not correlate with optical density at 678 nm. Medium pH dropped in steps coinciding with cell division.