Phosphate as a control factor in cell division of Chlamydomonas reinhardti, studied in synchronous culture

Abstract

Growth, cell division and time course of accumulation of macromolecules has been compared in Chlamydomonas reinhardti during synchronized vegetative growth in complete and phosphate free medium. Deprivation of P i from the growth medium at the beginning of the life cycle (zoospore stage) led to 1. 1. shortening of G1 phase with earlier start of DNA synthesis, karyokinesis, cytokinesis and sporulation (with reduction in spore number). 2. 2. Moderate variation in protein content and oscillation of RNA content. 3. 3. Decrease in degree of synchrony of nuclear division and sporulation. 4. 4. Derepression of phosphatases. Re-addition of P i at different times to cells grown in P-free medium from the beginning of the life cycle, demonstrated a transition period in the cells regarding the processes started by the removal of P i .