The effect of the herbicide 2,4,5 trichlorophenoxy acetic acid (245T) on the growth and metabolism of Tetrahymena pyriformis.

The herbicide 2,4,5 trichlorophenoxy acetic acid (245T) at concentrations from 0.5 to 0.9 mM, was found to inhibit respiration and then growth in exponentially growing cultures of Tetrahymena pyriformis. Cell division was stopped for periods up to 60 minutes after which the cells recovered and division resumed. Recovery of oxygen utilization and cell division occurred in the presence of 245T. 245T was shown to inhibit mitochondrial oxygen utilization. Mitochondria from cells that had recovered from 245T treatment lost their sensitivity to low concentrations of the herbicide and sedimented deeper in a sucrose gradient than mitochondria from control cells.