Influence of 2,4-Dichlorophenoxyacetic Acid on Solute Uptake by Chlorella.

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Abstract
Cells of Chlorella pyrenoidosa suspended in phosphate buffer at pH 5.5 containing concentrations of 2,4-D ranging from 10-7 to 10-2 [image] undergo pronounced alterations in permeability to some solute molecules. Solutes which exist entirely or in part as uncharged particles are markedly affected by the auxin, while no change in the uptake of ions due to 2,4-D was observed in these studies. Under conditions which minimize metabolic use of sucrose-C-14 and mannitol-C14, low concentrations of 2,4-D cause an increase in the uptake of these solutes, while an increase in 2,4-D concentration results in a progressive decrease in the amount of these materials entering the cells. Uptake of P3204 by Chlorella is increased more by low 2,4-D concentrations than is that of the carbohydrates, while increased concentrations have less inhibitory effect on phosphate uptake. Uptake of S3504 and Na22Cl by Chlorella was not affected by 2,4-D under the conditions used for permeability studies, although in an environment favorable for metabolic activity the uptake of these solutes is altered by 2,4-D. The decrease in cell permeability in the presence of high 2,4-D concentrations was not due to the death of the cells. Information is given on relative rates of uptake for these solutes under different temperature conditions.