Effect of Plant Growth Regulators on Calcium-stimulated Serine Transport into Tobacco Cells.

The transport of serine into tobacco cells (Nicotiana tabacum L.) cultured in liquid medium was examined. Transport was inhibited approximately 50% by 2,4-dichlorophenoxyacetic acid, indoleacetic acid, alpha-naphthalene acetic acid, and kinetin at a concentration of 10 micrograms per milliliter. Transport was not inhibited by 2,6-dichlorophenoxyacetic acid and inhibited less than 25% by p-chlorophenoxyacetic acid at this concentration. Removal of 2,4-dichlorophenoxyacetic acid from the transport medium resulted in an alleviation of inhibition. Gibberellic acid at concentrations from 2 to 20 micrograms per milliliter stimulated transport.It was previously shown that inhibition of transport by La(3+) was due to removal of Ca(2+) from surface sites and inhibition of Ca(2+) uptake by cells. None of the growth regulators tested had any significant effect on Ca(2+) binding and/or transport.A contributing factor to the low transport rates in the absence of Ca(2+) is the increased rate of serine efflux. None of the growth regulators tested had any significant effect on the rate of serine efflux.