[Investigation of the light dependence of the uptake of rubidium, zinc, cobalt, lead and cerium by Chlorella by a flow method]

Abstract

A flow method for the measurement of the uptake of labelled substances by plant cells has been developed. Accumulation in the medium of substances released by the plants is thereby avoided, and a more precise determination of the rate of uptake-also of transients-than through the usual, static methods is possible. The time function of the stimulation of the uptake of Rb by Chlorella fusca by light at 30° has been analyzed, and the component believed to represent active transport separated from other components that have shorter time constants; at 3° the active component is much reduced.In the cases of the heavy metal ions Zn, Co, Pb and Ce, even after presaturation with the ions in the dark for the suppression of the short-term uptake the light-independent long-term uptake is far stronger than with Rb. Moreover, for Zn and Co the uptake is greatly stimulated by light at 30°, but little if at all at 5°. No stimulation was found under any conditions with Ce. With Pb, the light effect was hardly reproducible, and in any case extremely small. The energy-dependent transport of Zn and Co is probably active.