Mechanism of Radioactive Zinc Uptake by Ulva Lactuca1

The effects of metabolism, pH, carrier ions, and temperature upon the uptake and accumulation of Zn65 by Ulva lactuca from sea water in light and dark were investigated. The pattern of uptake in relation to light and temperature in unbuffered sea water was what would be expected assuming zinc absorption to be a metabolic accumulation process proportional to the rate of photosynthesis as has been previously reported. However, uptake rate and the level of accumulation was found to be strongly pH dependent and to be affected by the concentration of zinc in the media. Freshly killed Ulva absorbed more tracer than live material. These findings suggest that the physical process of adsorption or cation exchange is primarily responsible for Zn66 uptake. The relationship between photosynthesis and zinc absorption is primarily a secondary effect related to surface/volume ratio and pH.