| Abstrakt: |
The rate of uptake, the effects of carrier ions, temperature, light intensity and dinitrophenol (DNP) upon the uptake of zinc (using zinc-65 as tracer) by Fontinalis antipyretica were investigated. The absorption medium contained 0.5 mM CaSO4 and the pH was kept constant using boric acid and sodium hydroxide as buffer. About 50 per cent of the zinc absorbed at equilibrium was taken up in the first half hour. Analysis by semi-log plot procedures showed that, at least, three sections may be distinguished in the uptake curve, suggesting that three successive processes (stages) were involved. The first stage was very short, and not influenced by temperature, light intensity and DNP. The second stage, lasting no more than 90 minutes, was very slightly affected by the same three factors. In this stage freshly killed plants absorb more zinc than living material. The third stage, lasting several days, was very slow and was light, temperature and DNP dependent. Based on these findings, a mechanism for zinc uptake is proposed. [ABSTRACT FROM AUTHOR] |
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