PH DEPENDENT ALUMINUM TOXICITY TO NOSTOC-LINCKIA - STUDIES ON PHOSPHATE-UPTAKE, ALKALINE AND ACID-PHOSPHATASE-ACTIVITY, ATP CONTENT, PHOTOSYNTHESIS AND CARBON FIXATION

Al toxicity to Nostoc linckia was enhanced by changing the pH from 7.5 to 4.5. The ATP content and the physiological processes studied were highly affected by a combination of Al and low pH. Although the rate of inhibition of ATP was slow in Al treated cells, it was slower in cells treated with high Al dose and low pH. PS I and redox coupling between the two photosystems depicted more susceptibility to Al than PS II. Electron transport was completely stopped at pHs 6 and 4.5 combined with 0.8 mM and 0.6 Al, respectively. These results suggest that Al disrupts the ATP synthesis at high pH but binds with ATP at acidic pH, thus making it metabolically unavailable.