Aluminum precipitation, toxicity
Zea (aluminum and phosphate)
Springer Online Journal Archives 1860-2000
Abstract The effects of aluminum ions on the generation of mobile inorganic phosphate (Pi) within the cells of excised maize (Zea mays L.) root tips were examined using 31P-nuclear magnetic resonance (31P-NMR) spectroscopy. When perfused with a solution containing 50 mM glucose and 0.1–5.0 mM Ca2+ at pH 4.0, 3–5-mm-long excised maize root tips from 3-d-old seedlings showed a significant (approx. 100%) increase in the amount of mobile Pi, (primarily vacuolar) over a period of 30 h. This increase was above that which can be accounted for by the hydrolysis of endogenous sugar phosphates and nucleotides. A change of the pH of the perfusion solution to 7.0 reduced the increase in Pi to approx. 50%. Omission of Ca2+ in the solution at pH 4.0 caused the mobile Pi to increase to about 170%. However, the presence of Al3+ or both Ca2+ and Al3+ in the solution resulted in a significant loss (35–50%) of mostly vacuolar Pi over the same period of time. When root tips containing up to 65% of newly released Pi, produced after 20 h perfusion, were exposed to Al3+, no additional increase in the level of the mobile-Pi signal area was noted. Exposure to Al3+ with Ca2+ and glucose under hypoxia at pH 4.0 resulted in a threefold decrease in intracellular Pi content after the root tips were returned to aerobic conditions. These results indicate that external pH plays an important role in the generation of mobile intracellular Pi and that the presence of both Ca2+ and Al3+ can independently suppress the production of this excess Pi and ultimately reduce the vacuolar Pi.
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