Effect of Aluminum on the Uptake and Metabolism of Phosphorus by Barley Seedlings

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Abstract
The rate at which P was accumulated by Al-treated roots was much faster than in controls, especially during initial stages of uptake. The extra P was all Pi and was almost completely exchangeable. Similar rapid accumulation of Pi was found in Al-treated roots in the presence of 10-3 M dinitrophenol and at low temperature. Al treatment decreased incorporation of P32 into sugar phosphates but increased the pool size of adenosine, uridine, and guanine triphosphates. Specific activity of P32 in adenosine tri-phosphate was similar in controls and Al treatments. In vitro tests showed that aluminum citrate inhibits purified yeast hexokinase activity. Results suggest at least 2 sites for Al/P interactions: (1) at cell surface resulting in fixation of P by an adsorption-precipitation reaction; and (2) in mitochondria resulting in decrease in sugar phosphorylation by inhibition of hexokinase.