Effects of aluminum on organic acid metabolism and secretion by red spruce cell suspension cultures and the reversal of Al effects on growth and polyamine metabolism by exogenous organic acids

In the absence of added Al, the concentration of succinate in cultured red spruce (Picea rubens Sarg.) cells was 15-20 times higher (> 600 nmol g-1FW) than that of citrate or oxalate and 4-6 times higher than that of malate. Addition of AlCl3 (effective monomeric Al concentrations of 0.23 and 0.48 mM) to 3-day-old suspension cultures significantly increased cellular succinate concentrations with a concomitant decrease in cellular oxalate concentrations. However, in the medium of Al-treated cell cultures, both succinate and oxalate concentrations were significantly higher than in the medium of cell cultures without added Al, and oxalate concentrations were several times higher than succinate concentrations. Aluminum did not significantly affect the cellular concentrations of malate, ascorbate and citrate, and none of these organic acids was present in detectable quantities in the medium. Exogenous succinate alone or with Al had no effect on cellular free polyamine concentrations or cell mass. Aluminum caused a significant increase in cellular putrescine concentrations. Addition of malate had a positive effect on growth and completely reversed the effects of Al on cell physiology. In contrast, the addition of oxalate and citrate only partly reversed the effects of Al.