Changes on organic acid secretion and accumulation in Plantago almogravensis Franco and Plantago algarbiensis Samp. under aluminum stress

We investigated the effect of Al (400 μM) on organic acids secretion, accumulation and metabolism in Plantago almogravensis Franco and Plantago algarbiensis Samp. Al induced a significant reduction on root elongation only in P. algarbiensis. Both species accumulated considerable amounts of Al (>120 μg g−1) in their tissues, roots exhibiting the highest contents (>900 μg g−1). Al stimulated malonic acid secretion in P. algarbiensis, while citric, succinic and malic acids were secreted by P. almogravensis. Moreover, Al uptake was accompanied by substantial increases of citric, oxalic, malonic and fumaric acids contents in the plantlets of either species. Overall, the acid metabolizing enzymes were not directly involved in the Al induced organic acid secretion and accumulation. Our data suggest that Al detoxification in P. almogravensis implies both secretion of organic acids from roots and tolerance to high Al tissue concentrations, while in P. algarbiensis only the tolerance mechanism seems to be involved.

► Both Plantago species accumulate considerable and similar amounts of Al.
► Al induced a significant reduction on root elongation only in P. algarbiensis.
► Organic acids secretion in P. almogravensis was stimulated by Al.
► Al uptake was accompanied by increases of organic acids contents in both species.