Different patterns of organic acid exudation in metallophyte and agricultural plants at increasing copper levels

摘要

Copper (Cu) accumulation in shoot and root tissues and low molecular weight organic acids (LMWOA) root exudation have been studied in two metallophytes from Central Chile (Oenothera affinis and Imperata condensata) and two agricultural plants(Lupinusalbus and Helianthus annus) growing under hydroponics conditions at increasing Cu levels (0, 0.125, 0.250, 0.5, 1 and 2 mg Cu/L). The plants were grown in mineral solution for four weeks and after that in Cu-added solution for ten days, harvested and analyzed after this time. All the plant species showed high Cu accumulation, highlighting O. affinis with 116 and 2657 mg Cu/kg in shoots and roots, respectively. Strong differences in the LMWOA exudated by the different plant species were determined. O. affinis exudated high amounts of succinic acid, while 7. condensata exuded citric and oxalic acids. Acid root exudations from agricultural plants were mainly composed by citric acid. This result suggests that LMWOA root exudates by metallophytes play an important role against high Cu levels in polluted soils, being an important factor for plant selection in the design and implementation of phytoremediation programs.