Differences of Cu uptake and acid phosphatase activities of two Elsholtzia haichowensis Sun populations

Two Elsholtzia haichowensis Sun populations, one from Cu mine sites (Tonglushan) and the other from uncontaminated sites (Hongʹan) in Hubei Province, China, were investigated in hydroponic experiments for the differences of Cu accumulation and ecophysiological responses to Cu under Cu treatment. The results showed that a significant increase in malondialdehyde (MDA) concentration in roots was observed in Hongʹan population, whereas no significant change was observed in Tonglushan population. The root pressure exudates (ml) decreased significantly in Hongʹan population, but increased significantly in Tonglushan population at high Cu concentration (≥ 20 μ mol/L) treatment. Cu concentration in roots of Hongʹan population was significantly higher than that in Tonglushan population. For example, Cu concentration in Hongʹan population was 3 times and 4 times higher than that in Tonglushan population after 20 μ mol/L Cu treatment for one day and three days, respectively. Cu concentration in Hongʹan population was 20 times and 5 times higher than that in Tonglushan population after 80 μ mol/L Cu treatment for one day and three days, respectively. The intracellular and secreted acid phosphatase (APase) activities in roots were significantly higher in Tonglushan population than in Hongʹan one. The intracellular APase activities in Tonglushan population were 3 times higher than those in Hongʹan population after 80 μ mol/L Cu treatment for three days and five days, respectively. The root-secreted APase activities in Tonglushan population were 1.6 times and 1.8 times higher than those in Hongʹan population after 80 μ mol/L Cu treatment for three days and five days, respectively. In conclusion, excessive Cu caused serious oxidative damage in roots of Hongʹan population, but not in Tonglushan population. The high intracellular and root-excreted APase activities in Tonglushan population might play an important role in reducing Cu accumulation in roots and maintaining normal phosphorus physiological metabolism in root cells under Cu stress.