Cu and nutrient deficiency on different effects of growth, tolerance and mineral elements accumulation between two Elsholtzia haichouensis populations

Two Elsholtzia haichowensis populations, one from a copper mine (CS) and the other from an uncontaminated site (UCS), were studied in hydroponic experiments for the plant growth, copper accumulation and mineral nutrients content under excess copper, nutrient deficiency and their interaction. The growth of UCS population was significantly inhibited by excessive Cu, nutrient deficiency and their interaction. But the growth of CS population was less affected by these factors, and 25 mu mol/L Cu stimulated significantly the growth of CS population. The tolerance indices of root length to Cu and biomass to mineral nutrient deficiency in the CS population were significantly higher than that in the UCS population. The results indicated that the CS population had evolved not only Cu tolerance but also tolerance to low nutrient supply. Nutrient deficiency increased significantly Cu uptake and transport in two populations. For example, at 25 mu mol/L Cu mixed with nutrient deficiency, root-Cu content of CS population was about 25 times that of CS population at 25 mu mol/L Cu treatment; root-Cu content of UCS population at interaction of 25 mu mol/L Cu and nutrient deficiency was more than 5 times that of CS population at 25 mu mol/L Cu treatment. Shoot-Cu contents in two populations also increased, but that in UCS population increased much more than in CS population. Excessive Cu reduced significantly uptake and transport of mineral nutrient including P, Mg, K and Mn. But contents of these mineral elements in CS population was less affected by excessive Cu. At interaction of nutrient deficiency and Cu (25 mu mol/L), mineral element contents except Ca and some Fe decreased significantly. But the reduction in CS population is less than that in UCS population. The results indicated that the mineral composition homeostasis under the stresses was important in metal tolerance and colonizing normally in the Cu-enriched soils for the Cu-tolerant population.