JAPANESE KNOTWEED (REYNOUTRIA JAPONICA) AS A PHYTOREMEDIATOR OF HEAVY METALS

Abstract

Recently, plant remediation techniques-phytoremediation-have been developed. Japanese Knotweed (Reynoutria japonica), is an invasive species with negative impacts on the environment and the economy. In order to assess the tolerance of highly invasive weeds to heavy metals, an experiment was conducted in which this plant was grown in control soil and in soils contaminated with different concentrations of Pb, Cd. The content of heavy metals in the soil did not eliminate the ability of Reynoutria japonica roots to regenerate. In soil contaminated with any concentration of Pb, the shoots of this plant grew at a similar rate as the control plants, and had the same morphological characteristics. Higher concentrations of cadmium and lead Cd (100, 200 mg kg-1), Pb (2000 mg kg-1) have extended rhizome regeneration compared to control plants. In soils contaminated with lower concentrations of Cd or Pb shoots grew at a similar rate as control plants. Chemical analysis of heavy metal content showed that this weed accumulated large amounts of metals when grown in soil contaminated with heavy metals A relatively high intake of Cd, aboveground plants. At a cadmium concentration of 100 mg kg-1 , more than 537 times the amount of cadmium accumulated in the aboveground part of the plant, as opposed to that in control. The ability of Japanese Knotweed (Reynoutria japonica), to regenerate from parts of the rhizome, to grow and develop under stressful conditions in the presence of heavy metals indicates a high tolerance to heavy metals. INTRODUCTION Phytoremediation is a method that uses plants to remove or stabilize pollutants in the environment. The goal of remediation of contaminated areas due to human activity is to restore such ecosystems to their original state. Due to the application to a large number of pollutants, as well as the possibility of implementation on various surfaces, and due to lower environmental impact and lower costs, phytoremediation is considered a green technology. The toxicity of heavy metals in plants varies depending on plant species, metal specificity, metal content, its chemical form, soil composition and pH. Some metals, including Cu, Mg, Co, Zn, and Cr, are essential for plants in trace amounts, but only when metals are present in bioavailable forms, and in increased amounts can become toxic to plants (Nagajyoti, 2010). Mg, Co and Zn, have unknown biological functions and can cause disturbances even at relatively lower concentrations. Phytoremediation consists of four different technologies used by plants and each has a different mechanism for remediation of soils, sediments and waters contaminated with heavy metals. These include: