عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Background and Objectives
Environmental pollution is the result of industrial societies and industrialization of human society. Copper is an essential micronutrient for plants growth and development when the copper concentration in the water is high, as one of the most toxic heavy metals for living organisms. Some plants are known as copper accumulator. Watercress (Nasturtium officinale) is an aquatic plant species from Brassicaceae family. Greenhouse experiments have showed that watercress has high accumulation ability of some heavy metals.
Material and methods
This study aimed to examine the effects of copper on growth and physiological characteristics of Nasturtium officinale. Accordingly, effects of different levels of copper sulfate (0, 4, 8, 12, 16 µM)
in N. officinale in a complete randomized design with three replications were studied. Rooted cuttings of N. officinale were transferred to hydroponic culture, in 1-L polyethylene pots containing a modified half-strength Hoagland’s solution. Nutrient solutions were renewed weekly and plants were grown in a growth chamber (20/15 °C day/night; light intensity 200 µE m-2 s-1, 16 h day-1; relative humidity 75 %). After 14 days of pre-culture, plants were exposed to different levels of copper sulfate. The plants were harvested for analysis after having grown in the test solution for 2 weeks.
The results showed that in the 4 µM copper treatment, fresh and dry weight of shoots, shoot length, leaf area and RWC increased, but at higher concentrations (8, 12, 16 µM) these characteristics significantly decreased. The root and shoot copper concentrations consistently increased with increasing copper exposure. At the 16 µM of copper in the nutrient solution, the average of copper concentrations in root and shoot was 4210 and 558 µg/g d.w., respectively. According to the results, shoot copper concentration was lower than the root and very little of that was transferred into the shoot.
In total, according to the results, copper sulfate significantly decreases the shoots and roots of fresh and dry weight as well as root length, shoot length and leaf area, and increases the total chlorophyll, but no significant effect on the amount of Protein, Carbohydrate, Anthocyanin and Carotenoid. Generally, the threshold of this plant is to 4 µM copper.