Copper Phytoextraction in Tandem with Oilseed Production Using Commercial Cultivars and Mutant Lines of Sunflower

Abstract

Use of sunflower (Helianthus annuus L.) for Cu phytoextraction and oilseed production on Cu-contaminated topsoils was investigated in a field trial at a former wood preservation site. Six commercial cultivars and two mutant lines were cultivated in plots with and without the addition of compost (5% w/w) and dolomitic limestone (0.2% w/w). Total soil Cu ranged from 163 to 1170 mg kg−1. In soil solutions, Cu concentration varied between 0.16– 0.93 mg L−1. The amendment increased soil pH, reduced Cu exposure and promoted sunflower growth. Stem length, shoot and capitulum biomasses, seed yield, and shoot and leaf Cu concentrations were measured. At low total soil Cu, shoot Cu mineralomass was higher in commercial cultivars, i.e., Salut, Energic, and Countri, whereas competition and shading affected morphological traits of mutants. Based on shoot yield (7 Mg DW ha−1) and Cu concentration, the highest removal was 59 g Cu ha−1. At high total soil Cu, shoot Cu mineralomass peaked for mutants (e.g., 52 g Cu ha−1 for Mutant 1 line) and cultivars Energic and Countri. Energic seed yield (3.9 Mg air-DW ha−1) would be sufficient to produce oil. Phenotype traits and shoot Cu removal depended on sunflower types and Cu exposure.