Mann+Hummel, Germany

Abstract

To better understand the unique concentration–response relationship in hyperaccumulators, the effects of manganese (Mn) accumulation on the growth of Celosia argentea Linn., a Mn hyperaccumulator, were investigated using hydroponic experiments. Manganese accumulation (8860–14200 mg/kg in leaves) is toxic to most plants but beneficial to the growth of C. argentea. The C. argentea root length and root surface area at Mn supply concentrations of 20 and 40 mg/L were significantly higher than those at 0.5 mg/L (control treatment). Leaf number and leaf area were 24 % and 66 % greater, respectively, at 20 mg Mn/L than at the control concentration. Moderate Mn accumulation (8860–14200 mg/kg) significantly increased plant dry weight (p < 0.05). However, high Mn accumulation (26,500 mg/kg) decreased plant dry weight. The chlorophyll content expressed a similar trend. The physiological responses of C. argentea to Mn may be regulated by endogenous hormones. Moderate Mn accumulation increased auxin, zeatin, gibberellin, and 6-benzylaminopurine contents, and decreased the abscisic acid content in the leaves (p < 0.05), thereby enhancing plant growth. However, high Mn accumulation significantly increased leaf jasmonic acid and abscisic acid contents (p < 0.05), which inhibited plant growth and stimulated stress tolerance. These findings suggested that the alterations in hormone homeostasis induced by Mn accumulation promoted growth and Mn tolerance in C. argentea.