Growth, root and leaf structure, and biomass allocation in Leucanthemum vulgare Lam. (Asteraceae) as influenced by heavy-metal-containing slag

Abstract

Effects of heavy metal contamination on growth, leaf turnover, biomass allocation and leaf and root structure of Leucanthemum vulgare Lam. were investigated. Plants were grown in two outdoor experiments, for 5 weeks or for 3 months, respectively, on sand with different additions of slag containing elevated levels of heavy metals, especially Cu and Ni. In the 3-month experiment nutrients were provided as composted manure, in the 5-week experiment as a solution. Slag contamination reduced plant growth, biomass allocation to roots, specific root length and specific leaf area, while root tissue density and leaf dry matter content increased. Fine root diameter increased, whereas coarse root diameters showed a non-significant decreasing trend. Toxicity of slag was lower in the 3-month experiment, probably due to organic matter in the substrate. We conclude that heavy metals in the soil around Cu–Ni smelters may, besides directly reducing growth of the plants, increase their susceptibility to other stresses such as drought, by reducing the root length to leaf area ratio. Fine and coarse roots show distinct responses, indicating that different root diameter classes should be regarded separately to fully understand stress responses of root systems.