Assessment of differences in anatomical and hydraulic properties of the root and xylem of three willow (Salix L.) clones during phytostabilization after exposure to elevated cadmium

An anatomical study of adventitious roots of three Salix clones, B-44, SV068 and SM4041, treated with 3 and 6 mg Cd kg-1 dry weight in soil in a greenhouse experiment. The aim was to analyze the anatomical characteristics of roots in response to pollution by cadmium and to assess the potential application of anatomical and hydraulic characteristics in the selection of the most suitable Salix clones for phytostabilization of pollutants in soils. Anatomical parameters measured in this study included root crosssectional area, root diameter, the proportion of periderm, secondary phloem (cortex) and wood (secondary and primary xylem), and parameters of the vessels (lumen area, diameter and frequency). Based on the measurements of individual vessel lumens and the number of vessels, the theoretical hydraulic conductivity (kh) of roots was calculated. The effects of applied Cd concentrations on root traits were studied in clones and control plants. Following treatments with both Cd concentrations, plants of clone B-44 had the highest values of most parameters and significantly higher kh in comparison with control samples due to the significantly larger root cross-sectional area and lumen of vessels. It was concluded that these characteristics can serve for effective evaluation and selection of clones for remediation of sites contaminated with cadmium.