Differences in structure of adventitious roots in Salix clones with contrasting characteristics of cadmium accumulation and sensitivity

Lux, A.; Šottníková, A.; Opatrná, Jana; Greger, M.
PHYSIOLOGIA PLANTARUM 120 [4]: 537-545, 2004

Abstrakt: Various clones of Salix spp. have contrasting characteristics of accumulation, translocation to shoots and of sensitivity to cadmium (Cd). The aim was to investigate the structure of adventitious roots and find out if differences between groups of clones in root anatomy accounted for differences in relation to Cd. Stem cuttings of eight clones of Salix spp. with different combinations of high or low Cd accumulation, translocation of Cd to shoots and sensitivity to Cd, were cultivated for 3 weeks in hydroponics containing 100 µM Ca(NO3)2. No Cd was added in this experiment. Equal-sized roots were selected for hand-sectioning and fluorescence staining to detect the beginning of Casparian band formation and suberin lamellae deposition in endodermis. In addition, root apices were fixed, embedded, sectioned longitudinally and transversally, and stained. The image analysis system LUCIA was used for quantitative evaluation of tissue differences. The structure of adventitious root apices showed an intermediate-open type of root apical meristem and the clones differed in organization of root apices. Clones with low accumulation of Cd and high Cd tolerance had smaller meristematic zones and more extensive vacuolation of cells in the root apices than clones characterized by high accumulation of, and high sensitivity to, Cd. The apoplastic barriers, exo- and endodermis, were developed relatively close to the apex. In both layers the first ontogenetic stage, the Casparian band development, was followed by the second stage, the suberin lamellae deposition. This process started in the endodermis, preferentially against phloem poles, which is a common phenomenon also in other plant species.
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