Mature trichome is the earliest sequestration site of Cd ions in Arabidopsis thaliana leaves

Sequestration of heavy metals by plants in non-glandular leaf trichomes is important for survival in toxic soils and has the potential for environmental remediation. Although heavy metals are particularly toxic to many plants during development, the integration of sequestration into the developmental timecourse is unknown. We tested the hypothesis that plants preferentially sequester heavy metals into mature trichomes by investigating the timecourse of Cd(2+) ions into the leaves of the model plant Arabidopsis thaliana. Results supported the hypothesis and surprisingly showed no Cd(2+) ions accumulated in earlier trichome development stages and that sequestration and release by mature trichomes were periodic and dynamic. Studies in mutants suggested that these dynamics were governed by the trichome's secondary cell wall, which matures late in development. Results suggest a developmentally timed pathway for excluding heavy metal toxins and the existence of mechanisms for controlled release that may relate to proposed functions of mature trichomes in plants.