Relative Abundance of Nickel in the Leaf Epidermis of Eight Hyperaccumulators: Evidence that the Metal is Excluded from both Guard Cells and Trichomes

Scanning electron microscopy combined with X-ray microanalysiswas used to localize the sites of nickel accumulation on theleaf epidermis of eight nickel accumulators grown on ultramaficsoils in Greece. In all species, nickel was excluded from guardcells, and in species possessing hairy leaves (seven out ofeight) nickel was excluded from the hairs. In some species themetal was present in subsidiary cells, yet at low levels, whilethe sites of higher accumulation were epidermal cells away fromstomata. Results indicate that nickel is not compatible withthe functions and development of certain epidermal cell types.Copyright 2000 Annals of Botany Company Brassicaceae, epidermis, metal hyperaccumulators, microanalysis, serpentine plants