Boron Accumulation and Toxicity in Hybrid Poplar (Populus nigra × euramericana)

摘要

Poplars accumulate high B concentrations and are thus used for the phytomanagement of B contaminated soils. Here, we performed pot experiments in which Populus nigra x euramer- icana were grown on a substrate with B concentrations ranging from 13 to 280 mg kg~(-1) as H_3BO_3 Salix vimmalis,Brasssica juncea, and Lupmtu atbut were grown under some growing conditions for comparison. Poplar growl]) was unaffected at soil B treatment levels up to 93 mg kg"'. Growth was progressively reduced at levels of 168 and 280 mgkg~(-1).None of the other species survived at theese substrate B levels,At leaf B cencentrations <900 mg kg~(-1) only <10% of the poplar leaf area showed signs of toxMty. Neutron ndtogaphy reveded ft* ddorotic k*f tissues had B concentrations of 1000-2000 mg kg~(-1), while necrotk tissues had >2000 mg kg~(-1). Average B conceattitionsofupM3500mgkg~(-1) were found in leaves, while spots within leaves had concentrations >7000 mg kg"', showing that B aocanrasation in leaf tissue continued even after the onset ofnecrosis. The B accumulation ability of P. nigra x cunmuriama is associated with Bhypertolerance in the living tissue and storage of B in dead leaf tissue.