Anatomical, biochemical and morphological responses of poplar Populus deltoides clone Lux to Zn excess

• Zn did not influence the biomass of poplar (P. deltoides, clone Lux).
• The concentration of Zn in leaf tissues was significantly increased.
• Zn modified the development of apoplasmic barriers in roots.
• Zn is accumulated mostly in the root peripheral tissues.
• Zn markedly affected the leaf anatomy and mesophyll cells ultrastructure.

The present study investigated the effect of excess Zn on growth and development of poplar (Populus deltoides Bartr. ex Marsh.) clone Lux. Although Zn did not greatly influence the production of plant biomass, the concentration of Zn in leaf tissues was significantly increased. This corresponds with shifted development of final stage of apoplasmic barriers in Zn-treated roots more distant from the root apex when compared with control roots. In the same time, various symptoms of Zn toxicity have been observed at anatomical and ultrastructural level, both in roots and in leaves. Cellular localization of Zn in roots by cryo-SEM and energy-dispersive X-ray microanalysis revealed that Zn is accumulated mostly in the root peripheral tissues and decreased toward to the central cylinder. Increased uptake and accumulation of Zn in leaves without visible reduction of growth makes this particular poplar clone an interesting candidate for future study aimed to phytoremediation of Zn-polluted sites.