In the most recent issue of the International Journal of Phytoremediation there is a paper titled "Phytoextraction and Accumulation of Boron and Selenium by Poplar Hybred Clones". The work described in the paper focus on the effects of salinity on the uptake of B and Se. It appears that with the most poplars an EC of between 7 and 15 is about the maximum you can have before you have leaf absession. Only one hybrid could withstand the higher salinity (>15). I know this work focuses on B and Se; however, the salinity data may be of some use to your selection.

Paul C. Deutsch, CPSS
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