Hydroponic Screening of Shrub Willow (Salix Spp.) for Arsenic Tolerance and Uptake

Abstract

Shrub willows have demonstrated potential in many types of phytoremediation applications. Hydroponic culture was used to assess arsenic (As) tolerance and uptake by four shrub willow clones and to determine the effects of phosphate on As accumulation. After 4 weeks of growth in the absence of As, plants received one of four treatments: 0.25X Hoagland's minus P (−P), 0.25X Hoagland's minus P plus 100 μM arsenate (As100(−P)), 0.25X Hoagland's minus P plus 250 μM arsenate (As250(−P)), and 0.25X Hoagland's plus 250 μM arsenate (As250(+P)). Except for treatment As250(+P), phosphate was excluded due to its tendency to interfere with As uptake. After 3 weeks of treatment, plants were separated into root, leaf, and stem tissues. Biomass production and transpiration were used to quantify As tolerance. There was wide variation among clones in As tolerance and uptake. The presence of phosphate in solution alleviated the negative impacts of As on biomass and transpiration and also increased aboveground As accumulation, suggesting that phosphate may play a role in reducing toxicity and enhancing As uptake by willow shrubs. These findings offer insight into As tolerance and uptake in Salix spp. and add to the growing body of evidence supporting the use of shrub willow for phytoremediation.

KEY WORDS:

• arsenate
• phosphate
• phosphate transporters
• phytoremediation

ACKNOWLEDGEMENTS

The authors are grateful for financial support from a grant by the United States Department of Agriculture Cooperative State Research, Education, and Extension Service McIntire-Stennis Cooperative Forestry Research Program to Dr. Lawrence B. Smart. They thank Deborah Driscoll, Anthony Eallonardo, Dr. Timothy Volk, Dr. Thomas Horton, and Charles Schirmer for helpful advice, and Susan Loeffler-Harter and Michael Johnson for excellent technical assistance.