Ecological restoration of salty agricultural soils: role of compartmentation of boron and salts for poplar tree tolerance
With a quickly growing world
population and raising demand for agricultural products, the sustained production
of irrigated agricultural soils is a major issue. Crop production is already
impeded or at least threatened as a consequence of soil salinization following
decades of massive irrigation in many places with arid climates, e.g. San Joaquin Valley
in Central California. In such areas, excessive
amounts of irrigated water exceeding the plants’ evapotranspiration rates and
growth requirements have accelerated the breakdown of sedimentary shale bedrock
and increased the leaching of various natural-occuring elements like selenium
(Se) and boron (B) that can be toxic to animals or plants. In addition, high
water tables rising during the winter can then move the leachates up to the
higher soil horizons, where they precipitate forming a toxic salt crust. Subsequent
irrigation then leads to the production of contaminated drainage water
(containing these salts), which poses a threat for aquifers and ecosystem. Sustainable
solutions for disposal/reuse of contaminated drainage water and promoting
ecosystem restoration have been developed by the USDA-ARS Water Management
Research Laboratory with a world-wide application potential. A research unit
led by Dr. Gary Bañuelos has identified and tested several B and salt-tolerant
varieties from different plant species using small-scale experiments, as well
as field assays in an attempt to identify alternative plants/trees that are
able to safely utilize the contaminated water. Promising crops have been
selected from biofuel-producing crops, e.g. mustard and for ecosystem
restoration, which include poplar trees.
The aims of the present Master research project are to investigate the
compartmentation based-mechanisms contributing to the observed tolerance in
foliage of poplar trees grown under adverse growing conditions. Leaf material sampled
from trees growing in California
in September 2010 will be investigated with different methods by light and
electron microscopy techniques. Contaminants including B, sodium (Na), chlorine
(Cl) and several metals will be mapped and quantified in their subcellular,
cell, tissue and leaf compartments and the detoxification and stress reactions
analysed. Findings will be compared with elemental concentrations, soil
contamination and tree growth analysed in other modules of the project. Hence,
the Master candidate will closely collaborate with a US student coming in 2011 for a six
months fellowship to perform the analyses. In direct connection to the Master
and after its completion, a training period (at least 2-3 months) within Dr.
Gary Bañuelos team will be eventually organised - subjected to exchange grant
availability and candidate interest - to further study other aspects of poplar
tolerance to salt contamination and soil salinization under field conditions.
Scientific
methods
- Microlocalisation of soil
contaminants: electron dispersive X-ray microanalysis / neutron radiography
- Detoxification, tolerance and
stress reactions: Light, fluorescence and transmission electron microscopy
Mentors
- Dr. Pierre Vollenweider (microscopical analysis / microscopy project leader)
WSL, Birmensdorf, Switzerland
- Dr. Gary Bañuelos (US training period / poplar project leader)
USDA-ARS Water Management Res. Lab., Parlier, California
- Dr. Andres Kaech (microscopy project associate)
University of Zurich, Zurich, Switzerland
- Prof. James P. Prince (poplar project associate)
California State University, Fresno, California
- Dr. Davis W. Cheng (poplar project associate)
California State University, Fresno, California
- Dr. Christopher Buser (microscopy project associate)
California State University, Berkeley, California
Contact
Tel: ++41 44 739 24 35, Fax: ++41 44 739 22 54, E-Mail: vollenwe@wsl.ch
