Examination of the distribution of arsenic in hydrated and fresh cowpea roots using two- and three-dimensional techniques.
Arsenic (As) is considered to be the environmental contaminant of greatest concern due to its potential accumulation in the food chain and in humans. Using novel synchrotron-based x-ray fluorescence techniques (including sequential computed tomography), short-term solution culture studies were used to examine the spatial distribution of As in hydrated and fresh roots of cowpea (Vigna unguiculata 'Red Caloona') seedlings exposed to 4 or 20 µm arsenate [As(V)] or 4 or 20 µm arsenite. For plants exposed to As(V), the highest concentrations were observed internally at the root apex (meristem), with As also accumulating in the root border cells and at the endodermis. When exposed to arsenite, the endodermis was again a site of accumulation, although no As was observed in border cells. For As(V), subsequent transfer of seedlings to an As-free solution resulted in a decrease in tissue As concentrations, but growth did not improve. These data suggest that, under our experimental conditions, the accumulation of As causes permanent damage to the meristem. In addition, we suggest that root border cells possibly contribute to the plant's ability to tolerate excess As(V) by accumulating high levels of As and limiting its movement into the root.
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia. p.kopittke@uq.edu.au
Peter M
PM
Kopittke
Martin D
MD
de Jonge
Neal W
NW
Menzies
Peng
P
Wang
Erica
E
Donner
Brigid A
BA
McKenna
David
D
Paterson
Daryl L
DL
Howard
Enzo
E
Lombi
D001151:Arsenic / Q000378:metabolism* / Q000633:toxicity; D018533:Biomass; D007887:Fabaceae / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D014054:Tomography / Q000379:methods*; D014867:Water / Q000502:physiology*
D014867:Water; D001151:Arsenic