Accumulation of zinc and cadmium and localization of zinc in Picris divaricata Vant. |
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| Institution: | 1. Department of Applied Sciences & Allied Health, Ara Institute of Canterbury, PO Box 540, Christchurch 8140, New Zealand;2. School of Biological Sciences, University of Canterbury, Christchurch 8140, New Zealand;1. Biobehavioral Sciences Lab, Warfighter Performance Department, Naval Health Research Center, 140 Sylvester Road, San Diego, CA, USA;2. School of Exercise and Nutritional Sciences, San Diego State University, ENS Building Room 351, 5500 Campanile Drive, San Diego, CA, USA;3. Institute for Interdisciplinary Salivary Bioscience Research, Arizona State University, 550 E. Orange Street, Tempe, AZ, USA;4. Department of Psychology, 1227 University of Oregon, Eugene, OR, USA;5. Johns Hopkins School of Nursing and Bloomberg School of Public Health, 3400 North Charles Street, Baltimore, MD, USA |
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| Abstract: | Picris divaricata Vant., a plant species native to subtropical China, was recently identified as the first Cd/Zn hyperaccumulator from Asteraceae. P. divaricata was grown from wild collected seed for 4 months in a series of pH adjusted test soils with added Zn levels 0–7000 mg kg−1 and Cd levels 0–150 mg kg−1. Plants did not hyperaccumulate Zn (threshold >3000 μg g−1) and weakly hyperaccumulated Cd with little or no dose–response.P. divaricata has multicellular simple trichomes concentrated on the leaf margins and midrib. X-ray analysis showed that Zn was concentrated in larger trichomes and epidermal cells adjacent to the trichome but virtually absent in other leaf tissues. Within the trichomes, Zn was localized in ovate spots around the tips of individual cells. These tips and other locations in the trichome cell contained black electron dense material when examined with transmission electron microscopy, some of which was identified as SiO2. Silicon and Mn were concentrated in the same areas as Zn. Si has been previously associated with alleviating Zn, Mn and Cd toxicity. Our results support this observation and further investigation is warranted.Calcium and P were concentrated in the distal tips of trichomes, similar to patterns previously observed for calcicole plants grown in elevated Ca soils. Overall, nonsecretory trichomes from many plant families may have a common origin as tissues adapted to handle a variety of environmental metals. |
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